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  Subjects -> BIOLOGY (Total: 2834 journals)
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MICROBIOLOGY (240 journals)                  1 2 3     

Acta Microbiologica et Immunologica Hungarica     Full-text available via subscription   (Followers: 5)
Addiction Genetics     Open Access   (Followers: 5)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 18)
Advances in Microbiology     Open Access   (Followers: 17)
Advances in Molecular Imaging     Open Access   (Followers: 2)
African Journal of Clinical and Experimental Microbiology     Open Access   (Followers: 1)
African Journal of Microbiology Research     Open Access   (Followers: 1)
Algorithms for Molecular Biology     Open Access   (Followers: 4)
American Journal of Infectious Diseases and Microbiology     Open Access   (Followers: 15)
American Journal of Microbiological Research     Open Access  
American Journal of Microbiology     Open Access   (Followers: 15)
American Journal of Molecular Biology     Open Access   (Followers: 2)
American Journal of Stem Cell Research     Open Access   (Followers: 1)
Annals of Clinical Microbiology and Antimicrobials     Open Access   (Followers: 6)
Annals of Microbiology     Hybrid Journal   (Followers: 9)
Annual Review of Microbiology     Full-text available via subscription   (Followers: 25)
Antimicrobial Agents and Chemotherapy     Full-text available via subscription   (Followers: 16)
Applied and Environmental Microbiology     Full-text available via subscription   (Followers: 34)
Applied Biochemistry and Microbiology     Hybrid Journal   (Followers: 8)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 30)
Archives of Microbiology     Hybrid Journal   (Followers: 4)
Avicenna Journal of Clinical Microbiology and Infection     Open Access  
Bangladesh Journal of Medical Microbiology     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  
Bioethanol     Open Access  
Biomaterials Science     Full-text available via subscription   (Followers: 4)
BioMolecular Concepts     Hybrid Journal   (Followers: 2)
Biomolecular Detection and Quantification     Open Access  
Biomolecules     Open Access   (Followers: 1)
BMC Microbiology     Open Access   (Followers: 8)
Brazilian Journal of Microbiology     Open Access   (Followers: 2)
Canadian Journal of Infectious Diseases & Medical Microbiology     Hybrid Journal   (Followers: 2)
Canadian Journal of Microbiology     Full-text available via subscription   (Followers: 3)
Cell Biology : Research & Therapy     Hybrid Journal   (Followers: 1)
Cell Host & Microbe     Full-text available via subscription   (Followers: 10)
Cell Medicine     Open Access   (Followers: 1)
Cell Regeneration     Open Access  
Cell Stem Cell     Full-text available via subscription   (Followers: 23)
CellBio     Open Access  
Cells     Open Access   (Followers: 1)
Cellular & Molecular Immunology     Hybrid Journal   (Followers: 9)
Cellular and Molecular Biology Letters     Open Access   (Followers: 1)
Cellular Microbiology     Hybrid Journal   (Followers: 5)
Cellular Senescence and Therapy     Open Access  
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: 16)
Clinical Microbiology Newsletter     Hybrid Journal   (Followers: 4)
Clinical Microbiology Reviews     Full-text available via subscription   (Followers: 10)
Comparative Immunology, Microbiology and Infectious Diseases     Hybrid Journal   (Followers: 9)
Computational Molecular Bioscience     Open Access   (Followers: 1)
Critical Reviews in Microbiology     Hybrid Journal   (Followers: 8)
Current Clinical Microbiology Reports     Hybrid Journal  
Current Issues in Molecular Biology     Open Access   (Followers: 1)
Current Microbiology     Hybrid Journal   (Followers: 6)
Current Molecular Biology Reports     Hybrid Journal  
Current Molecular Imaging     Hybrid Journal  
Current Opinion in Microbiology     Hybrid Journal   (Followers: 19)
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: 6)
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: 14)
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: 11)
European Journal of Microbiology and Immunology     Open Access   (Followers: 9)
Experimental and Molecular Pathology     Hybrid Journal   (Followers: 5)
Fems Microbiology Ecology     Hybrid Journal   (Followers: 6)
Fems Microbiology Letters     Hybrid Journal   (Followers: 15)
Fems Microbiology Reviews     Hybrid Journal   (Followers: 19)
Fermentation     Open Access  
Folia Histochemica et Cytobiologica     Open Access  
Folia Microbiologica     Hybrid Journal   (Followers: 1)
Food Microbiology     Hybrid Journal   (Followers: 13)
Frontiers in Cell and Developmental Biology     Open Access   (Followers: 2)
Frontiers in Cellular and Infection Microbiology     Open Access   (Followers: 2)
Frontiers in Cellular Neuroscience     Open Access   (Followers: 2)
Frontiers in Microbiology     Open Access   (Followers: 6)
Frontiers in Molecular Neuroscience     Open Access   (Followers: 1)
Future Microbiology     Full-text available via subscription   (Followers: 2)
Future Virology     Full-text available via subscription   (Followers: 7)
Gene Expression     Full-text available via subscription  
Genetica si Biologie Moleculara     Open Access  
Genetics and Molecular Research     Open Access   (Followers: 4)
Geomicrobiology Journal     Hybrid Journal   (Followers: 1)
Gut Microbes     Full-text available via subscription   (Followers: 4)
IAWA Journal     Hybrid Journal  
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)
Inside the Cell     Open Access  
International Journal of Antimicrobial Agents     Hybrid Journal   (Followers: 4)

        1 2 3     

Journal Cover   International Journal of Food Microbiology
  [SJR: 1.614]   [H-I: 121]   [13 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0168-1605
   Published by Elsevier Homepage  [2800 journals]
  • Editorial Board
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211




