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MICROBIOLOGY (210 journals)                  1 2 3     

Acta Microbiologica et Immunologica Hungarica     Full-text available via subscription   (Followers: 6)
Addiction Genetics     Open Access   (Followers: 3)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 14)
Advances in Microbiology     Open Access   (Followers: 15)
Advances in Molecular Imaging     Open Access   (Followers: 3)
African Journal of Clinical and Experimental Microbiology     Open Access   (Followers: 1)
African Journal of Microbiology Research     Open Access   (Followers: 1)
American Journal of Infectious Diseases and Microbiology     Open Access   (Followers: 13)
American Journal of Microbiological Research     Open Access  
American Journal of Microbiology     Open Access   (Followers: 14)
American Journal of Molecular Biology     Open Access   (Followers: 3)
American Journal of Stem Cell Research     Open Access   (Followers: 1)
Annals of Clinical Microbiology and Antimicrobials     Open Access   (Followers: 5)
Annals of Microbiology     Hybrid Journal   (Followers: 7)
Annual Review of Microbiology     Full-text available via subscription   (Followers: 21)
Antimicrobial Agents and Chemotherapy     Full-text available via subscription   (Followers: 15)
Applied and Environmental Microbiology     Full-text available via subscription   (Followers: 24)
Applied Biochemistry and Microbiology     Hybrid Journal   (Followers: 7)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 23)
Archives of Microbiology     Hybrid Journal   (Followers: 3)
Avicenna Journal of Clinical Microbiology and Infection     Open Access  
Beneficial Microbes     Full-text available via subscription   (Followers: 2)
Bio-Research     Full-text available via subscription  
BioArchitecture     Full-text available via subscription  
Biocell     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 4)
Biomedical Research     Open Access   (Followers: 3)
BioMolecular Concepts     Full-text available via subscription   (Followers: 2)
Biomolecules     Open Access   (Followers: 1)
BMC Microbiology     Open Access   (Followers: 6)
Brazilian Journal of Microbiology     Open Access   (Followers: 2)
Canadian Journal of Infectious Diseases & Medical Microbiology     Hybrid Journal   (Followers: 1)
Canadian Journal of Microbiology     Full-text available via subscription   (Followers: 3)
Cell Biology : Research & Therapy     Partially Free  
Cell Host & Microbe     Full-text available via subscription   (Followers: 7)
Cell Medicine     Open Access  
Cell Regeneration     Open Access  
Cell Stem Cell     Full-text available via subscription   (Followers: 19)
Cells     Open Access   (Followers: 1)
Cellular & Molecular Immunology     Hybrid Journal   (Followers: 8)
Cellular Microbiology     Hybrid Journal   (Followers: 4)
Cheese: Chemistry, Physics and Microbiology     Full-text available via subscription   (Followers: 2)
Chimerism     Full-text available via subscription  
Clinical Microbiology and Infection     Hybrid Journal   (Followers: 13)
Clinical Microbiology Newsletter     Hybrid Journal   (Followers: 3)
Clinical Microbiology Reviews     Full-text available via subscription   (Followers: 10)
Comparative Immunology, Microbiology and Infectious Diseases     Hybrid Journal   (Followers: 8)
Computational Molecular Bioscience     Open Access   (Followers: 1)
Continental Journal of Microbiology     Open Access   (Followers: 3)
Critical Reviews in Microbiology     Hybrid Journal   (Followers: 6)
Current Issues in Molecular Biology     Open Access  
Current Microbiology     Hybrid Journal   (Followers: 5)
Current Molecular Imaging     Hybrid Journal  
Current Opinion in Microbiology     Hybrid Journal   (Followers: 15)
Current Tissue Engineering     Hybrid Journal   (Followers: 1)
Current Topics in Microbiology and Immunology     Hybrid Journal   (Followers: 4)
Diagnostic Microbiology and Infectious Disease     Hybrid Journal   (Followers: 3)
Disease and Molecular Medicine     Open Access   (Followers: 1)
DNA Barcodes     Open Access  
Egyptian Journal of Biochemistry and Molecular Biology     Full-text available via subscription  
Emerging Microbes & Infections     Open Access   (Followers: 2)
Environmental Microbiology     Hybrid Journal   (Followers: 7)
Environmental Microbiology Reports     Hybrid Journal   (Followers: 3)
Enzyme and Microbial Technology     Hybrid Journal   (Followers: 5)
Epigenetics of Degenerative Diseases     Open Access   (Followers: 3)
European Journal of Clinical Microbiology & Infectious Diseases     Hybrid Journal   (Followers: 10)
European Journal of Microbiology and Immunology     Open Access   (Followers: 6)
Experimental and Molecular Pathology     Hybrid Journal   (Followers: 1)
Fems Immunology & Medical Microbiology     Hybrid Journal   (Followers: 6)
Fems Microbiology Ecology     Hybrid Journal   (Followers: 6)
Fems Microbiology Letters     Hybrid Journal   (Followers: 13)
Fems Microbiology Reviews     Hybrid Journal   (Followers: 16)
Folia Histochemica et Cytobiologica     Open Access  
Folia Microbiologica     Hybrid Journal   (Followers: 1)
Food Microbiology     Hybrid Journal   (Followers: 11)
Frontiers in Cell and Developmental Biology     Open Access   (Followers: 1)
Frontiers in Cellular and Infection Microbiology     Open Access   (Followers: 2)
Frontiers in Cellular Neuroscience     Open Access  
Frontiers in Microbiology     Open Access   (Followers: 5)
Frontiers in Molecular Neuroscience     Open Access  
Future Microbiology     Full-text available via subscription   (Followers: 2)
Future Virology     Full-text available via subscription   (Followers: 4)
Gene Expression     Full-text available via subscription  
Genetica si Biologie Moleculara     Open Access   (Followers: 1)
Genetics and Molecular Research     Open Access   (Followers: 3)
Geomicrobiology Journal     Hybrid Journal   (Followers: 1)
Gut Microbes     Full-text available via subscription   (Followers: 2)
Indian Journal of Microbiology     Hybrid Journal   (Followers: 1)
Indian Journal of Pathology and Microbiology     Open Access   (Followers: 1)
Infection Ecology & Epidemiology     Open Access   (Followers: 6)
International Arabic Journal of Antimicrobial Agents     Open Access   (Followers: 4)
International Journal of Antimicrobial Agents     Hybrid Journal   (Followers: 2)
International Journal of Bacteriology     Open Access  
International Journal of Bioassays     Open Access   (Followers: 6)
International Journal of Biotechnology and Molecular Biology Research     Open Access  
International Journal of Food Microbiology     Hybrid Journal   (Followers: 11)
International Journal of Infection and Microbiology     Open Access   (Followers: 1)
International Journal of Medical Microbiology     Hybrid Journal   (Followers: 6)
International Journal of Systematic and Evolutionary Microbiology     Full-text available via subscription   (Followers: 2)
International Microbiology     Open Access   (Followers: 2)

        1 2 3     

Journal Cover International Journal of Food Microbiology
   Journal TOC RSS feeds Export to Zotero [13 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0168-1605
     Published by Elsevier Homepage  [2566 journals]   [SJR: 1.386]   [H-I: 108]
  • Multilocus sequence typing reveals genetic diversity of foodborne
           Arcobacter butzleri isolates in the North of Spain
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Rodrigo Alonso , Cecilia Girbau , Irati Martinez-Malaxetxebarria , Aurora Fernández-Astorga
      The emerging pathogen Arcobacter butzleri is being increasingly isolated from different animal food products but the routes of its transmission to human are not well established yet. Typing methods would be useful in gaining such knowledge. Here we report the great genetic diversity observed among A. butzleri isolates from different food products. Forty-five isolates were analyzed by Multilocus Sequence Typing (MLST). A total of 157 alleles were identified across all seven loci, ranging from 16 alleles at glnA to 31 at glyA. MLST differentiated the isolates into 34 sequence types (STs), with the majority of isolates containing a unique sequence type. Seventy-four new alleles were identified, which resulted in the assignment of 33 new STs. No association of alleles or STs with food source was observed. For the first time, lateral gene transfer from Arcobacter skirrowii to A. butzleri at the glyA locus is also reported.


      PubDate: 2014-09-28T20:00:26Z
       
  • Co-occurrence of free-living protozoa and foodborne pathogens on
           dishcloths: Implications for food safety
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): N. Chavatte , J. Baré , E. Lambrecht , I. Van Damme , M. Vaerewijck , K. Sabbe , K. Houf
      In the present study, the occurrence of free-living protozoa (FLP) and foodborne bacterial pathogens on dishcloths was investigated. Dishcloths form a potentially important source of cross-contamination with FLP and foodborne pathogens in food-related environments. First various protocols for recovering and quantifying FLP from dishcloths were assessed. The stomacher technique is recommended to recover flagellates and amoebae from dishcloths. Ciliates, however, were more efficiently recovered using centrifugation. For enumeration of free-living protozoa on dishcloths, the Most Probable Number method is a convenient method. Enrichment was used to assess FLP diversity on dishcloths (n=38). FLP were found on 89% of the examined dishcloths; 100% of these tested positive for amoebae, 71% for flagellates and 47% for ciliates. Diversity was dominated by amoebae: vahlkampfiids, vannellids, Acanthamoeba spp., Hyperamoeba sp. and Vermamoeba vermiformis were most common. The ciliate genus Colpoda was especially abundant on dishcloths while heterotrophic nanoflagellates mainly belonged to the genus Bodo, the glissomonads and cercomonads. The total number of FLP in used dishcloths ranged from 10 to 104 MPN/cm2. Flagellates were the most abundant group, and ciliates the least abundant. Detergent use was identified as a prime determinant of FLP concentrations on used dishcloths. Bacterial load on dishcloths was high, with a mean total of aerobic bacteria of 7.47log10 cfu/cm2. Escherichia coli was detected in 68% (26/38) of the used dishcloths, with concentrations up to 4log10 cfu/cm2. Foodborne pathogens including Staphylococcus aureus (19/38), Arcobacter butzleri (5/38) and Salmonella enterica subsp. enterica ser. Halle (1/38) were also present. This study showed for the first time that FLP, including some opportunistic pathogens, are a common and diverse group on dishcloths. Moreover, important foodborne pathogens are also regularly recovered. This simultaneous occurrence makes dishcloths a potential risk factor for cross-contamination and a microbial niche for bacteria–FLP interactions.


      PubDate: 2014-09-28T20:00:26Z
       
  • Cold stress improves the ability of Lactobacillus plantarum L67 to survive
           freezing
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Sooyeon Song , Dong-Won Bae , Kwangsei Lim , Mansel W. Griffiths , Sejong Oh
      The stress resistance of bacteria is affected by the physiological status of the bacterial cell and environmental factors such as pH, salts and temperature. In this study, we report on the stress response of Lactobacillus plantarum L67 after four consecutive freeze–thaw cycles. The cold stress response of the cold-shock protein genes (cspC, cspL and cspP) and ATPase activities were then evaluated. The cold stress was adjusted to 5°C when the bacteria were growing at the mid-exponential phase. A comparative proteomic analysis was performed with two-dimensional gel electrophoresis (2D SDS-PAGE) and a matrix assisted laser desorption/ionization-mass spectrometer. Only 56% of the L. plantarum L67 cells without prior exposure to cold stress survived after four consecutive freeze–thaw cycles. However, 78% of the L. plantarum L67 cells that were treated with cold stress at 5°C for 6h survived after freeze–thaw conditions. After applying cold stress to the culture for 6h, the cells were then stored for 60days at 5°C, 25°C and 35°C separately. The cold-stressed culture of L. plantarum L67 showed an 8% higher viability than the control culture. After applying cold stress for 6h, the transcript levels of two genes (cspP and cspL) were up-regulated 1.4 (cspP) and 1.2 (cspL) times compared to the control. However, cspC was not up-regulated. A proteomic analysis showed that the proteins increased after a reduction of the incubation temperature to 5°C. The importance of the expression of 13 other relevant proteins was also determined through the study. The exposure of L. plantarum cells to low temperatures aids their ability to survive through subsequent freeze–thaw processes and lyophilization.


      PubDate: 2014-09-28T20:00:26Z
       
  • Inactivation of Escherichia coli O157:H7 in biofilm on food-contact
           surfaces by sequential treatments of aqueous chlorine dioxide and drying
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Jihyun Bang , Ayoung Hong , Hoikyung Kim , Larry R. Beuchat , Min Suk Rhee , Younghoon Kim , Jee-Hoon Ryu
      We investigated the efficacy of sequential treatments of aqueous chlorine and chlorine dioxide and drying in killing Escherichia coli O157:H7 in biofilms formed on stainless steel, glass, plastic, and wooden surfaces. Cells attached to and formed a biofilm on wooden surfaces at significantly (P ≤0.05) higher levels compared with other surface types. The lethal activities of sodium hypochlorite (NaOCl) and aqueous chlorine dioxide (ClO2) against E. coli O157:H7 in a biofilm on various food-contact surfaces were compared. Chlorine dioxide generally showed greater lethal activity than NaOCl against E. coli O157:H7 in a biofilm on the same type of surface. The resistance of E. coli O157:H7 to both sanitizers increased in the order of wood>plastic>glass>stainless steel. The synergistic lethal effects of sequential ClO2 and drying treatments on E. coli O157:H7 in a biofilm on wooden surfaces were evaluated. When wooden surfaces harboring E. coli O157:H7 biofilm were treated with ClO2 (200μg/ml, 10min), rinsed with water, and subsequently dried at 43% relative humidity and 22°C, the number of E. coli O157:H7 on the surface decreased by an additional 6.4CFU/coupon within 6h of drying. However, when the wooden surface was treated with water or NaOCl and dried under the same conditions, the pathogen decreased by only 0.4 or 1.0logCFU/coupon, respectively, after 12h of drying. This indicates that ClO2 treatment of food-contact surfaces results in residual lethality to E. coli O157:H7 during the drying process. These observations will be useful when selecting an appropriate type of food-contact surfaces, determining a proper sanitizer for decontamination, and designing an effective sanitization program to eliminate E. coli O157:H7 on food-contact surfaces in food processing, distribution, and preparation environments.


      PubDate: 2014-09-28T20:00:26Z
       
  • Salmonella source attribution based on microbial subtyping: Does including
           data on food consumption matter'
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Lapo Mughini-Gras , Wilfrid van Pelt
      Source attribution based on microbial subtyping is being performed in many countries to ascertain the main reservoirs of human salmonellosis and to assess the impact of food safety interventions. To account for differences in exposure, the amount of food available for consumption within a country is often included in Salmonella source attribution models along with the level of contamination. However, not all foods have an equal probability of serving as vehicles for salmonellas, as some foods are more likely to be consumed raw/undercooked than others, posing a relatively higher risk. Using Salmonella data from the Netherlands in 2001–2004, this study aims at elucidating whether and how the incorporation of food consumption data in two source attribution models – the (modified) Dutch and Hald models – affects their attributions. We also propose the incorporation of an additional parameter to weight the amount of food consumed by its likelihood to be consumed raw/undercooked by the population. Incorporating the amount of food consumed caused a drastic change in the ranking of the top reservoirs in the Dutch model, but not in the Hald model, which proved to be insensitive to additional weightings given that its source-dependent factor can account for both food consumption and the ability for foods to serve as vehicles for salmonellas. Compared to attributions without food consumption, the Dutch model including the amount of food consumed showed an increase in the percentage of cases attributable to pigs and a decrease in that of layers/eggs, which became the second reservoir, after pigs. This was not consistent with established knowledge indicating that layers/eggs, rather than pigs, were the main reservoir of human salmonellosis in that period. By incorporating the additional weight reflecting the likelihood for different foods to be consumed raw/undercooked, the attributions of the Dutch model were effectively adjusted, both in terms of ranking and percent contributions of the different reservoirs. We concluded that incorporating food consumption data in the Dutch model can significantly affect the results. Therefore, such data should be either excluded from this model or used together with an additional weight able to adjust the amount of food consumed by its likelihood to be consumed insufficiently cooked. This may help identifying the correct reservoirs, allowing attributions to more closely reflect the real chance for a given food to serve as a vehicle for salmonellas. Conversely, the Hald model works properly irrespective of inclusion of food consumption data.


      PubDate: 2014-09-28T20:00:26Z
       
  • Identification of lactobacilli with inhibitory effect on biofilm formation
           by pathogenic bacteria on stainless steel surfaces
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Fatma Ait Ouali , Imad Al Kassaa , Benoit Cudennec , Marwan Abdallah , Farida Bendali , Djamila Sadoun , Nour-Eddine Chihib , Djamel Drider
      Two hundred and thirty individual clones of microorganisms were recovered from milk tanks and milking machine surfaces at two distinct farms (Bejaja City, Algeria). Of these clones, 130 were identified as lactic acid bacteria (LAB). In addition Escherichia coli, Salmonella, Staphylococcus aureus and Pseudomonas aeruginosa species were identified in the remaining 100 isolates—spoilage isolate. These isolates were assayed for ability to form biofilms. S. aureus, Lactobacillus brevis strains LB1F2, LB14F1 and LB15F1, and Lactobacillus pentosus strains LB2F2 and LB3F2 were identified as the best biofilm formers. Besides, these LAB isolates were able to produce proteinaceous substances with antagonism against the aforementioned spoilage isolates, when grown in MRS or TSB-YE media. During the screening, L. pentosus LB3F2 exhibited the highest antibacterial activity when grown in TSB-YE medium at 30°C. Additionally, L. pentosus LB3F2 was able to strongly hamper the adhesion of S. aureus SA3 on abiotic surfaces as polystyrene and stainless steel slides. LAB isolates did not show any hemolytic activity and all of them were sensitive to different families of antibiotic tested. It should be pointed out that LB3F2 isolate was not cytotoxic on the intestinal cells but could stimulate their metabolic activity. This report unveiled the potential of LB1F2, LB14F1, LB15F1, LB2F2, and LB3F2 isolates to be used as natural barrier or competitive exclusion organism in the food processing sector as well as a positive biofilm forming bacteria.


      PubDate: 2014-09-28T20:00:26Z
       
  • Adhesion of Salmonella Enteritidis and Listeria monocytogenes on stainless
           steel welds
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Letícia Sopeña Casarin , Adriano Brandelli , Fabrício de Oliveira Casarin , Paulo Azevedo Soave , Cesar Henrique Wanke , Eduardo Cesar Tondo
      Pathogenic microorganisms are able to adhere on equipment surfaces, being possible to contaminate food during processing. Salmonella spp. and Listeria monocytogenes are important pathogens that can be transmitted by food, causing severe foodborne diseases. Most surfaces of food processing industry are made of stainless steel joined by welds. However currently, there are few studies evaluating the influence of welds in the microorganism's adhesion. Therefore the purpose of the present study was to investigate the adhesion of Salmonella Enteritidis and L. monocytogenes on surface of metal inert gas (MIG), and tungsten inert gas (TIG) welding, as well as to evaluate the cell and surface hydrophobicities. Results demonstrated that both bacteria adhered to the surface of welds and stainless steel at same levels. Despite this, bacteria and surfaces demonstrated different levels of hydrophobicity/hydrophilicity, results indicated that there was no correlation between adhesion to welds and stainless steel and the hydrophobicity.


      PubDate: 2014-09-28T20:00:26Z
       
  • Safety assessment of greenhouse hydroponic tomatoes irrigated with
           reclaimed and surface water
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Francisco Lopez-Galvez , Ana Allende , Francisco Pedrero-Salcedo , Juan Jose Alarcon , Maria Isabel Gil
      The impact of reclaimed and surface water on the microbiological safety of hydroponic tomatoes was assessed. Greenhouse tomatoes were irrigated with reclaimed and surface water and grown on two hydroponic substrates (coconut fiber and rock wool). Water samples (n=208) were taken from irrigation water, with and without the addition of fertilizers and drainage water, and hydroponic tomatoes (n=72). Samples were analyzed for indicator microorganisms, generic Escherichia coli and Listeria spp., and pathogenic bacteria such as Salmonella spp. and Shiga-toxigenic E. coli (STEC), using multiplex real-time PCR (RT-PCR) after enrichment. The correlation between climatological parameters such as temperature and the levels of microorganisms in water samples was also determined. In irrigation water, generic E. coli counts were higher in reclaimed than in surface water whereas Listeria spp. numbers increased after adding the fertilizers in both water sources. In drainage water, no clear differences in E. coli and Listeria numbers were observed between reclaimed and surface water. No positive samples for STEC were found in irrigation water. Presumptive positives for Salmonella spp. were found in 7.7% of the water samples and 62.5% of these samples were reclaimed water. Salmonella-positive samples by RT-PCR could not be confirmed by conventional methods. Higher concentrations of E. coli were associated with Salmonella-presumptive positive samples. Climatological parameters, such as temperature, were not correlated with the E. coli and Listeria spp. counts. Tomato samples were negative for bacterial pathogens, while generic E. coli and Listeria spp. counts were below the detection limit. The prevalence of presumptive Salmonella spp. found in irrigation water (reclaimed and surface water) was high, which might present a risk of contamination. The absence of pathogens on greenhouse hydroponic tomatoes indicates that good agricultural practices (GAP) were in place, avoiding the microbial contamination of the fruit.


      PubDate: 2014-09-28T20:00:26Z
       
  • Antibacterial and physical effects of modified chitosan based-coating
           containing nanoemulsion of mandarin essential oil and three non-thermal
           treatments against Listeria innocua in green beans
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Renato Severino , Khanh Dang Vu , Francesco Donsì , Stephane Salmieri , Giovanna Ferrari , Monique Lacroix
      The antimicrobial activity against Listeria innocua of three different combined non-thermal treatments, along with the impact on color and texture on green bean samples, was evaluated. In this study a bioactive coating formulation based on modified chitosan containing 0.05% nanoemulsion of mandarin essential oil was tested in combination with γ-irradiation, UV-C and ozonated water treatments, and the results in terms of antimicrobial activity, color and texture changes, were evaluated during 14days storage. The combined coating and γ-irradiation treatment gave promising results, showing 3.3 log CFU/g initial microbial reduction, and exhibiting a strong synergistic antimicrobial effect. The treatment based on UV-C and coating formulation allowed a 3 log CFU/g reduction of initial L. innocua population on samples, showing a good residual antimicrobial activity and preventing loss of firmness and color changes during storage. The combined treatment of coating and ozonated water did not show any synergistic or additive antimicrobial effect, but they showed an impact on firmness and color. In conclusion UV-C and γ-irradiation treatments, in combination with the bioactive coating, represent an effective approach to control the growth of L. innocua on vegetable foods.