      PubDate: 2015-08-16T14:10:07Z
       
  • ICFMH Announcement
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211




      PubDate: 2015-08-16T14:10:07Z
       
  • Inactivation of Byssochlamys nivea ascospores in strawberry puree by high
           pressure, power ultrasound and thermal processing
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Evelyn, F.V.M. Silva
      Byssochlamys nivea is a mold that can spoil processed fruit products and produce mycotoxins. In this work, high pressure processing (HPP, 600MPa) and power ultrasound (24kHz, 0.33W/mL; TS) in combination with 75°C for the inactivation of four week old B. nivea ascospores in strawberry puree for up to 30min was investigated and compared with 75°C thermal processing alone. TS and thermal processing can activate the mold ascospores, but HPP–75°C resulted in 2.0 log reductions after a 20min process. For a 10min process, HPP–75°C was better than 85°C alone in reducing B. nivea spores (1.4 vs. 0.2 log reduction), demonstrating that a lower temperature in combination with HPP is more effective for spore inactivation than heat alone at a higher temperature. The ascospore inactivation by HPP–thermal, TS and thermal processing was studied at different temperatures and modeled. Faster inactivation was achieved at higher temperatures for all the technologies tested, indicating the significant role of temperature in spore inactivation, alone or combined with other physical processes. The Weibull model described the spore inactivation by 600MPa HPP–thermal (38, 50, 60, 75°C) and thermal (85, 90°C) processing, whereas the Lorentzian model was more appropriate for TS treatment (65, 70, 75°C). The models obtained provide a useful tool to design and predict pasteurization processes targeting B. nivea ascospores.


      PubDate: 2015-08-16T14:10:07Z
       
  • 2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) inhibits
           trichothecene production by Fusarium graminearum through suppression of
           Tri6 expression
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Thomas Etzerodt, Kazuyuki Maeda, Yuichi Nakajima, Bente Laursen, Inge S. Fomsgaard, Makoto Kimura
      Fusarium head blight (FHB) is a devastating disease of wheat (Triticum aestivum L.) caused by a mycotoxigenic fungus Fusarium graminearum resulting in significantly decreased yields and accumulation of toxic trichothecenes in grains. We tested 7 major secondary metabolites from wheat for their effect on trichothecene production in liquid cultures of F. graminearum producing trichothecene 15-acetyldeoxynivalenol (15-ADON). 2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) benzoxazinoid completely abolished toxin production without any apparent effect on fungal growth. DIMBOA strongly affected the expression of Tri6, encoding a major transcriptional regulator of several genes of the trichothecene biosynthesis pathway. DIMBOA also repressed expression of Tri5, encoding trichodiene synthase, the first enzyme in the trichothecene biosynthesis pathway. Thus, DIMBOA could play an important role against the accumulation of trichothecenes in wheat grain. Breeding or engineering of wheat with increased levels of benzoxazinoids could provide varieties with increased resistance against trichothecene contamination of grain and lower susceptibility to FHB.


      PubDate: 2015-08-16T14:10:07Z
       
  • Evaluation of different buffered peptone water (BPW) based enrichment
           broths for detection of Gram-negative foodborne pathogens from various
           food matrices
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): H. Margot, M.H. Zwietering, H. Joosten, Emer O'Mahony, R. Stephan
      This study evaluated the effects of changing the composition of the pre-enrichment medium buffered peptone water (BPW) on the growth of stressed and unstressed Gram-negative foodborne pathogens in a one-broth enrichment strategy. BPW supplemented with an available iron source and sodium pyruvate, along with low levels of 8-hydroxyquinoline and sodium deoxycholate (BPW-S) improved the recovery of desiccated Cronobacter spp. from powdered infant formula. Growth of Salmonella and STEC was comparable in all BPW variants tested for different food matrices. In products with high levels of Gram-negative background flora (e.g. sprouts), the target organisms could not be reliably detected by PCR in any of the BPW variants tested unless the initial level exceeded 103 cfu/10g of sprouts. Based on these results we suggest BPW-S for a one-broth enrichment strategy of stressed Gram-negative foodborne pathogens from dry products. However, a one-broth enrichment strategy based on BPW variants tested in this evaluation is not recommended for produce with a high level of Gram-negative background flora due to very high detection limits.


      PubDate: 2015-08-11T12:47:27Z
       
  • Identification and quantification of the caproic acid-producing bacterium
           Clostridium kluyveri in the fermentation of pit mud used for Chinese
           strong-aroma type liquor production
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Xiao-long Hu, Hai Du, Yan Xu
      Chinese strong-aroma type liquor (CSAL) is a popular distilled alcoholic beverage in China. It is produced by a complex fermentation process that is conducted in pits in the ground. Ethyl caproate is a key flavor compound in CSAL and is thought to originate from caproic acid produced by Clostridia inhabiting the fermentation pit mud. However, the particular species of Clostridium associated with this production are poorly understood and problematic to quantify by culturing. In this study, a total of 28 closest relatives including 15 Clostridia and 8 Bacilli species in pit muds from three CSAL distilleries, were detected by culture-dependent and -independent methods. Among them, Clostridium kluyveri was identified as the main producer of caproic acid. One representative strain C. kluyveri N6 could produce caproic, butyric and octanoic acids and their corresponding ethyl esters, contributing significantly to CSAL flavor. A real time quantitative PCR assay of C. kluyveri in pit muds developed showed that a concentration of 1.79×107 16S rRNA gene copies/g pit mud in LZ-old pit was approximately six times higher than that in HLM and YH pits and sixty times higher than that in LZ-new pit respectively. This method can be used to improve the management of pit mud microbiology and its impact on CSAL quality.


      PubDate: 2015-08-11T12:47:27Z
       
  • Clustered array of ochratoxin A biosynthetic genes in Aspergillus steynii
           and their expression patterns in permissive conditions
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Jessica Gil-Serna, Covadonga Vázquez, María Teresa González-Jaén, Belén Patiño
      Aspergillus steynii is probably the most relevant species of section Circumdati producing ochratoxin A (OTA). This mycotoxin contaminates a wide number of commodities and it is highly toxic for humans and animals. Little is known on the biosynthetic genes and their regulation in Aspergillus species. In this work, we identified and analysed three contiguous genes in A. steynii using 5′-RACE and genome walking approaches which predicted a cytochrome P450 monooxygenase (p450ste), a non-ribosomal peptide synthetase (nrpsste) and a polyketide synthase (pksste). These three genes were contiguous within a 20742bp long genomic DNA fragment. Their corresponding cDNA were sequenced and their expression was analysed in three A. steynii strains using real time RT-PCR specific assays in permissive conditions in in vitro cultures. OTA was also analysed in these cultures. Comparative analyses of predicted genomic, cDNA and amino acid sequences were performed with sequences of similar gene functions. All the results obtained in these analyses were consistent and point out the involvement of these three genes in OTA biosynthesis by A. steynii and showed a co-ordinated expression pattern. This is the first time that a clustered organization OTA biosynthetic genes has been reported in Aspergillus genus. The results also suggested that this situation might be common in Aspergillus OTA-producing species and distinct to the one described for Penicillium species.


      PubDate: 2015-08-11T12:47:27Z
       
  • Exopolysaccharides from co-cultures of Weissella confusa 11GU-1 and
           Propionibacterium freudenreichii JS15 act synergistically on wheat dough
           and bread texture
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Saskia Katharina Tinzl-Malang, Peter Rast, Franck Grattepanche, Janice Sych, Christophe Lacroix
      The storage of bread is limited by both physical (staling) and microbial (mainly fungal) spoilage. Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) and organic acids from propionibacteria (PAB) have been used to enhance texture and extend shelf-life of bakery products. In this study the functionality of EPS of Weissella confusa A3/2-1 (dextran), W. confusa F3/2-2 (dextran and levan), W. confusa 11GU-1 (dextran and ropy capsular polysaccharide) was evaluated in wheat bread. Two strains of Propionibacterium freudenreichii (Pf), shown to produce a heteropolysaccharide (Pf JS15) or a β-glucan (Pf DF30), were tested in single and mixed cultures with W. confusa (Wc). The EPS fermentates were prepared by batch fermentation of cereal- or malt-based medium using sucrose (Wc) or lactic acid (Pf) as carbon source. Incorporation of EPS from single culture fermentates and 1:1 Weissella–Propionibacterium fermentate mixtures revealed strong positive effects of dextran and ropy capsular polysaccharide produced by Wc 11GU-1 on bread staling retardation, with synergistic effects of EPS mixture from Wc 11GU-1 and Pf JS15. A co-fermentation of Wc 11GU-1 and Pf JS15 was developed to produce EPS together with antifungal organic acid mixture (acetate and propionate) in a single step process. The addition of 15% (w/w flour base) co-culture, yielding EPS, acetate and propionate concentrations of 1.5, 0.5 and 1g/kg dough, respectively, resulted in improved bread texture, increased loaf volume and decreased crumb firming during storage for 3days compared with control breads and breads supplemented with equivalent levels of chemical organic acids. Our data showed that EPS could compensate for the negative effects of chemical acetate and propionate in a concentration range exerting antifungal effects. The natural bioingredient produced by Wc 11GU-1 and Pf JS15 has potential for applications as antifungal, texture-building and anti-staling agent in breads, consistent with consumer demands for clean label products.


      PubDate: 2015-08-05T20:21:11Z
       
  • Detection of Yersinia enterocolitica in milk powders by cross-priming
           amplification combined with immunoblotting analysis
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Hongwei Zhang, Shaolong Feng, Yulong Zhao, Shuo Wang, Xiaonan Lu
      Yersinia enterocolitica (Y. enterocolitica) is frequently isolated from a wide variety of foods and can cause human yersiniosis. Biochemical and culture-based assays are common detection methods, but require a long incubation time and easily misidentify Y. enterocolitica as other non-pathogenic Yersinia species. Alternatively, cross-priming amplification (CPA) under isothermal conditions combined with immunoblotting analysis enables a more sensitive detection in a relatively short time period. A set of specific displacement primers, cross primers and testing primers was designed on the basis of six specific sequences in Y. enterocolitica 16S–23S rDNA internal transcribed spacer. Under isothermal condition, amplification and hybridization were conducted simultaneously at 63°C for 60min. The specificity of CPA was tested for 96 different bacterial strains and 165 commercial milk powder samples. Two red lines were developed on BioHelix Express strip for all of the Y. enterocolitica strains, and one red line was shown for non-Y. enterocolitica strains. The limit of detection of CPA was 100 fg for genomic DNA (1000 times more sensitive than PCR assay), 101 CFU/ml for pure bacterial culture, and 100 CFU per 100g milk powder with pre-enrichment at 37°C for 24h. CPA combined with immunoblotting analysis can achieve highly specific and sensitive detection of Y. enterocolitica in milk powder in 90min after pre-enrichment.


      PubDate: 2015-08-05T20:21:11Z
       
  • Osmotolerance provided by the alternative sigma factors σB and rpoS
           to Staphylococcus aureus and Escherichia coli is solute dependent and does
           not result in an increased growth fitness in NaCl containing media
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): G. Cebrián, C. Arroyo, S. Condón, P. Mañas
      The aim of this work was to examine the role of the alternative general stress sigma factors σB and rpoS on the ability of Staphylococcus aureus and Escherichia coli, respectively, to grow in liquid and solid media of different osmolarity. For this purpose, S. aureus strain Newman and its isogenic ΔsigB mutant IK84 and E. coli strain BJ4 and its isogenic ΔrpoS mutant BJ4L1 were grown in media (TSBYE) with different concentrations of NaCl. Growth parameters (lag phase duration, growth rate and maximum number of microorganisms) and limiting growth concentrations (Maximum Non-Inhibitory Concentration – MNIC – and Minimum Inhibitory Concentration – MIC–) were determined. The mechanisms underlying the differences observed between parental and mutant strains were also explored. The absence of the sigma factors σB and rpoS led to a decrease in the MNICs and MICs calculated for S. aureus and E. coli, respectively. Conversely, neither σB nor rpoS provided with increased growth fitness to S. aureus and E. coli cells at NaCl concentrations up to 1.36M and 1M, respectively. The decreased osmotolerance of the σB and rpoS deficient strains, as compared to their parental strains, was compensated by the addition of glycine-betaine (1mM) to the growth medium. It was also observed that the decreased tolerance to NaCl of the mutant strains was coincident with a decreased tolerance to sucrose, KCl, and LiCl but not to glycerol, MgCl2, and CaCl2. Results obtained also demonstrate that the increased osmotolerance of stationary growth phase E. coli cells, as compared to exponential growth phase ones, would be due to the activation of both rpoS-independent and rpoS-dependent mechanisms. This work will help to understand the mechanisms of bacterial resistance to osmotic stress and the role of the alternative sigma factors σB and rpoS in this process.