      PubDate: 2014-09-24T19:37:41Z
       
  • Antimicrobial properties of nisin after glycation with lactose,
           maltodextrin and dextran and the thyme oil emulsions prepared thereof
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Huaiqiong Chen , P. Michael Davidson , Qixin Zhong
      To clarify the reported conflicting antimicrobial activities of nisin after glycation, nisin was glycated with lactose, maltodextrin, and dextran at 70°C and 50% relative humidity for 1–24h. Nisin before and after glycation was studied for the first time to prepare thyme oil emulsions. The activity of glycated nisin and the thyme oil emulsions was tested in both tryptic soy broth (TSB) and 2% reduced fat milk. Results showed that nisin glycated with a smaller saccharide for a longer duration had a higher degree of glycation and the reduced number of positive charges lowered its antibacterial activity. The emulsified thyme oil had an additive effect with either glycated or native nisin against Listeria monocytogenes Scott A and Bacillus subtilis in TSB and 2% reduced fat milk. However, emulsions were less effective against L. monocytogenes Scott A in milk than same units of native nisin and same concentration of free thyme oil, likely due to the reduced availability of thymol and carvacrol, the main components of thyme oil. These results showed that glycation of nisin cannot broaden its antimicrobial activity and nisin is not a good compound to prepare emulsions of essential oils.


      PubDate: 2014-09-20T19:36:03Z
       
  • Bacteriophage P22 to challenge Salmonella in foods
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Paola Zinno , Chiara Devirgiliis , Danilo Ercolini , Duncan Ongeng , Gianluigi Mauriello
      In this study we considered the influence of phage addition on the fate of Salmonella enterica serovar Typhimurium in different foods. Phage P22 was applied to the following: liquid eggs, energy drinks, whole and skimmed milk, apple juice, chicken breast and chicken mince all spiked with its host, whose growth was monitored for 24 and 48h at 4°C. Appreciable host inactivation, generally in the order of 2 log cycles, was achieved compared to phage-free controls in all food matrices when 104 UFC/g host inoculum was used. Furthermore, wild food strains belonging to the serotypes Typhimurium, Enteritidis, Derby Give, Newport, Muenchen and Muenster were assayed towards phage P22. Only isolates of Salmonella Typhimurium as well as Salmonella Derby and Salmonella Enteritidis was inhibited by the presence of P22 phage. Additional challenge experiments were carried out by spiking liquid-eggs, chicken breast and chicken mince with mixes of wild Salmonella Typhimurium (at concentration of about 104 UFC/g) strains along with their relative phage P22. The results showed a reduction of 2–3 log cycles after 48h at 4°C depending on both mix of strains and the specific food. Overall, the results indicate that phages may be useful in the control of food-borne pathogens. The food matrices considered, the liquid more than the solid, do not seem to affect the phage ability of infection compared to similar tests performed in vitro.


      PubDate: 2014-09-20T19:36:03Z
       
  • Great interspecies and intraspecies diversity of dairy propionibacteria in
           the production of cheese aroma compounds
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Alyson L. Yee , Marie-Bernadette Maillard , Nathalie Roland , Victoria Chuat , Aurélie Leclerc , Tomislav Pogačić , Florence Valence , Anne Thierry
      Flavor is an important sensory property of fermented food products, including cheese, and largely results from the production of aroma compounds by microorganisms. Propionibacterium freudenreichii is the most widely used species of dairy propionibacteria; it has been implicated in the production of a wide variety of aroma compounds through multiple metabolic pathways and is associated with the flavor of Swiss cheese. However, the ability of other dairy propionibacteria to produce aroma compounds has not been characterized. This study sought to elucidate the effect of interspecies and intraspecies diversity of dairy propionibacteria on the production of aroma compounds in a cheese context. A total of 76 strains of Propionibacterium freudenreichii, Propionibacterium jensenii, Propionibacterium thoenii, and Propionibacterium acidipropionici were grown for 15days in pure culture in a rich medium derived from cheese curd. In addition, one strain each of two phylogenetically related non-dairy propionibacteria, Propionibacterium cyclohexanicum and Propionibacterium microaerophilum were included. Aroma compounds were analyzed using headspace trap-gas chromatography-mass spectrometry (GC–MS). An analysis of variance performed on GC–MS data showed that the abundance of 36 out of the 45 aroma compounds detected showed significant differences between the cultures. A principal component analysis (PCA) was performed for these 36 compounds. The first two axes of the PCA, accounting for 60% of the variability between cultures, separated P. freudenreichii strains from P. acidipropionici strains and also differentiated P. freudenreichii strains from each other. P. freudenreichii strains were associated with greater concentrations of a variety of compounds, including free fatty acids from lipolysis, ethyl esters derived from these acids, and branched-chain acids and alcohols from amino acid catabolism. P. acidipropionici strains produced less of these compounds but more sulfur-containing compounds from methionine catabolism. Meanwhile, branched-chain aldehydes and benzaldehyde were positively associated with certain strains of P. jensenii and P. thoenii. Moreover, the production of compounds with a common origin was correlated. Compound abundance varied significantly by strain, with fold changes between strains of the same species as high as in the order of 500 for a single compound. This suggests that the diversity of dairy propionibacteria can be exploited to modulate the flavor of mild cheeses.


      PubDate: 2014-09-20T19:36:03Z
       
  • Mupirocin-mucin agar for selective enumeration of Bifidobacterium bifidum
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Radko Pechar , Vojtech Rada , Lucia Parafati , Sarka Musilova , Vera Bunesova , Eva Vlkova , Jiri Killer , Jakub Mrazek , Vladimir Kmet , Roman Svejstil
      Bifidobacterium bifidum is a bacterial species exclusively found in the human intestinal tract. This species is becoming increasingly popular as a probiotic organism added to lyophilized products. In this study, porcine mucin was used as the sole carbon source for the selective enumeration of B. bifidum in probiotic food additives. Thirty-six bifidobacterial strains were cultivated in broth with mucin. Only 13 strains of B. bifidum utilized the mucin to produce acids. B. bifidum was selectively enumerated in eight probiotic food supplements using agar (MM agar) containing mupirocin (100mg/L) and mucin (20g/L) as the sole carbon source. MM agar was fully selective if the B. bifidum species was presented together with Bifidobacterium animalis subsp. lactis, Bifidobacterium breve, and Bifidobacterium longum subsp. longum species and with lactic acid bacteria (lactobacilli, streptococci). Isolated strains of B. bifidum were identified using biochemical, PCR, MALDI-TOF procedures and 16S rRNA gene sequencing. The novel selective medium was also suitable for the isolation of B. bifidum strains from human fecal samples.


      PubDate: 2014-09-16T19:21:42Z
       
  • Editorial Board
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190




      PubDate: 2014-09-16T19:21:42Z
       
  • ICFMH Announcment
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190




      PubDate: 2014-09-16T19:21:42Z
       
  • Control of Listeria monocytogenes in fresh cheese using protective lactic
           acid bacteria
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): M.C. Coelho , C.C.G. Silva , S.C. Ribeiro , M.L.N.E. Dapkevicius , H.J.D. Rosa
      In the past years, there has been a particular focus on the application of bacteriocins produced by lactic acid bacteria (LAB) in controlling the growth of pathogenic bacteria in foods. The aim of this study was to select LAB strains with antimicrobial activity, previously isolated from a traditional Azorean artisanal cheese (Pico cheese), in order to identify those with the greatest potential in reducing Listeria monocytogenes in fresh cheese. Eight bacteriocin producer strains identified as Lactococcus lactis (1) and Enterococcus faecalis (7) were tested. In general, the bacteriocin-producing strains presented a moderate growth in fresh cheese at refrigeration temperatures (4°C), increasing one log count in three days. They exhibited slow acidification capacity, despite the increased production of lactic acid displayed by some strains after 24h. Bacteriocin activity was only detected in the whey of fresh cheese inoculated with two Enterococcus strains, but all cheeses made with bacteriocin-producing strains inhibited L. monocytogenes growth in the agar diffusion bioassay. No significant differences were found in overall sensory evaluation made by a non-trained panel of 50–52 tasters using the isolates as adjunct culture in fresh cheese, with the exception of one Enterococcus strain. To test the effect of in situ bacteriocin production against L. monocytogenes, fresh cheese was made from pasteurized cows' milk inoculated with bacteriocin-producing LAB and artificially contaminated with approximately 106 CFU/mL of L. monocytogenes. The numbers of L. monocytogenes were monitored during storage of fresh cheese at refrigeration temperature (4°C) for up to 15days. All strains controlled the growth of L. monocytogenes, although some Enterococcus were more effective in reducing the pathogen counts. After 7days, this reduction was of approximately 4 log units compared to the positive control. In comparison, an increase of 4logCFU/mL in pathogen numbers was detected over the same period, in the absence of bacteriocin-producing LAB. The combination of two bacteriocin producing Enterococcus sp. optimized the reduction of L. monocytogenes counts in fresh cheese, reducing by approximately 5logunits after 7days. The present work demonstrates that using bacteriocin-producing strains in the manufacture of fresh cheese might contribute to preventing the growth of undesirable pathogenic bacteria such as L. monocytogenes. A blend of two strains demonstrated great potential as a protective culture for the cheese making process.


      PubDate: 2014-09-16T19:21:42Z
       
  • Genetic diversity of FLO1 and FLO5 genes in wine flocculent Saccharomyces
           cerevisiae strains
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Rosanna Tofalo , Giorgia Perpetuini , Paola Di Gianvito , Maria Schirone , Aldo Corsetti , Giovanna Suzzi
      Twenty-eight flocculent wine strains were tested for adhesion and flocculation phenotypic variability. Moreover, the expression patterns of the main genes involved in flocculation (FLO1, FLO5 and FLO8) were studied both in synthetic medium and in presence of ethanol stress. Molecular identification and typing were achieved by PCR-RFLP of the 5.8S ITS rRNA region and microsatellite PCR fingerprinting, respectively. All isolates belong to Saccharomyces cerevisiae species. The analysis of microsatellites highlighted the intraspecific genetic diversity of flocculent wine S. cerevisiae strains allowing obtaining strain-specific profiles. Moreover, strains were characterized on the basis of adhesive properties. A wide biodiversity was observed even if none of the tested strains were able to form biofilms (or ‘mats’), or to adhere to polystyrene. Moreover, genetic diversity of FLO1 and FLO5 flocculating genes was determined by PCR. Genetic diversity was detected for both genes, but a relationship with the flocculation degree was not found. So, the expression patterns of FLO1, FLO5 and FLO8 genes was investigated in a synthetic medium and a relationship between the expression of FLO5 gene and the flocculation capacity was established. To study the expression of FLO1, FLO5 and FLO8 genes in floc formation and ethanol stress resistance qRT-PCR was carried out and also in this case strains with flocculent capacity showed higher levels of FLO5 gene expression. This study confirmed the diversity of flocculation phenotype and genotype in wine yeasts. Moreover, the importance of FLO5 gene in development of high flocculent characteristic of wine yeasts was highlighted. The obtained collection of S. cerevisiae flocculent wine strains could be useful to study the relationship between the genetic variation and flocculation phenotype in wine yeasts.