      PubDate: 2015-08-05T20:21:11Z
       
  • The significance of clean and dirty animals for bacterial dynamics along
           the beef chain
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Sigrun J. Hauge, Truls Nesbakken, Birgitte Moen, Ole-Johan Røtterud, Sissel Dommersnes, Ole Nesteng, Øyvin Østensvik, Ole Alvseike
      This study investigated the bacterial dynamics along the beef chain for clean and dirty cattle in the slaughter and processing lines, using classic quantitative methods and molecular analyses. In addition, the Norwegian national guidelines for Good Hygiene Practices in Norway were evaluated. In these guidelines, cattle presented for slaughter are categorised according to hide cleanliness, resulting in separate processing lines for meat from very dirty animals and reduced prices to farmers. The study was conducted in two commercial abattoirs in Norway. Two groups were compared; 40 visually clean cattle and 40 visually dirty cattle presented for slaughter, with 20 from each group at each abattoir. The same animals were sampled at five sampling sites: hides, carcass surfaces after dehiding, just before chilling, after chilling, and meat trimmings. Meat trimmings were sampled in only one abattoir. Three hundred and sixty samples were collected by swabbing 100cm2 of the brisket area at the first four sampling sites, and sampling 200g of meat trimmings at the fifth site. The results showed that the hides of dirty cattle had more Enterobacteriaceae and higher Aerobic Plate Counts (APC) than visually clean cattle (P<0.05), however there was no significant difference for Escherichia coli. For the other sampling sites, there were no differences between the dirty and the clean group. An effect of chilling/drying of the carcass surfaces was demonstrated by the significant reduction in the number of carcasses on which E. coli and Enterobacteriaceae were detected; from 11% and 39% before chilling to 1% and 16% after chilling, respectively. Enterobacteriaceae and E. coli were detected in only three and one of the meat trimming samples, respectively. Amplification and sequencing of the 16S rRNA gene from 643 Enterobacteriaceae colonies derived from 107 samples demonstrated that Escherichia/Shigella were dominant within this family on the hides. However, after dehiding, after grading, and after chilling, the genera Citrobacter and Enterobacter dominated. The meat trimmings were dominated by the genera Kluyvera, Hafnia, and unclassified Enterobacteriaceae. The relative proportions of Escherichia/Shigella were higher for dirty animals than for clean animals, and were higher on hides than from sampling sites further down the chain (P<0.05). The minor differences in contamination on carcass surfaces and meat trimmings between clean and dirty cattle indicate that separate processing lines in Norwegian abattoirs seem to be unnecessary.


      PubDate: 2015-08-04T03:24:59Z
       
  • Production and partial characterization of exopolysaccharides produced by
           two Lactobacillus suebicus strains isolated from cider
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Idoia Ibarburu, Ana Isabel Puertas, Iñaki Berregi, Miguel A. Rodríguez-Carvajal, Alicia Prieto, Mª. Teresa Dueñas
      Many lactic acid bacteria synthesize extracellular polysaccharides (exopolysaccharides, EPSs) with a large variation in structure and potential functional properties. Although EPS production can produce detrimental effects in alcoholic beverages, these polymers play an important role in the rheological behavior and texture of fermented products. In this work, EPS production by two Lactobacillus suebicus strains, which were isolated from ropy ciders, was examined in a semidefined medium. The existence of priming glycosyltransferase encoding genes was detected by PCR. In addition, the preliminary characterization of the polymers was undertaken. Molecular masses were determined by size exclusion chromatography revealing the presence of two peaks, corresponding to polymers of high- and low-molecular-weight in all fractions. The composition of the EPS fractions was analyzed by gas chromatography–mass spectrometry after acid hydrolysis, revealing that they contained glucose, galactose, N-acetylglucosamine and phosphate, although in different ratios, suggesting that a mixture of polysaccharides is being synthesized. We also examined the influence of the sugar source (glucose, ribose, xylose, or arabinose) and pH conditions on growth and EPS production.


      PubDate: 2015-08-04T03:24:59Z
       
  • Diversity and dynamics of antibiotic-resistant bacteria in cheese as
           determined by PCR denaturing gradient gel electrophoresis
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Ana Belén Flórez, Baltasar Mayo
      This work reports the composition and succession of tetracycline- and erythromycin-resistant bacterial communities in a model cheese, monitored by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Bacterial 16S rRNA genes were examined using this technique to detect structural changes in the cheese microbiota over manufacturing and ripening. Total bacterial genomic DNA, used as a template, was extracted from cultivable bacteria grown without and with tetracycline or erythromycin (both at 25μgml−1) on a non-selective medium used for enumeration of total and viable cells (Plate Count agar with Milk; PCA-M), and from those grown on selective and/or differential agar media used for counting various bacterial groups; i.e., lactic acid bacteria (de Man, Rogosa and Sharpe agar; MRSA), micrococci and staphylococci (Baird–Parker agar; BPA), and enterobacteria (Violet Red Bile Glucose agar; VRBGA). Large numbers of tetracycline- and erythromycin-resistant bacteria were detected in cheese samples at all stages of ripening. Counts of antibiotic-resistant bacteria varied widely depending on the microbial group and the point of sampling. In general, resistant bacteria were 0.5–1.0Log10 units fewer in number than the corresponding susceptible bacteria. The PCR-DGGE profiles obtained with DNA isolated from the plates for total bacteria and the different bacterial groups suggested Escherichia coli, Lactococcus lactis, Enterococcus faecalis and Staphylococcus spp. as the microbial types resistant to both antibiotics tested. This study shows the suitability of the PCR-DGGE technique for rapidly identifying and tracking antibiotic resistant populations in cheese and, by extension, in other foods.