      PubDate: 2014-09-16T19:21:42Z
       
  • Exploring the diversity of extremely halophilic archaea in food-grade
           salts
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Olivier Henriet , Jeanne Fourmentin , Bruno Delincé , Jacques Mahillon
      Salting is one of the oldest means of food preservation: adding salt decreases water activity and inhibits microbial development. However, salt is also a source of living bacteria and archaea. The occurrence and diversity of viable archaea in this extreme environment were assessed in 26 food-grade salts from worldwide origin by cultivation on four culture media. Additionally, metagenomic analysis of 16S rRNA gene was performed on nine salts. Viable archaea were observed in 14 salts and colony counts reached more than 105 CFU per gram in three salts. All archaeal isolates identified by 16S rRNA gene sequencing belonged to the Halobacteriaceae family and were related to 17 distinct genera among which Haloarcula, Halobacterium and Halorubrum were the most represented. High-throughput sequencing generated extremely different profiles for each salt. Four of them contained a single major genus (Halorubrum, Halonotius or Haloarcula) while the others had three or more genera of similar occurrence. The number of distinct genera per salt ranged from 21 to 27. Halorubrum had a significant contribution to the archaeal diversity in seven salts; this correlates with its frequent occurrence in crystallization ponds. On the contrary, Haloquadratum walsbyi, the halophilic archaea most commonly found in solar salterns, was a minor actor of the food-grade salt diversity. Our results indicate that the occurrence and diversity of viable halophilic archaea in salt can be important, while their fate in the gastrointestinal tract after ingestion remains largely unknown.


      PubDate: 2014-09-16T19:21:42Z
       
  • Membrane lipid composition and stress/virulence related gene expression of
           Salmonella Enteritidis cells adapted to lactic acid and trisodium
           phosphate and their resistance to lethal heat and acid stress
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Yishan Yang , Mellissa Irlianti Kadim , Wei Jie Khoo , Qianwang Zheng , Magdiel Inggrid Setyawati , Yu-Jin Shin , Seung-Cheol Lee , Hyun-Gyun Yuk
      This study evaluated the acid and heat resistance of Salmonella Enteritidis in simulated gastric fluid (pH2.0) and during thermal treatment (54–60°C), respectively, after adaptation to lactic acid (LA) or trisodium phosphate (TSP) at various pHs (pH5.3–9.0). The changes in membrane lipid composition and expression levels of RpoS and RpoH were examined to elucidate their roles in bacterial stress resistance. Transcriptional profile of several virulence-related genes was also analyzed. Results showed that LA-adapted cells at pH5.3 and 6.3 had higher acid and heat resistance than control cells and cells adapted to TSP at pH8.3 and 9.0. LA-adapted cells had the lowest ratio of unsaturated to saturated fatty acids, indicating that they might possess a less fluid membrane. It was observed that the expression levels of RpoH and RpoS were upregulated in TSP-adapted cells but not in LA-adapted cells. Thus, these results indicate that the increased acid and heat resistance of LA-adapted S. Enteritidis was possibly due to the decreased membrane fluidity instead of the upregulation of RpoS and RpoH. About 6.0, 2.1, and 2.46-fold upregulation of spvR, avrA, and hilA were observed in cells adapted to TSP at pH9.0, except sefA that had its highest expression level in the control cells, indicating that the expression of these virulence genes highly depends on environmental conditions. This is the first study to show that the alteration in the cytoplasmic membrane rather than RpoS and RpoH plays a more crucial role in conferring greater acid and heat resistance on LA-adapted S. Enteritidis, thus providing a better understanding on the bacterial stress response to acidic conditions.


      PubDate: 2014-09-16T19:21:42Z
       
  • Applicability of a Lactobacillus amylovorus strain as co-culture for
           natural folate bio-enrichment of fermented milk
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Jonathan Emiliano Laiño , Marianela Juarez del Valle , Graciela Savoy de Giori , Jean Guy Joseph LeBlanc
      The ability of 55 strains from different Lactobacillus species to produce folate was investigated. In order to evaluate folic acid productivity, lactobacilli were cultivated in the folate-free culture medium (FACM). Most of the tested strains needed folate for growth. The production and the extent of vitamin accumulation were distinctive features of individual strains. Lactobacillus amylovorus CRL887 was selected for further studies because of its ability to produce significantly higher concentrations of vitamin (81.2±5.4μg/L). The safety of this newly identified folate producing strain was evaluated through healthy experimental mice. No bacterial translocation was detected in liver and spleen after consumption of CRL887 during 7 days and no undesirable side effects were observed in the animals that received this strain. This strain in co-culture with previously selected folate producing starter cultures (Lactobacillus bulgaricus CRL871, and Streptococcus thermophilus CRL803 and CRL415) yielded a yogurt containing high folate concentrations (263.1±2.4μg/L); a single portion of which would provide 15% of the recommended dietary allowance. This is the first report where a Lactobacillus amylovorus strain was successfully used as co-culture for natural folate bio-enrichment of fermented milk.


      PubDate: 2014-09-16T19:21:42Z
       
  • Combined effects of benomyl and environmental factors on growth and
           expression of the fumonisin biosynthetic genes FUM1 and FUM19 by Fusarium
           verticillioides
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): A. Cruz , P. Marín , N. Magan , M.T. González-Jaén
      Fusarium verticillioides is predominantly responsible of fumonisin contamination of maize and other cereals in Mediterranean climatic regions. This study examined the interaction of the fungicide benomyl, at ED50 and ED90 concentrations (effective doses of benomyl to reduce growth by 50% and 90%, respectively), with a range of temperatures (20–35°C) and water potentials (−0.7, −2.8 and −7.0MPa) compatible with current and foreseen climate change scenarios for these regions on growth and fumonisin biosynthesis in in vitro assays. The expression of fumonisin biosynthetic genes (FUM1 and FUM19) was quantified by real time RT-PCR. FUM1 encodes a polyketide synthase and FUM19 an ABC-type transporter, located both in the fumonisin biosynthetic cluster. The ED50 and ED90 concentrations obtained at 25°C were 0.93mg/L and 3.30mg/L, respectively. Benomyl affected growth and fumonisin gene expression differently but it generally reduced fungal growth and fumonisin biosynthesis and both were significantly affected by temperature and water potential. This indicated that efficacy of benomyl might be compromised at certain conditions, although at similar or lower levels than other fungicides tested. Both fumonisin biosynthetic genes had similar expression patterns in all treatments and their correlation was positive and significant. The results suggested that Mediterranean climatic scenarios might suffer an additional negative impact of climate change by reducing the efficacy of antifungals used to control pathogens and toxigenic fungi.


      PubDate: 2014-09-16T19:21:42Z
       
  • Monitoring of Saccharomyces cerevisiae, Hanseniaspora uvarum, and
           Starmerella bacillaris (synonym Candida zemplinina) populations during
           alcoholic fermentation by fluorescence in situ hybridization
    • Abstract: Publication date: 17 November 2014
      Source:International Journal of Food Microbiology, Volume 191
      Author(s): Chunxiao Wang , Braulio Esteve-Zarzoso , Albert Mas
      Various molecular approaches have been applied as culture-independent techniques to monitor wine fermentations over the last decade. Among them, those based on RNA detection have been widely used for yeast cell detection, assuming that RNA only exists in live cells. Fluorescence in situ hybridization (FISH) targeting intracellular rRNA is considered a promising technique for the investigation of wine ecology. For the present study, we applied the FISH technique in combination with epifluorescence microscopy and flow cytometry to directly quantify populations of Saccharomyces cerevisiae, Hanseniaspora uvarum, and Starmerella bacillaris during alcoholic fermentations. A new specific probe that hybridizes with eight species of Hanseniaspora genus and a second probe specific for Starm. bacillaris were designed, and the conditions for their application to pure cultures, mixed cultures, and wine samples were optimized. Single and mixed fermentations were performed with natural, concentrated must at two different temperatures, 15°C and 25°C. The population dynamics revealed that the Sacch. cerevisiae population increased to 107–108 cells/ml during all fermentations, whereas H. uvarum and Starm. bacillaris tended to increase in single fermentations but remained at levels similar to their inoculations at 106 cells/ml in mixed fermentations. Temperature mainly affected the fermentation duration (slower at the lower temperature) but did not affect the population sizes of the different species. The use of these probes in natural wine fermentations has been validated.


      PubDate: 2014-09-16T19:21:42Z
       
  • Variable flocculation profiles of yeast strains isolated from cachaça
           distilleries
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Florencia Alvarez , Lygia Fátima da Mata Correa , Thalita Macedo Araújo , Bruno Eduardo Fernandes Mota , Luís Eduardo F. Ribeiro da Conceição , Ieso de Miranda Castro , Rogelio Lopes Brandão
      In cachaça production, the use of yeast cells as starters with predictable flocculation behavior facilitates the cell recovery at the end of each fermentation cycle. Therefore, the aim of this work was to explain the behavior of cachaça yeast strains in fermentation vats containing sugarcane through the determination of biochemical and molecular parameters associated with flocculation phenotypes. By analyzing thirteen cachaça yeast strains isolated from different distilleries, our results demonstrated that neither classic biochemical measurements (e.g., percentage of flocculation, EDTA sensitivity, cell surface hydrophobicity, and sugar residues on the cell wall) nor modern molecular approaches, such as polymerase chain reaction (PCR) and real-time PCR (q-PCR), were sufficient to distinctly classify the cachaça yeast strains according to their flocculation behavior. It seems that flocculation is indeed a strain-specific phenomenon that is difficult to explain and/or categorize by the available methodologies.


      PubDate: 2014-09-11T19:18:51Z
       
  • Genetic diversity and dynamics of bacterial and yeast strains associated
           to Spanish-style green table-olive fermentations in large manufacturing
           companies
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Helena Lucena-Padrós , Belén Caballero-Guerrero , Antonio Maldonado-Barragán , José Luis Ruiz-Barba
      We have genotyped a total of 1045 microbial isolates obtained along the fermentation time of Spanish-style green table olives from the fermentation yards (patios) of two large manufacturing companies in the Province of Sevilla, south of Spain. Genotyping was carried out using RAPD-PCR fingerprinting. In general, isolates clustered well into the relevant phylogenetic dendrograms, forming separate groups in accordance to their species adscription. We could identify which bacterial and yeast genotypes (strains) persisted throughout the fermentation at each patio. Also, which of them were more adapted to any of the three stages, i.e. initial, middle and final, described for this food fermentation. A number of genotypes were found to be shared by both patios. Fifty seven of these belonged to five different bacterial species, i.e. Lactobacillus pentosus, Lactobacillus paracollinoides/collinoides, Lactobacillus rapi, Pediococcus ethanolidurans and Staphylococcus sp., although most of them (51) belonged to L. pentosus. Four yeast genotypes were also shared, belonging to the species Candida thaimueangensis, Saccharomyces cerevisiae and Hanseniaspora sp. Two genotypes of L. pentosus were found to be grouped with those of two strains used in commercially available starter cultures, one of them bacteriocinogenic, which were used up to three years before this study in these patios, demonstrating the persistence of selected strains in this environment. Biodiversity was assessed though different indexes, including richness, diversity and dominance. A statistically significant decrease in biodiversity between the initial and final stages of the fermentation was found in both patios. However, values of biodiversity indexes in the fermenters were very similar, and no significant differences were found in the total biodiversity between both patios. This study allowed us to identify a range of well adapted strains (genotypes), especially those belonging to the lactic acid bacteria, which could be useful to improve safety and quality of table olive fermentations.