      PubDate: 2015-08-04T03:24:59Z
       
  • Precursors and metabolic pathway for guaiacol production by
           Alicyclobacillus acidoterrestris
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Rui Cai, Yahong Yuan, Zhouli Wang, Chunfeng Guo, Bin Liu, Laping Liu, Yutang Wang, Tianli Yue
      Alicyclobacillus acidoterrestris has recently received much attention due to its implication in the spoilage of pasteurized fruit juices, which was manifested by the production of guaiacol. Vanillic acid and vanillin have been accepted as the biochemical precursors of guaiacol in fruit juices. The purpose of this study was to try to find other precursors and elucidate details about the conversion of vanillic acid and vanillin to guaiacol by A. acidoterrestris. Four potential substrates including ferulic acid, catechol, phenylalanine and tyrosine were analyzed, but they could not be metabolized to guaiacol by all the thirty A. acidoterrestris strains tested. Resting cell studies and enzyme assays demonstrated that vanillin was reduced to vanillyl alcohol by NADPH-dependent vanillin reductase and oxidized to vanillic acid by NAD(P)+-dependent vanillin dehydrogenases in A. acidoterrestris DSM 3923. Vanillic acid underwent a nonoxidative decarboxylation to guaiacol. The reversible vanillic acid decarboxylase involved was oxygen insensitive and pyridine nucleotide-independent.


      PubDate: 2015-08-04T03:24:59Z
       
  • Impact of growth temperature and surface type on the resistance of
           Pseudomonas aeruginosa and Staphylococcus aureus biofilms to disinfectants
           
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Marwan Abdallah, Oussama Khelissa, Ali Ibrahim, Corinne Benoliel, Laurent Heliot, Pascal Dhulster, Nour-Eddine Chihib
      Biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus on food-contact-surfaces represents a significant risk for the public health. In this context, the present study investigates the relationship between the environmental conditions of biofilm formation and the resistance to disinfectants. Therefore, a static biofilm reactor, called NEC-Biofilm System, was established in order to study the effect of growth temperature (20, 30 and 37°C), and of the surface type (stainless steel and polycarbonate), on biofilm resistance to disinfectants. These conditions were selected to mimic the biofilm formation on abiotic surfaces of food processing industries. The antibiofilm assays were performed on biofilms grown during 24h. The results showed that the growth temperature influenced significantly the biofilm resistance to disinfectants. These data also revealed that the growth temperature has a significant effect on the biofilm structure of both bacteria. Furthermore, the increase of the biofilm growth temperature increased significantly the algD transcript level in sessile P. aeruginosa cells, whereas the icaA one was not affected in S. aureus cells. Overall, our findings show that the biofilm structure and matrix cannot fully explain the biofilm resistance to disinfectant agents. Nevertheless, it underlines the intimate link between environmental conditions, commonly met in food sectors, and the biofilm resistance to disinfectants.


      PubDate: 2015-07-30T20:52:09Z
       
  • Inactivation of Bacillus subtilis spores by combined pulsed light and
           thermal treatments
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Mari Luz Artíguez, Iñigo Martínez de Marañón
      The combined effect of pulsed light (PL) and heat processing was evaluated on the inactivation of Bacillus subtilis spores. Those processes were applied separately and the time between both treatments was modified to evaluate whether the effect of the first treatment is maintained for a long time. B. subtilis spores subjected to sublethal pre-treatments were more sensitive to subsequent treatments (PL or thermal treatments) than untreated spores. Heating followed by PL was the most effective combination in reducing B. subtilis counts. Bacterial spores remained sensitized to subsequent treatment for at least 24h of storage in water, whatever the temperature was (4 or 30°C). Sensitivity of B. subtilis cells to PL or heat processing increased after germination in a nutrient broth, being equally sensitive from 3 to 24h. Vegetative cells maintained their enhanced sensitivity to subsequent processing after spore germination. The results of this work demonstrate that the combination of heating and PL treatment is a promising preservation method for microbial inactivation.


      PubDate: 2015-07-30T20:52:09Z
       
  • Biopreservative methods to control the growth of foodborne pathogens on
           fresh-cut lettuce
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): M. Oliveira, M. Abadias, P. Colás-Medà, J. Usall, I. Viñas
      Fruits and vegetables can become contaminated by foodborne pathogens such as Escherichia coli O157:H7, Salmonella and Listeria monocytogenes, and it has been demonstrated that current industrial sanitizing treatments do not eliminate the pathogens when present. Chemical control is widely used, but biological control appears to be a better solution, mainly using the native microbiota present on fresh produce. The first objective of this study was to isolate native microbiota from whole and fresh-cut produce and to determine whether these bacteria were antagonistic toward foodborne pathogens. A total of 112 putative antagonist isolates were screened for their ability to inhibit the growth of Salmonella enterica on lettuce disks. Five different genera reduced S. enterica growth more than 1-log unit at 20°C at the end of 3days. When tested against L. monocytogenes 230/3, only Pseudomonas sp. strain M309 (M309) was able to reduce pathogen counts by more than 1-log unit. Therefore, M309 strain was selected to be tested on lettuce disks at 10°C against S. enterica, E. coli O157:H7 and L. monocytogenes. M309 strain was only able to reduce S. enterica and E. coli O157:H7 populations. The second objective was to test different biopreservative methods including M309 strain, Pseudomonas graminis CPA-7 (CPA-7), bacteriophages (Listex P100 and Salmonelex) and nisin at conditions simulating commercial applications against Salmonella and L. monocytogenes on fresh-cut lettuce. The addition of the biopreservative agents did not result in a significant reduction of Salmonella population. However, CPA-7 strain together with nisin reduced L. monocytogenes numbers after 6days of storage at 10°C. The cocktail of Salmonella and L. monocytogenes was not markedly inactivated by their respective bacteriophage solutions. This study highlighted the potential of biocontrol, but the combination with other technologies may be required to improve their application on fresh-cut lettuce.