      PubDate: 2014-09-11T19:18:51Z
       
  • Food safety considerations in relation to Anisakis pegreffii in anchovies
           (Engraulis encrasicolus) and sardines (Sardina pilchardus) fished off the
           Ligurian Coast (Cinque Terre National Park, NW Mediterranean)
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Laura Serracca , Roberta Battistini , Irene Rossini , Annalaura Carducci , Marco Verani , Marino Prearo , Laura Tomei , Gabriella De Montis , Carlo Ercolini
      Engraulis encrasicolus and Sardina pilchardus are pelagic fishes of notable economic and gastronomic importance in the northwest Mediterranean (Ligurian Sea, Italy). The consumption of thermally unprocessed or lightly processed, marinated or salted anchovies and sardines presents a potential risk to acquire anisakiasis, a fish-borne parasitic disease in humans. Prevalence and abundance of Anisakis larvae in Engraulis encrasicolus and Sardina pilchardus from the Monterosso fishing grounds (Cinque Terre National Park, Ligurian Sea, Italy) were assessed, and the larvae were identified by morphological and PCR-RFLP methods. Anisakis larvae, all belonging to Anisakis pegreffii spp. were found in the visceral mass of 1050 anchovies (0.8% overall prevalence), whereas no Anisakis larvae were found in the 750 sardines examined. According to these data, the risk of acquiring anisakiasis from the consumption of raw or undercooked anchovies and sardines caught in the fishing area we investigated is very low.


      PubDate: 2014-09-11T19:18:51Z
       
  • Microbial succession of grass carp (Ctenopharyngodon idellus) filets
           during storage at 4°C and its contribution to biogenic amines'
           formation
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Hang Wang , Yongkang Luo , Heping Huang , Qian Xu
      Investigation on the microbial succession of grass carp filets during storage at 4°C was carried out. For identification, 16S rRNA genes of the isolated pure strains were sequenced and analyzed. Acinetobacter was dominant in fresh grass carp. Species from the genera Brevundimonas, Empedobacter, Pseudomonas, Microbacterium, Flavobacterium, Moraxella, Shewanella and Soonwooa were also detected at the initial day. The communities were dominated by Aeromonas and Acinetobacter after 6days. Aeromonas followed by Pseudomonas was the predominant genera at the end of shelf-life of grass carp, while other genera such as Shewanella, Acinetobacter, Flavobacteriaceae and Psychrobacter were present in smaller numbers. We investigated biogenic amines' (BAs) production by six strains isolated from spoiled grass carp filets. Shewanella putrefaciens showed significantly higher abilities to produce putrescine, than those from other genera. Aeromonas veronii revealed a strong ability to produce putrescine and cadaverine. However, Pseudomonas and Acinetobacter showed little ability to produce BAs.


      PubDate: 2014-09-11T19:18:51Z
       
  • African fermented foods and probiotics
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Charles M.A.P. Franz , Melanie Huch , Julius Maina Mathara , Hikmate Abriouel , Nabil Benomar , Gregor Reid , Antonio Galvez , Wilhelm H. Holzapfel
      Africa has an age old history of production of traditional fermented foods and is perhaps the continent with the richest variety of lactic acid fermented foods. These foods have a large impact on the nutrition, health and socio-economy of the people of the continent, often plagued by war, drought, famine and disease. Sub-Saharan Africa is the world's region with the highest percentage of chronically malnourished people and high child mortality. Further developing of traditional fermented foods with added probiotic health features would be an important contribution towards reaching the UN Millennium Development Goals of eradication of poverty and hunger, reduction in child mortality rates and improvement of maternal health. Specific probiotic strains with documented health benefits are sparsely available in Africa and not affordable to the majority of the population. Furthermore, they are not used in food fermentations. If such probiotic products could be developed especially for household food preparation, such as cereal or milk foods, it could make a profound impact on the health and well-being of adults and children. Suitable strains need to be chosen and efforts are needed to produce strains to make products which will be available for clinical studies. This can gauge the impact of probiotics on consumers' nutrition and health, and increase the number of people who can benefit.


      PubDate: 2014-09-11T19:18:51Z
       
  • Multilocus variable-number of tandem repeat analysis (MLVA) for
           Clostridium tyrobutyricum strains isolated from cheese production
           environment
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Masaharu Nishihara , Hajime Takahashi , Tomoko Sudo , Daisuke Kyoi , Toshio Kawahara , Yoshihiro Ikeuchi , Takashi Fujita , Takashi Kuda , Bon Kimura , Shuichi Yanahira
      Clostridium tyrobutyricum is a gram-positive spore-forming anaerobe that is considered as the main causative agent for late blowing in cheese due to butyric acid fermentation. In this study, multilocus variable-number of tandem repeat (VNTR) analysis (MLVA) for C. tyrobutyricum was developed to identify the source of contamination by C. tyrobutyricum spores in the cheese production environment. For each contig constructed from the results of a whole genome draft sequence of C. tyrobutyricum JCM11008T based on next-generation sequencing, VNTR loci that were effective for typing were searched using the Tandem Repeat Finder program. Five VNTR loci were amplified by polymerase chain reaction (PCR) to determine their number of repeats by sequencing, and MLVA was conducted. 25 strains of C. tyrobutyricum isolated from the environment, raw milk, and silage were classified into 18 MLVA types (DI=0.963). Of the C. tyrobutyricum strains isolated from raw milk, natural cheese, and blown processed cheese, strains with identical MLVA type were detected, which suggested that these strains might have shifted from natural cheese to blown processed cheese. MLVA could be an effective tool for monitoring contamination of natural cheese with C. tyrobutyricum in the processed cheese production environment because of its high discriminability, thereby allowing the analyst to trace the source of contamination.


      PubDate: 2014-09-06T19:11:50Z
       
  • Editorial Board
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189




      PubDate: 2014-09-06T19:11:50Z
       
  • L. monocytogenes in a cheese processing facility: Learning from
           contamination scenarios over three years of sampling
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): I. Rückerl , M. Muhterem-Uyar , S. Muri-Klinger , K.-H. Wagner , M. Wagner , B. Stessl
      The aim of this study was to analyze the changing patterns of Listeria monocytogenes contamination in a cheese processing facility manufacturing a wide range of ready-to-eat products. Characterization of L. monocytogenes isolates included genotyping by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Disinfectant-susceptibility tests and the assessment of L. monocytogenes survival in fresh cheese were also conducted. During the sampling period between 2010 and 2013, a total of 1284 environmental samples were investigated. Overall occurrence rates of Listeria spp. and L. monocytogenes were 21.9% and 19.5%, respectively. Identical L. monocytogenes genotypes were found in the food processing environment (FPE), raw materials and in products. Interventions after the sampling events changed contamination scenarios substantially. The high diversity of globally, widely distributed L. monocytogenes genotypes was reduced by identifying the major sources of contamination. Although susceptible to a broad range of disinfectants and cleaners, one dominant L. monocytogenes sequence type (ST) 5 could not be eradicated from drains and floors. Significantly, intense humidity and steam could be observed in all rooms and water residues were visible on floors due to increased cleaning strategies. This could explain the high L. monocytogenes contamination of the FPE (drains, shoes and floors) throughout the study (15.8%). The outcome of a challenge experiment in fresh cheese showed that L. monocytogenes could survive after 14days of storage at insufficient cooling temperatures (8 and 16°C). All efforts to reduce L. monocytogenes environmental contamination eventually led to a transition from dynamic to stable contamination scenarios. Consequently, implementation of systematic environmental monitoring via in-house systems should either aim for total avoidance of FPE colonization, or emphasize a first reduction of L. monocytogenes to sites where contamination of the processed product is unlikely. Drying of surfaces after cleaning is highly recommended to facilitate the L. monocytogenes eradication.


      PubDate: 2014-09-01T18:44:46Z
       
  • Development of a rapid capture-cum-detection method for Escherichia coli
           O157 from apple juice comprising nano-immunomagnetic separation in tandem
           with surface enhanced Raman scattering
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Roya Najafi , Shubhasish Mukherjee , Jim Hudson Jr. , Anup Sharma , Pratik Banerjee
      A combined capture and detection method comprising of nano-immunomagnetic separation (NIMS) and surface enhanced Raman spectroscopy (SERS) was developed to detect Escherichia coli O157 from liquid media including apple juice. The capture antibodies (cAbs) were immobilized on magnetite–gold (Fe3O4/Au) magnetic nanoparticles (MNPs) which were used for separation and concentration of the E. coli O157 cells from model liquid food matrix. The capture efficiency (CE) for E. coli O157 using MNP was found to be approximately 84–94%. No cross reactivity was observed with background non-target organisms. There was a significant difference in the mean CE of bacteria captured by MNP and commercially sourced immunomagnetic microbeads (p<0.05). For the detection of target pathogen, SERS labels were prepared by conjugating gold nanoparticles with Raman reporter molecules and the detector antibody (dAb). Au-Raman label-dAb was interacted with gold coated MNP-cAb-E. coli O157 complex. The ability of this immunoassay to detect E. coli O157 in apple juice was investigated. We have successfully applied the synthesized Fe3O4/Au nanoclusters to E. coli O157 detection in apple juice using the SERS method. The lowest detectable bacterial cell concentration in apple juice was 102 CFU/mL with a total analysis time of less than an hour. This method presents a convenient way of preconcentration, separation, and detection of low levels of target pathogen from liquid food matrix.


      PubDate: 2014-09-01T18:44:46Z
       
  • Genetic approaches to chemotype determination in type B-trichothecene
           producing Fusaria
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Matias Pasquali , Quirico Migheli
      This review summarises the genetic methods used for chemotype determination of the main Fusarium type B-trichothecene producing species. Literature on Fusarium chemotype epidemiology over the last 15 years is reviewed in order to describe temporal and spatial chemotype distribution of these fungi worldwide. Genetic approaches used for chemotype determination are also reviewed and discussed, highlighting successes and potential pitfalls of the technique. Results from both genetic and chemical approaches are summarised to compare reliability, advantages and limitations of the two methods. Potential applications of genetic chemotyping to toxigenic Fusarium species are evaluated in the light of improving food safety of agricultural products. The use of chemotype determination in population studies, toxin prediction as well as for breeding purpose is described.


      PubDate: 2014-09-01T18:44:46Z
       
  • Effect of sporulation medium on wet-heat resistance and structure of
           Alicyclobacillus acidoterrestris DSM 3922-type strain spores and modeling
           of the inactivation kinetics in apple juice
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Celenk Molva , Ayse Handan Baysal
      Alicyclobacillus acidoterrestris is a spoilage bacterium in fruit juices leading to high economic losses. The present study evaluated the effect of sporulation medium on the thermal inactivation kinetics of A. acidoterrestris DSM 3922 spores in apple juice (pH3.82±0.01; 11.3±0.1 °Brix). Bacillus acidocaldarius agar (BAA), Bacillus acidoterrestris agar (BATA), malt extract agar (MEA), potato dextrose agar (PDA) and B. acidoterrestris broth (BATB) were used for sporulation. Inactivation kinetic parameters at 85, 87.5 and 90°C were obtained using the log-linear model. The decimal reduction times at 85°C (D 85°C) were 41.7, 57.6, 76.8, 76.8 and 67.2min; D 87.5°C-values were 22.4, 26.7, 32.9, 31.5, and 32.9min; and D 90°C-values were 11.6, 9.9, 14.7, 11.9 and 14.1min for spores produced on PDA, MEA, BATA, BAA and BATB, respectively. The estimated z-values were 9.05, 6.60, 6.96, 6.15, and 7.46, respectively. The present study suggests that the sporulation medium affects the wet-heat resistance of A. acidoterrestris DSM 3922 spores. Also, the dipicolinic acid content (DPA) was found highest in heat resistant spores formed on mineral containing media. After wet-heat treatment, loss of internal volume due to the release of DPA from spore core was observed by scanning electron microscopy. Since, there is no standardized media for the sporulation of A. acidoterrestris, the results obtained from this study might be useful to determine and compare the thermal resistance characteristics of A. acidoterrestris spores in fruit juices.


      PubDate: 2014-09-01T18:44:46Z
       
  • Phytic acid degrading lactic acid bacteria in tef-injera fermentation
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Maren M. Fischer , Ines M. Egli , Isabelle Aeberli , Richard F. Hurrell , Leo Meile
      Ethiopian injera, a soft pancake, baked from fermented batter, is preferentially prepared from tef (Eragrostis tef) flour. The phytic acid (PA) content of tef is high and is only partly degraded during the fermentation step. PA chelates with iron and zinc in the human digestive tract and strongly inhibits their absorption. With the aim to formulate a starter culture that would substantially degrade PA during injera preparation, we assessed the potential of microorganisms isolated from Ethiopian household-tef fermentations to degrade PA. Lactic acid bacteria (LAB) were found to be among the dominating microorganisms. Seventy-six isolates from thirteen different tef fermentations were analyzed for phytase activity and thirteen different isolates of seven different species were detected to be positive in a phytase screening assay. In 20-mL model tef fermentations, out of these thirteen isolates, the use of Lactobacillus (L.) buchneri strain MF58 and Pediococcus pentosaceus strain MF35 resulted in lowest PA contents in the fermented tef of 41% and 42%, respectively of its initial content. In comparison 59% of PA remained when spontaneously fermented. Full scale tef fermentation (0.6L) and injera production using L. buchneri MF58 as culture additive decreased PA in cooked injera from 1.05 to 0.34±0.02g/100g, representing a degradation of 68% compared to 42% in injera from non-inoculated traditional fermentation. The visual appearance of the pancakes was similar. The final molar ratios of PA to iron of 4 and to zinc of 12 achieved with L. buchneri MF58 were decreased by ca. 50% compared to the traditional fermentation. In conclusion, selected LAB strains in tef fermentations can degrade PA, with L. buchneri MF58 displaying the highest PA degrading potential. The 68% PA degradation achieved by the application of L. buchneri MF58 would be expected to improve human zinc absorption from tef-injera, but further PA degradation is probably necessary if iron absorption has to be increased.


      PubDate: 2014-09-01T18:44:46Z
       
  • An educationally inspired illustration of two-dimensional Quantitative
           Microbiological Risk Assessment (QMRA) and sensitivity analysis
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): G.A. Vásquez , P. Busschaert , L.U. Haberbeck , M. Uyttendaele , A.H. Geeraerd
      Quantitative Microbiological Risk Assessment (QMRA) is a structured methodology used to assess the risk involved by ingestion of a pathogen. It applies mathematical models combined with an accurate exploitation of data sets, represented by distributions and – in the case of two-dimensional Monte Carlo simulations – their hyperparameters. This research aims to highlight background information, assumptions and truncations of a two-dimensional QMRA and advanced sensitivity analysis. We believe that such a detailed listing is not always clearly presented in actual risk assessment studies, while it is essential to ensure reliable and realistic simulations and interpretations. As a case-study, we are considering the occurrence of listeriosis in smoked fish products in Belgium during the period 2008–2009, using two-dimensional Monte Carlo and two sensitivity analysis methods (Spearman correlation and Sobol sensitivity indices) to estimate the most relevant factors of the final risk estimate. A risk estimate of 0.018% per consumption of contaminated smoked fish by an immunocompromised person was obtained. The final estimate of listeriosis cases (23) is within the actual reported result obtained for the same period and for the same population. Variability on the final risk estimate is determined by the variability regarding (i) consumer refrigerator temperatures, (ii) the reference growth rate of L. monocytogenes, (iii) the minimum growth temperature of L. monocytogenes and (iv) consumer portion size. Variability regarding the initial contamination level of L. monocytogenes tends to appear as a determinant of risk variability only when the minimum growth temperature is not included in the sensitivity analysis; when it is included the impact regarding the variability on the initial contamination level of L. monocytogenes is disappearing. Uncertainty determinants of the final risk indicated the need of gathering more information on the reference growth rate and the minimum growth temperature of L. monocytogenes. Uncertainty in the dose–response relationship was not included in the analysis, hence the level of its influence cannot be assessed in the present research. Finally, a baseline global workflow for QMRA and sensitivity analysis is proposed.


      PubDate: 2014-09-01T18:44:46Z
       
  • Microbial communities in air and wine of a winery at two consecutive
           vintages
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Fátima Pérez-Martín , Susana Seseña , Mónica Fernández-González , María Arévalo , María Llanos Palop
      The aim of this study was to assess, both quantitatively and qualitatively, the populations of lactic acid bacteria (LAB) and yeasts in air and wine of a winery, in order to evaluate the possible exchange of microorganisms between them. Samples were taken in a winery located in Castilla-La Mancha (Spain) during the winemaking period of two consecutive vintages (2011 and 2012). The microbial composition was determined by using both a culture-dependent method and a culture-independent method, PCR-denaturing gradient gel electrophoresis (PCR-DGGE). In addition, genetic characterization of isolates from plates was carried out. A high diversity of species was detected in air and wine samples from both vintages. Leuconostoc mesenteroides was the predominant lactic acid bacteria in air from both vintages while Oenococcus oeni was the predominant in wine. Saccharomyces cerevisiae was the most frequently isolated yeast in both air and wine. Typing of O. oeni and S. cerevisiae isolates from air and wine samples showed the presence of coincident genotypes in both samples, that would confirm the exchange of microorganisms between the two environments, air and wine, and furthermore some of these genotypes were also found at samples taken at different vintages, indicating that they would remain in the winery. The results display the influence of the activity taking place in the winery and the moment of fermentation of the wines in tanks, on the microorganisms present in the air and the role of the air for the dispersal of microorganisms within the winery.


      PubDate: 2014-09-01T18:44:46Z
       
  • Bovicin HC5 and nisin reduce Staphylococcus aureus adhesion to polystyrene
           and change the hydrophobicity profile and Gibbs free energy of adhesion
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Natan de Jesus Pimentel-Filho , Mayra Carla de Freitas Martins , Guilherme Bicalho Nogueira , Hilário Cuquetto Mantovani , Maria Cristina Dantas Vanetti
      Staphylococcus aureus is an opportunistic pathogen often multidrug-resistant that not only causes a variety of human diseases, but also is able to survive on biotic and abiotic surfaces through biofilm communities. The best way to inhibit biofilm establishment is to prevent cell adhesion. In the present study, subinhibitory concentrations of the bacteriocins bovicin HC5 and nisin were tested for their capability to interfere with the adhesion of S. aureus to polystyrene. Subinhibitory dosages of the bacteriocins reduced cell adhesion and this occurred probably due to changes in the hydrophobicity of the bacterial cell and polystyrene surfaces. After treatment with bovicin HC5 and nisin, the surfaces became more hydrophilic and the free energy of adhesion (∆G adhesion) between bacteria and the polystyrene surface was unfavorable. The transcriptional level of selected genes was assessed by RT-qPCR approach, revealing that the bacteriocins affected the expression of some important biofilm associated genes (icaD, fnbA, and clfB) and rnaIII, which is involved in the quorum sensing mechanism. The conditioning of food-contact surfaces with bacteriocins can be an innovative and powerful strategy to prevent biofilms in the food industry. The results are relevant for food safety as they indicate that bovicin HC5 and nisin can inhibit bacterial adhesion and consequent biofilm establishment, since cell adhesion precedes biofilm formation.


      PubDate: 2014-09-01T18:44:46Z
       
  • Benzalkonium chloride and heavy-metal tolerance in Listeria monocytogenes
           from retail foods
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Dongyang Xu , Yanli Li , M. Shamim Hasan Zahid , Shinji Yamasaki , Lei Shi , Jian-rong Li , He Yan
      Phenotypic and genotypic tolerance in 71 Listeria monocytogenes isolates from different varieties of foods to benzalkonium chloride (BC) and cadmium were investigated by susceptibility test and molecular methods. To investigate the role of efflux pumps in BC tolerance, reserpine, an efflux pump inhibitor, was added to the BC tolerant strains. Tolerance to BC and cadmium were 26.8% (19/71) and 49.3% (35/71) respectively. Strains with BC tolerance were significantly more frequent among those of serotype 4b (100%, 6/6) than among those of serotype 1/2a (or 3a) (13.5%, 5/37), which represent the predominant number of strains (52.1%, 37/71). Tolerance to cadmium was encountered among 62.2% (23/37) and 50.0% (3/6) of the serotype 1/2a (or 3a) and 4b strains, respectively, and among 19.0% (4/21) of the strains of the serotype 1/2c. All of the 10 (14.1%) isolates found to be BC and cadmium co-tolerance were isolated from raw meat or quick-frozen food made of wheat flour and rice. Five multi-drug resistant strains were tolerant to cadmium as well. Among 71 isolates examined, one contained qacA and three contained qacEΔ1-sul. To the best of our knowledge, this is the first detection of qacA and qacEΔ1-sul in L. monocytogenes, an indication of the possible horizontal transfer of the two genes. Addition of reserpine to the tolerant strains resulted in the loss of tolerance among seven out of 19 BC strains, suggesting a certain role the efflux pump played in mediating BC tolerance. Of the three distinct cadA types known to date in L. monocytogenes, the cadA1 and cadA2 genes were detected among 24 (33.8%) and three (4.2%) isolates respectively. The presence of cadA1 and cadA2 largely corresponded to the susceptibility phenotype. A subset (9/35 [25.7%]) of the cadmium-tolerant isolates lacked the known cadmium resistance determinants. These findings suggest that food products could act as a reservoir for L. monocytogenes harboring tolerance to BC and cadmium and will further our understanding of the adaptations of this organism to these two compounds.


      PubDate: 2014-09-01T18:44:46Z
       
  • Control of tyramine and histamine accumulation by lactic acid bacteria
           using bacteriocin forming lactococci
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Giulia Tabanelli , Chiara Montanari , Eleonora Bargossi , Rosalba Lanciotti , Veronica Gatto , Giovanna Felis , Sandra Torriani , Fausto Gardini
      The aim of this study was to evaluate the competitive effects of three bacteriocin producing strains of Lactococcus lactis subsp. lactis against two aminobiogenic lactic acid bacteria, i.e. the tyramine producing strain Enterococcus faecalis EF37 and the histamine producing strain Streptococcus thermophilus PRI60, inoculated at different initial concentrations (from 2 to 6logcfu/ml). The results showed that the three L. lactis subsp. lactis strains were able to produce bacteriocins: in particular, L. lactis subsp. lactis VR84 and EG46 produced, respectively, nisin Z and lacticin 481, while for the strains CG27 the bacteriocin has not been yet identified, even if its peptidic nature has been demonstrated. The co-culture of E. faecalis EF37 in combination with lactococci significantly reduced the growth potential of this aminobiogenic strain, both in terms of growth rate and maximum cell concentration, depending on the initial inoculum level of E. faecalis. Tyramine accumulation was strongly reduced when E. faecalis EF37 was inoculated at 2logcfu/ml and, to a lesser extent, at 3logcfu/ml, as a result of a lower cell load of the aminobiogenic strain. All the lactococci were more efficient in inhibiting streptococci in comparison with E. faecalis EF37; in particular, L. lactis subsp. lactis VR84 induced the death of S. thermophilus PRI60 and allowed the detection of histamine traces only at higher streptococci inoculum levels (5–6logcfu/ml). The other two lactococcal strains did not show a lethal action against S. thermophilus PRI60, but were able to reduce its growth extent and histamine accumulation, even if L. lactis subsp. lactis EG46 was less effective when the initial streptococci concentration was 5 and 6logcfu/ml. This preliminary study has clarified some aspects regarding the ratio between bacteriocinogenic strains and aminobiogenic strains with respect to the possibility to accumulate BA and has also showed that different bacteriocins can have different effects on BA production on the same strain. This knowledge is essentially aimed to use bacteriocinogenic lactococci as a predictable strategy against aminobiogenic bacteria present in cheese or other fermented foods.