      PubDate: 2015-07-26T21:50:07Z
       
  • Usefulness of pulsed-field gel electrophoresis profiles for the
           determination of Salmonella serovars
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Chien-Shun Chiou, Mia Torpdahl, Ying-Shu Liao, Chun-Hsing Liao, Chi-Sen Tsao, Shiu-Yun Liang, You-Wun Wang, Jung-Che Kuo, Yen-Yi Liu
      We created a database consisting of a large number of Salmonella pulsed-field gel electrophoresis (PFGE) profiles covering a wide range of different serovars. This database was used for the prediction of the serovars based on the PFGE profiles for isolates from Taiwan and Denmark. The PFGE profiles proved very useful in the determination of a serovar although serovar prediction was more efficient for local isolates than those from a distant geographic area. To use a highly stringent band matching tolerance in the BioNumerics software is also important for the grouping of serovars.


      PubDate: 2015-07-26T21:50:07Z
       
  • Prevalence and diversity of enterotoxin genes with genetic background of
           Staphylococcus aureus isolates from different origins in China
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Guoxiang Chao, Guangyu Bao, Yongzhong Cao, Wenguang Yan, Yan Wang, Xiaorong Zhang, Liping Zhou, Yantao Wu
      Staphylococcal enterotoxins (SE) induce toxin-mediated diseases, such as food poisoning. In the present study, 568 isolates from different sources were tested for the prevalence of 18 SE genes and performed spa typing. In addition, we characterized the relationships between the distribution of SE genes and molecular clones based on multilocus sequence typing (MLST), spa and staphylococcal cassette chromosome mec (SCCmec) typing in selected 250 isolates. Approximately 54.40% of the isolates from different sources harbored one or more SE genes forming 120 distinct gene profiles. Seven genes, sea, seb, seg, seo, sem, seq, and sel were more frequently detected. The distributions of the SE genes among the isolates from human, animals, and foodborne origins were highly different with isolates from environments (P < 0.01). The classic SE genes in both foodborne and human origin isolates were significantly higher than that in animal origin isolates (P < 0.01), whereas the prevalence of genes of egc cluster and the other genes was similar in human, animal, and foodborne origin isolates (P > 0.05). We identified two important gene clusters, sea–sek–seq, which is closely related to hospital-acquired (HA) methicillin-resistant Staphylococcus aureus (MRSA)-III, and the egc cluster, which accounts for nearly half of all genes. Approximately 71% isolates could be typed by spa, yielding 103 spa types, of which 18 spa types were primary types. In clonal complex (CC) 239, an important Asian HA-MRSA-III clone from humans, nearly all isolates harbored complete or partial sea-sek-seq cluster; the main spa types were t030 and t037. In CC630, an important new community-associated (CA) MRSA-V CC in China, only sporadic SE genes, three main spa types, t4549, t2196, and t377 were observed. The egc cluster coexisting with other genes was present in isolates of CC5, CC9, CC1281, CC1301, CC30 and sequence type (ST) 25, but completely absent in isolates of CC239, CC59, CC7, and CC88. The results illustrate the genetic clonal diversity and the identity of S. aureus isolates from different sources with respect to SE genes and highlight a correlation between SE genes or gene clusters and CCs, spa, and MRSA clones. The foodborne and human origin isolates were the main potential causes of classic staphylococcal foodborne poisonings, whereas isolates harboring novel genes were new potential hazards to food safety.


      PubDate: 2015-07-26T21:50:07Z
       
  • Use of phytic acid and hyper-salting to eliminate Escherichia coli O157:H7
           from napa cabbage for kimchi production in a commercial plant
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Nam Hee Kim, Seong Ho Jang, Soon Han Kim, Hee Jung Lee, Younghoon Kim, Jee Hoon Ryu, Min Suk Rhee
      The aim of this study was to develop a new salting method using natural phytic acid (PA) to ensure the microbiological safety and quality of salted napa cabbage used for kimchi production. The production of salted napa cabbage involves several stages: trimming, hyper-salting (20% NaCl) for up to 1h, salting (10% NaCl for 10–18h), three sequential washes in water (30s for each), and draining (2h). Two separate experiments were performed: one to determine the appropriate treatment conditions and a second to validate applicability under commercial conditions. In Experiment I, the effects of hyper-salting with PA on Escherichia coli O157:H7 numbers were tested in the laboratory. The following variables were monitored: 1) PA concentration (1, 2, 3%, w/w); 2) the ratio of the sample weight to the total volume of the solution (1:1.5, 1:3, or 1:6); 3) the hyper-salting time (30 or 60min); and 4) the salting time (2, 5, or 8h). A procedure that achieved a >5-log reduction in the E. coli O157:H7 population was then tested in an actual kimchi processing plant (Experiment II). The results from Experiment I showed that bactericidal efficacy increased as all the measured variables increased (p <0.05). Hyper-salting with 2% PA at a sample-to-water ratio (w/v) of 1:3 and 1:6 for 60min resulted in a >5-logCFU/g reduction in the E. coli O157:H7 population. Further salting for 5h completely eliminated (<1-logCFU/g) all bacteria. Thus, hyper-salting with PA 2% at a sample-to-water ratio of 1:3 for 60min, followed by salting for 5h, was tested under large-scale production conditions. The results revealed that the initial aerobic plate counts (APC), total coliform counts (TC), and fecal coliform counts (FC) were 6.6, 3.4, and 2.8-logCFU/g, respectively. The selected protocol reduced these values by 3.7-, >2.4-, and >1.8-logCFU/g, respectively. The 5h salting step maintained the TC and FC at <1-logCFU/g; however, the APC recovered somewhat. The pH and salinity of the treated salted napa cabbages were within the ranges required for kimchi production (pH5.1–5.3 and 1.5–2.0%, respectively). These results suggest that this novel method of salting food ensures microbiological safety and reduces the production time.