      PubDate: 2014-09-01T18:44:46Z
       
  • Removal of Salmonella enterica Enteritidis and Escherichia coli from green
           peppers and melons by ultrasound and organic acids
    • Abstract: Publication date: 3 November 2014
      Source:International Journal of Food Microbiology, Volume 190
      Author(s): Jackline Freitas Brilhante de São José , Hiasmyne Silva de Medeiros , Patrícia Campos Bernardes , Nélio José de Andrade
      The aim of this study was to evaluate the effectiveness of ultrasound treatment combined with organic acids in the decontamination step for green peppers and melons. The influence of the surface roughness of the peppers and melons on bacterial adhesion was evaluated, as measured using a profilometer. The adhesion of Salmonella enterica serovar Enteritidis and Escherichia coli to the green pepper and melon surfaces was also evaluated by measuring the hydrophobicity of the microorganisms and the surfaces. The bacteria that adhered to the surface of green peppers and melons was quantified by plate count and visualized by scanning electron microscopy. In addition, the efficiency of ultrasound and organic acids to remove bacteria from the pepper and melon surfaces was examined. The average roughness (R a) of the green peppers (13.0±2.7nm) was significantly different (p >0.05) from the melons (33.5±7.9nm). Adherence of S. Enteritidis and E. coli are thermodynamically unfavorable for both surfaces studied (∆G adhesion >0). Despite these data, good adhesion occurred on both surfaces. The number of bacteria on green pepper slices was 7.3 and 7.0logCFU/cm2 for E. coli and S. enterica Enteritidis, respectively. For melon surfaces, the number of bacteria was 7.0 and 6.9logCFU/cm2 for E. coli and S. Enteritidis, respectively. The greater adherence of both bacteria on the green peppers can be explained by its hydrophobic surface; the hydrophilic surfaces of melons resulted in lower adherence. These results suggest that the adhesion observed in this experiment is a multifactorial process. Among the treatments evaluated for green peppers, a higher removal of pathogens was observed after use of a combination of ultrasound and 1% lactic acid; this treatment reduced E. coli and Salmonella by 2.9 and 2.8logCFU/cm2, respectively. For melons, the combination of ultrasound and lactic acid showed a reduction of 2.5 and 3.1logCFU/cm2 for E. coli and S. Enteritidis, respectively. These results indicate that it is possible to replace the chlorinated compounds that are commonly used to sanitize fruits and vegetables. These results confirm that ultrasound, an emerging technology for food processing applications, could enhance the microbial safety of fresh produce.


      PubDate: 2014-09-01T18:44:46Z
       
  • Shedding of Salmonella in single age caged commercial layer flock at an
           early stage of lay
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Vaibhav C. Gole , Charles G.B. Caraguel , Margaret Sexton , Chelsea Fowler , Kapil K. Chousalkar
      The shedding of Salmonella in a single age commercial egg layer flock was investigated at the onset of lay (18weeks) followed by two longitudinal samplings at 24 and 30weeks. At the age of 18weeks, when the first sampling was performed, the prevalence of Salmonella in faeces was 82.14% whereas all egg belt and dust samples were Salmonella positive by culture method. In later samplings, at the age of 24 and 30weeks, the prevalence of Salmonella in faeces was significantly reduced (p<0.001) to 38.88% and 12.95% respectively, however all egg belt and dust samples remained positive by culture method. The prevalence of Salmonella in faeces collected from the low tier cages was significantly higher (p=0.009) as compared with samples from the high tier cages. In all types of samples processed by culture method, S. Mbandaka was the most frequently (54.40%) isolated serovar followed by S. Worthington (37.60%), S. Anatum (0.8%), and S. Infantis (0.8%). All samples were also tested by real-time PCR method. The observed agreement between culture method and real-time PCR in detecting Salmonella-positive dust and egg belt samples was 100%. There was almost perfect agreement (observed agreement=99.21%) for the detection of Salmonella-positive eggshells. Observed agreement between culture method and real-time PCR for detecting Salmonella-positive shoe cover and faecal samples was, however, moderate (80%) and low (54.27%) respectively. Real-time PCR results showed that there was a significant increase in the load of Salmonella on egg belt, dust and shoe cover samples at the 24 and 30weeks of lay as compared to the 18weeks of lay. Real-time PCR provided a more rapid and reliable method of detection of Salmonella on all dry sample types whereas the traditional culture method proved much more reliable when trying to detect Salmonella in wet faecal samples.


      PubDate: 2014-08-15T17:50:30Z
       
  • Occurrence of the three major Vibrio species pathogenic for human in
           seafood products consumed in France using real-time PCR
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Annick Robert-Pillot , Stéphanie Copin , Charlotte Himber , Mélanie Gay , Marie-Laure Quilici
      Vibrio spp. have emerged as a serious threat to human health worldwide. Vibrio parahaemolyticus, Vibrio cholerae and Vibrio vulnificus are of particular concern as they have been linked to gastrointestinal infections and septicemia associated with the consumption of raw or undercooked seafood. We developed hydrolysis probe-based real-time PCR systems with an internal amplification control for the detection of these species. We applied these systems to a total of 167 fresh or frozen crustacean, fish and shellfish samples consumed in France. Of them, 34.7% (n =58) were positive for Vibrio. V. parahaemolyticus was the most common, in 31.1% of samples, followed by V. vulnificus in 12.6% and V. cholerae in 0.6%. Furthermore, V. parahaemolyticus and V. vulnificus were present simultaneously in 9.6% of samples. Virulence genes (tdh and trh sequences) were present in 25% of the V. parahaemolyticus-positive samples. The V. cholerae strain detected was non toxigenic. The densities of V. parahaemolyticus and V. cholerae ranged from <102 to 104 bacteria/g of seafood. All samples positive for V. vulnificus displayed low-level contamination with fewer than 102 bacteria/g. Our findings indicate that seafood consumption presents a potential risk to human health in France and highlight the importance of tools for a preventive consumer protection policy.


      PubDate: 2014-08-15T17:50:30Z
       
  • Development of a selective agar plate for the detection of Campylobacter
           spp. in fresh produce
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Jin-Hee Yoo , Na-Young Choi , Young-Min Bae , Jung-Su Lee , Sun-Young Lee
      This study was conducted to develop a selective medium for the detection of Campylobacter spp. in fresh produce. Campylobacter spp. (n=4), non-Campylobacter (showing positive results on Campylobacter selective agar) strains (n=49) isolated from fresh produce, indicator bacteria (n=13), and spoilage bacteria isolated from fresh produce (n=15) were plated on four Campylobacter selective media. Bolton agar and modified charcoal cefoperazone deoxycholate agar (mCCDA) exhibited higher sensitivity for Campylobacter spp. than did Preston agar and Hunt agar, although certain non-Campylobacter strains isolated from fresh produce by using a selective agar isolation method, were still able to grow on Bolton agar and mCCDA. To inhibit the growth of non-Campylobacter strains, Bolton agar and mCCDA were supplemented with 5 antibiotics (rifampicin, polymyxin B, sodium metabisulfite, sodium pyruvate, ferrous sulfate) and the growth of Campylobacter spp. (n=7) and non-Campylobacter strains (n=44) was evaluated. Although Bolton agar supplemented with rifampicin (BR agar) exhibited a higher selectivity for Campylobacter spp. than did mCCDA supplemented with antibiotics, certain non-Campylobacter strains were still able to grow on BR agar (18.8%). When BR agar with various concentrations of sulfamethoxazole–trimethoprim were tested with Campylobacter spp. (n=8) and non-Campylobacter (n=7), sulfamethoxazole–trimethoprim was inhibitory against 3 of 7 non-Campylobacter strains. Finally, we validated the use of BR agar containing 50mg/L sulfamethoxazole (BRS agar) or 0.5mg/L ciprofloxacin (BRCS agar) and other selective agars for the detection of Campylobacter spp. in chicken and fresh produce. All chicken samples were positive for Campylobacter spp. when tested on mCCDA, BR agar, and BRS agar. In fresh produce samples, BRS agar exhibited the highest selectivity for Campylobacter spp., demonstrating its suitability for the detection of Campylobacter spp. in fresh produce.


      PubDate: 2014-08-15T17:50:30Z
       
  • Biocontrol activity of four non- and low-fermenting yeast strains against
           Aspergillus carbonarius and their ability to remove ochratoxin A from
           grape juice
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Stefano Fiori , Pietro Paolo Urgeghe , Walid Hammami , Salvatorico Razzu , Samir Jaoua , Quirico Migheli
      Aspergillus spp. infection of grape may lead to ochratoxin A (OTA) contamination in processed beverages such as wine and grape juice. The aim of the current study was to evaluate the biocontrol potential of two non-fermenting (Cyberlindnera jadinii 273 and Candida friedrichii 778) and two low-fermenting (Candida intermedia 235 and Lachancea thermotolerans 751) yeast strains against the pathogenic fungus and OTA-producer Aspergillus carbonarius, and their ability to remove OTA from grape juice. Two strains, 235 and 751, showed a significant ability to inhibit A. carbonarius both on grape berries and in in vitro experiments. Neither their filtrate nor their autoclaved filtrate culture broth was able to prevent consistently pathogen growth. Volatile organic compounds (VOCs) produced by all four selected yeasts were likely able to consistently prevent pathogen sporulation in vitro. VOCs produced by the non-fermenting strain 778 also significantly reduced A. carbonarius vegetative growth. Three yeast strains (235, 751, and 778) efficiently adsorbed artificially spiked OTA from grape juice, while autoclaving treatment improved OTA adsorption capacity by all the four tested strains. Biological control of A. carbonarius and OTA-decontamination using yeast is proposed as an approach to meet the Islamic dietary laws concerning the absence of alcohol in halal beverages.


      PubDate: 2014-08-12T17:38:59Z
       
  • Distribution of aflatoxigenic Aspergillus section Flavi in commercial
           poultry feed in Nigeria
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): C.N. Ezekiel , J. Atehnkeng , A.C. Odebode , R. Bandyopadhyay
      The distribution and aflatoxigenicity of Aspergillus section Flavi isolates in 58 commercial poultry feed samples obtained from 17 states in five agro-ecological zones (AEZs) in Nigeria were determined in order to assess the safety of the feeds with respect to aflatoxin-producing fungi. Correlation was also performed for incidence of species, aflatoxin-producing ability of isolates in vitro, and aflatoxin (AFB1) concentrations in the feed. A total of 1006 Aspergillus section Flavi isolates were obtained from 87.9% of the feed samples and identified as Aspergillus flavus, unnamed taxon SBG, Aspergillus parasiticus and Aspergillus tamarii. A. flavus was the most prevalent (91.8%) of the isolates obtained from the feed in the AEZs while A. parasiticus had the lowest incidence (0.1%) and was isolated only from a layer mash sample collected from the DS zone. About 29% of the Aspergillus isolates produced aflatoxins in maize grains at concentrations up to 440,500μg/kg B and 341,000μg/kgG aflatoxins. The incidence of toxigenic isolates was highest (44.4%) in chick mash and lowest (19.9%) in grower mash. The population of A. flavus in the feed had positive (r =0.50) but non significant (p >0.05) correlations with proportion of toxigenic isolates obtained from the feed while SBG had significant (p <0.001) positive (r =0.99) influence on AFB1 concentrations in the feed. Poultry feed in Nigerian markets are therefore highly contaminated with aflatoxigenic Aspergillus species and consequently, aflatoxins. This is a potential threat to the poultry industry and requires urgent intervention.


      PubDate: 2014-08-12T17:38:59Z
       
  • Sequencing, physical organization and kinetic expression of the patulin
           biosynthetic gene cluster from Penicillium expansum
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Joanna Tannous , Rhoda El Khoury , Selma P. Snini , Yannick Lippi , André El Khoury , Ali Atoui , Roger Lteif , Isabelle P. Oswald , Olivier Puel
      Patulin is a polyketide-derived mycotoxin produced by numerous filamentous fungi. Among them, Penicillium expansum is by far the most problematic species. This fungus is a destructive phytopathogen capable of growing on fruit, provoking the blue mold decay of apples and producing significant amounts of patulin. The biosynthetic pathway of this mycotoxin is chemically well-characterized, but its genetic bases remain largely unknown with only few characterized genes in less economic relevant species. The present study consisted of the identification and positional organization of the patulin gene cluster in P. expansum strain NRRL 35695. Several amplification reactions were performed with degenerative primers that were designed based on sequences from the orthologous genes available in other species. An improved genome Walking approach was used in order to sequence the remaining adjacent genes of the cluster. RACE-PCR was also carried out from mRNAs to determine the start and stop codons of the coding sequences. The patulin gene cluster in P. expansum consists of 15 genes in the following order: patH, patG, patF, patE, patD, patC, patB, patA, patM, patN, patO, patL, patI, patJ, and patK. These genes share 60–70% of identity with orthologous genes grouped differently, within a putative patulin cluster described in a non-producing strain of Aspergillus clavatus. The kinetics of patulin cluster genes expression was studied under patulin-permissive conditions (natural apple-based medium) and patulin-restrictive conditions (Eagle's minimal essential medium), and demonstrated a significant association between gene expression and patulin production. In conclusion, the sequence of the patulin cluster in P. expansum constitutes a key step for a better understanding of the mechanisms leading to patulin production in this fungus. It will allow the role of each gene to be elucidated, and help to define strategies to reduce patulin production in apple-based products.


      PubDate: 2014-08-12T17:38:59Z
       
  • Characterization of integrons and resistance genes in multidrug-resistant
           Salmonella enterica isolated from meat and dairy products in Egypt
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Ashraf M. Ahmed , Toshi Shimamoto , Tadashi Shimamoto
      Foodborne pathogens are a leading cause of illness and death, especially in developing countries. The problem is exacerbated if bacteria attain multidrug resistance. Little is currently known about the extent of antibiotic resistance in foodborne pathogens and the molecular mechanisms underlying this resistance in Africa. Therefore, the current study was carried out to characterize, at the molecular level, the mechanism of multidrug resistance in Salmonella enterica isolated from 1600 food samples (800 meat products and 800 dairy products) collected from different street venders, butchers, retail markets and slaughterhouses in Egypt. Forty-seven out of 69 isolates (68.1%) showed multidrug resistance phenotypes to at least three classes of antimicrobials. The incidence of multidrug-resistant isolates was higher in meat products (37, 69.8%) than in dairy products (10, 62.5%). The multidrug-resistant serovars included, S. enterica serovar Typhimurium (24 isolates, 34.8%), S. enterica serovar Enteritidis, (15 isolates, 21.8%), S. enterica serovar Infantis (7 isolates, 10.1%) and S. enterica non-typable serovar (1 isolate, 1.4%). The highest resistance was to ampicillin (95.7%), then to kanamycin (93.6%), spectinomycin (93.6%), streptomycin (91.5%) and sulfamethoxazole/trimethoprim (91.5%). PCR and DNA sequencing were used to screen and characterize integrons and antibiotic resistance genes and 39.1% and 8.7% of isolates were positive for class 1 and class 2 integrons, respectively. β-lactamase-encoding genes were identified in 75.4% of isolates and plasmid-mediated quinolone resistance genes were identified in 27.5% of isolates. Finally, the florphenicol resistance gene, floR, was identified in 18.8% of isolates. PCR screening identified S. enterica serovar Typhimurium DT104 in both meat and dairy products. This is the first study to report many of these resistance genes in dairy products. This study highlights the high incidence of multidrug-resistant S. enterica in meat and dairy products in Egypt, with the possibility of their transfer to humans leading to therapeutic failure. Therefore, the overuse of antibiotics in animals should be drastically reduced in developing countries.


      PubDate: 2014-08-12T17:38:59Z
       
  • Characterization of an unusual Salmonella phage type DT7a and report of a
           foodborne outbreak of salmonellosis
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): A.A. Lettini , C. Saccardin , E. Ramon , A. Longo , E. Cortini , M.C. Dalla Pozza , L. Barco , B. Guerra , I. Luzzi , A. Ricci
      Salmonella enterica subsp. enterica serovar 4,[5],12,i:− is a monophasic variant of Salmonella Typhimurium and its occurrence has markedly increased in several European countries in the last ten years. In June 2011, an outbreak of Salmonella 4,[5],12,i:− was reported among attendees of a wedding reception in the North-East of Italy. The source of this outbreak was identified as a cooked pork product served during the wedding reception. All Salmonella isolates from humans and the contaminated pork products were identified as Salmonella 4,[5],12,i:− and phage typed as DT7a. Afterwards, the farm where the pigs were raised was identified and sampled, and Salmonella Typhimurium was isolated from swine fecal samples. Despite the difference in serovar, these Salmonella Typhimurium isolates were also phage typed as DT7a. In the present study, Salmonella isolates from animals, humans and pork products during the outbreak investigation were subtyped by pulsed-field gel electrophoresis (PFGE), Multiple-Locus Variable number tandem repeats Analysis (MLVA), and resistance patterns, aiming to identify the most suitable subtyping methods to characterize isolates associated with this outbreak. In addition, a collection of epidemiologically unrelated strains of Salmonella 4,[5],12,i:− and Salmonella Typhimurium sharing the same phage type (DT7a) was similarly characterized in order to investigate their genetic relationship. This study provides a first snapshot of a rare Salmonella phage type, DT7a, associated with both Salmonella 4,[5],12,i:− and Salmonella Typhimurium. Moreover, the study demonstrated that in this specific context MLVA could be a reliable tool to support outbreak investigations as well as to assess the genetic relatedness among Salmonella isolates.


      PubDate: 2014-08-12T17:38:59Z
       
  • Comparison of identification systems for psychrotrophic bacteria isolated
           from raw bovine milk
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): Nuwan R. Vithanage , Thomas R. Yeager , Snehal R. Jadhav , Enzo A. Palombo , Nivedita Datta
      Psychrotrophic bacteria in raw milk produce heat-resistant extracellular proteases, resulting in spoilage and shelf-life reduction of ultrahigh temperature treated milk and milk products. Controlling of these spoilage microbes requires rapid and reliable identification systems for screening of raw milk. This study aimed to compare commercial bacterial identification systems with a genetic method (considered as the ‘gold standard’ method) for the identification of heat-resistant protease producing bacteria in raw milk. Five bacterial identification systems were compared based on typability, discrimination power (i.e. Simpson's Index of Diversity), reproducibility and speed of analysis. The accuracy of 16S rRNA gene sequencing, Biolog, MALDI-TOF MS, API, and Microbact for the identification of Gram negative bacilli at the species level was 100.0%, 86.8%, 63.2%, 60.5% and 57.9%, respectively. The Gram positive bacilli were identified by 16S rRNA gene sequencing, Biolog, MALDI-TOF MS, and API with accuracies at the species level of 100.0%, 85.0%, 95.0% and 90.0%, respectively. The 16S rRNA gene sequencing and phylogenetic analysis discriminated Pseudomonas fluorescens, Pseudomonas syringae, Hafnia alvei, Bacillus cereus, Bacillus pumilus and Bacillus licheniformis to the subspecies level. The Simpson's Index of Diversity scores were 0.966, 0.711, 0.496, 0.472, and 0.140, for 16S rRNA gene sequencing, Biolog, MALDI-TOF MS, API and Microbact, respectively. Limited reference profiles in the databases of Biolog, MALDI-TOF MS, API and Microbact systems reduced their accuracy in bacterial identification, compared to 16S rRNA gene sequencing. The rapidity of each assay is in the following order; MALDI-TOF MS>16S rRNA gene sequencing>Biolog>Microbact>API. The reproducibility of the assays is in the order of 16S rRNA gene sequencing>API>Microbact>MALDI-TOF MS>Biolog. Thus, 16S rRNA gene sequencing appears to be the most reliable and robust system for the identification of dairy spoilage bacteria. The Biolog system is suitable for the identification of Gram negative spoilage bacteria, while MALDI-TOF MS and API systems are suitable for the identification of Gram positive spoilage bacteria isolated from raw milk. The commercial systems used in this study have been developed and extensively used for the identification of clinical microbes but only a limited number of studies used those systems to identify the environmental microorganisms that often contaminate raw milk. Therefore, comparison of those systems for the identification of spoilage microbes in raw milk would provide better understanding of their suitability for routine dairy microbiology and more extensive dairy research.


      PubDate: 2014-08-12T17:38:59Z
       
  • Buckwheat achenes antioxidant profile modulates Aspergillus flavus growth
           and aflatoxin production
    • Abstract: Publication date: 17 October 2014
      Source:International Journal of Food Microbiology, Volume 189
      Author(s): G. Chitarrini , C. Nobili , F. Pinzari , A. Antonini , P. De Rossi , A. Del Fiore , S. Procacci , V. Tolaini , V. Scala , M. Scarpari , M. Reverberi
      Buckwheat (Fagopyrum spp.) is a “pseudo-cereal” of great interest in the production of healthy foods since its flour, derived from achenes, is enriched with bioactive compounds and, due to the absence of gluten, may be used in composition of celiac diets. Amongst buckwheat species, F. tataricum achenes possess a larger amount of the antioxidant flavenol rutin than the common buckwheat F. esculentum. Ongoing climate change may favor plant susceptibility to the attack by pathogenic, often mycotoxigenic, fungi with consequent increase of mycotoxins in previously unexploited feeds and foodstuffs. In particular, Aspergillus flavus, under suitable environmental conditions such as those currently occurring in Italy, may produce aflatoxin B1 (AFB1), the most carcinogenic compound of fungal origin which is classified by IARC as Category 1. In this study, the viable achenes of two buckwheat species, F. tataricum (var. Golden) and F. esculentum (var. Aelita) were inoculated with an AFB1-producing A. flavus NRRL 3357 to analyze their relative performances against fungal invasion and toxin contamination. Notably, we sought the existence of a correlation between the amount of tocols/flavonols in the achenes of buckwheat, infected and non-infected with A. flavus, and to analyze the ability of the pathogen to grow and produce toxin during achene infection. Results suggest that achenes of F. tataricum, the best producer of antioxidant compounds in this study, are less susceptible to A. flavus infection and consequently, but not proportionally, to mycotoxin contamination compared with F. esculentum. Moreover, rutin-derived quercetin appears to be more efficient in inhibiting aflatoxin biosynthesis than the parent compound.


      PubDate: 2014-08-12T17:38:59Z
       
 
 
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