      PubDate: 2015-07-26T21:50:07Z
       
  • Characterization of extended-spectrum β-lactamase (ESBL) producing
           non-typhoidal Salmonella (NTS) from imported food products
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Dongryeoul Bae, Chorng-Ming Cheng, Ashraf A. Khan
      Food contaminated with extended-spectrum β-lactamase (ESBL)-producing Salmonella enterica has emerged as an important global issue due to the international food-product trade. Therefore, the purpose of this study was to investigate whether imported food products can serve as a reservoir for non-typhoidal Salmonella (NTS) that can transmit β-lactam-resistance to humans through ingestion of the contaminated food. NTS isolates (n =110) were collected from various imported food products (n =3480) from 2011 to 2013. The NTS isolates were analyzed by serotyping, antimicrobial susceptibility tests, and plasmid profiling. Salmonella ser. Weltevreden, Salmonella ser. Newport, Salmonella ser. Senftenberg, Salmonella ser. Virchow, Salmonella ser. Enteritidis, Salmonella ser. Typhimurium, and Salmonella ser. Bareilly were the most prevalent serovars. Nine NTS strains were resistant to ampicillin and/or one or more cephalosporins (MIC>32μg/mL). Polymerase chain reaction (PCR) detection revealed that all nine isolates carried the bla TEM-1 β-lactamase gene, with or without the bla CTX-M-9 or bla OXA-1 genes. Two isolates, PSS_913 and PSS_988, exhibited decreased susceptibility to extended-spectrum cephalosporins and ampicillin. Plasmids ranging in size from less than 8 to over 165kbp, from all of the 9 resistant isolates, belonged to the IncHI1, IncI1, IncN, or IncX groups. Conjugation experiments and Southern hybridization, using bla TEM-1, confirmed the plasmid-mediated transfer of ESBL genes, which resulted in increased MICs of β-lactams for Escherichia coli transconjugants. The contamination of imported food products by NTS with conjugative plasmid-borne ESBL genes may contribute to the spread of ESBL-producing NTS and compromise the therapeutic activity of extended-spectrum β-lactam antibiotics.


      PubDate: 2015-07-26T21:50:07Z
       
  • Application of water-assisted ultraviolet light processing on the
           inactivation of murine norovirus on blueberries
    • Abstract: Publication date: 2 December 2015
      Source:International Journal of Food Microbiology, Volume 214
      Author(s): Chuhan Liu, Xinhui Li, Haiqiang Chen
      In this study, a novel set-up using water-assisted UV processing was developed and evaluated for its decontamination efficacy against murine norovirus (MNV-1) inoculated on fresh blueberries for both small and large-scale experimental setups. Blueberries were skin-inoculated with MNV-1 and treated for 1–5min with UV directly (dry UV) or immersed in agitated water during UV treatment (water-assisted UV). The effect of the presence of 2% (v/v) blueberry juice or 5% crushed blueberries (w/w) in wash water was also evaluated. Results showed that water-assisted UV treatment generally showed higher efficacies than dry UV treatment. With 12,000J/m2 UV treatment in small-scale setup, MNV reductions of >4.32- and 2.48-log were achieved by water-assisted UV and dry UV treatments, respectively. Water-assisted UV showed similar inactivating efficacy as 10-ppm chlorine wash. No virus was detected in wash water after UV treatment or chlorine wash. MNV-1 was more easily killed on skin-inoculated blueberries compared with calyx-inoculated berries. When clear water was used as wash water in the large-scale setup, water-assisted UV treatment (UV dose of 12,000J/m2) resulted in >3.20 log and 1.81 log MNV-1 reductions for skin- and calyx-inoculated berries, respectively. The presence of 2% blueberry juice in wash water decreased the decontamination efficacy of water-assisted UV and chlorine washing treatments. To improve the inactivation efficacy, the effect of combining water-assisted UV treatment with chlorine washing was also evaluated. The combined treatment had better or similar inactivation efficacy compared to water-assisted UV treatment and chlorine washing alone. Findings of this study suggest that water-assisted UV treatment could be used as an alternative to chlorine washing for blueberries and potentially for other fresh produce.


      PubDate: 2015-07-26T21:50:07Z
       
  • Editorial Board
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210




      PubDate: 2015-07-22T21:46:54Z
       
  • Identification and characterization of tetracycline resistance in
           Lactococcus lactis isolated from Polish raw milk and fermented artisanal
           products
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Joanna Zycka-Krzesinska, Joanna Boguslawska, Tamara Aleksandrzak-Piekarczyk, Jakub Jopek, Jacek K. Bardowski
      To assess the occurrence of antibiotic-resistant Lactic Acid Bacteria (LAB) in Polish raw milk and fermented artisanal products, a collection comprising 500 isolates from these products was screened. Among these isolates, six strains (IBB28, IBB160, IBB161, IBB224, IBB477 and IBB487) resistant to tetracycline were identified. The strains showing atypical tetracycline resistance were classified as Lactococcus lactis: three of them were identified as L. lactis subsp. cremoris (IBB224, IBB477 and IBB487) and the other three (IBB28, IBB160, IBB161) were identified as L. lactis subsp. lactis. The mechanism involving Ribosomal Protection Proteins (RPP) was identified as responsible for tetracycline resistance. Three of the tested strains (IBB28, IBB160 and IBB224) had genes encoding the TetS protein, whereas the remaining three (IBB161, IBB477 and IBB487) expressed TetM. The results also demonstrated that the genes encoding these proteins were located on genetic mobile elements. The tet(S) gene was found to be located on plasmids, whereas tet(M) was found within the Tn916 transposon.


      PubDate: 2015-07-22T21:46:54Z
       
  • Diversity of Saccharomyces cerevisiae strains isolated from Borassus
           akeassii palm wines from Burkina Faso in comparison to other African
           beverages
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): François Tapsoba, Jean-Luc Legras, Aly Savadogo, Sylvie Dequin, Alfred Sababenedyo Traore
      In South-West of Burkina Faso, palm wine is produced by spontaneous fermentation of the sap from a specific palm tree Borassus akeassii and plays an important role in people's lives. Saccharomyces cerevisiae is the main agent of this alcoholic fermentation but little is known about the diversity of the isolates from palm. In this work, 39 Saccharomyces cerevisiae strains were isolated from palm wine samples collected from 14 sites in Burkina Faso, as well as 7 isolates obtained from sorghum beer (Dolo) from 3 distant sites. Their diversity was analyzed at 12 microsatellite loci, and compared to the genotypes obtained for other African yeast populations isolated from Cocoa hulks from Ghana, sorghum beer from Ivory Coast, palm wine from Djibouti Republic, and to our database of strains from miscellaneous origins (bread, beer, wine, sake, oaks…). The ploidy of these strains has been assessed as well by flow cytometry. Our results show that B. akeassii palm wine contains a specific yeast population of diploid strains, different from Dolo produced in the same area and from other palm wine strains from Ivory Coast, Nigeria, or Djibouti Republic. In contrast, Dolo strains appeared as a group of related and mainly tetraploid strains despite being isolated from different countries.


      PubDate: 2015-07-18T21:38:42Z
       
  • Empirical model based on Weibull distribution describing the destruction
           kinetics of natural microbiota in pineapple (Ananas comosus L.) puree
           during high-pressure processing
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Snehasis Chakraborty, Pavuluri Srinivasa Rao, Hari Niwas Mishra
      High pressure inactivation of natural microbiota viz. aerobic mesophiles (AM), psychrotrophs (PC), yeasts and molds (YM), total coliforms (TC) and lactic acid bacteria (LAB) in pineapple puree was studied within the experimental domain of 0.1–600MPa and 30–50°C with a treatment time up to 20min. A complete destruction of yeasts and molds was obtained at 500MPa/50°C/15min; whereas no counts were detected for TC and LAB at 300MPa/30°C/15min. A maximum of two log cycle reductions was obtained for YM during pulse pressurization at the severe process intensity of 600MPa/50°C/20min. The Weibull model clearly described the non-linearity of the survival curves during the isobaric period. The tailing effect, as confirmed by the shape parameter (β) of the survival curve, was obtained in case of YM (β <1); whereas a shouldering effect (β >1) was observed for the other microbial groups. Analogous to thermal death kinetics, the activation energy (E a, kJ·mol−1) and the activation volume (V a, mL·mol−1) values were computed further to describe the temperature and pressure dependencies of the scale parameter (δ, min), respectively. A higher δ value was obtained for each microbe at a lower temperature and it decreased with an increase in pressure. A secondary kinetic model was developed describing the inactivation rate (k, min−1) as a function of pressure (P, MPa) and temperature (T, K) including the dependencies of E a and V a on P and T, respectively.


      PubDate: 2015-07-18T21:38:42Z
       
  • A highly sensitive and flexible magnetic nanoprobe labeled
           
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Yingying Liu, Zhaohuan Zhang, Yilong Wang, Yong Zhao, Ying Lu, Xiaowei Xu, Jun Yan, Yingjie Pan
      A magnetic nanoprobe labeled immunochromatographic test strip (MNP/ICTS) was developed to detect food-borne pathogen Vibrio parahaemolyticus. Specific antibody against V. parahaemolyticus was used as test line by coating onto the nitrocellulose membrane. Magnetic nanoprobe was prepared by immobilizing the specific antibody onto the surface of superparamagnetic nanoparticles. Specificity and sensitivity of the MNP/ICTS system were verified by artificially contaminated shrimp homogenate samples. Reliability and application feasibility of the MNP/ICTS system were demonstrated by using seafood samples (n=36). Comparing with polymerase chain reaction (PCR) and traditional culture methods, the MNP/ICTS system is found to be not only a rapid qualitative analysis (~10min), but also an accurately quantitative detection platform. Through its rapid magnetic separation property, the MNP/ICTS system is capable to flexibly combine with a sample enrichment and pre-incubation process. This combination makes the qualitative sensitivity for the food samples surged more than 100-fold. A naked-eye observation of 1.58×102 CFU/g V. parahaemolyticus was realized. This sensitivity could meet the V. parahaemolyticus test threshold value in many countries. Also, the total sample pre-treatment plus MNP/ICTS assay only needs about 4.5h. Namely, we can get test results in a day. Hence, the developed MNP/ICTS assay platform is simple, rapid and highly sensitive. It is a flexible test platform for pathogen detection. The favorable comparison with PCR and culture methods further proves that the developed MNP/ICTS is applicable into food-borne pathogen or other areas where a simple, rapid, sensitive and point-of-care analysis is desirable.
      Graphical abstract image

      PubDate: 2015-07-18T21:38:42Z
       
  • Attachment and localization of human norovirus and animal caliciviruses in
           fresh produce
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Erin DiCaprio, Anastasia Purgianto, Yuanmei Ma, John Hughes, Xiangjun Dai, Jianrong Li
      Fresh produce is a high risk food for human norovirus (NoV) contamination. To help control this pathogen in fresh produce, a better understanding of the interaction of human NoV and fresh produce needs to be established. In this study the attachment of human NoV and animal caliciviruses (murine norovirus, MNV-1; Tulane virus, TV) to fresh produce was evaluated, using both visualization and viral enumeration techniques. It was found that a human NoV GII.4 strain attached efficiently to the Romaine lettuce leaves and roots and green onion shoots, and that washing with PBS or 200ppm of chlorine removed less than 0.4log of viral RNA copies from the tissues. In contrast, TV and MNV-1 bound more efficiently to Romaine lettuce leaves than to the roots, and simple washing removed less than 1log of viruses from the lettuce leaves and 1–4logPFU of viruses from roots. Subsequently, the location of virus particles in fresh produce was visualized using a fluorescence-based Quantum Dots (Q-Dots) assay and confocal microscopy. It was found that human NoV virus-like particles (VLPs), TV, and MNV-1 associated with the surface of Romaine lettuce and were found aggregating in and around the stomata. In green onions, human NoV VLPs were found between the cells of the epidermis and cell walls of both the shoots and roots. However, TV and MNV-1 were found to be covering the surface of the epidermal cells in both the shoots and roots of green onions. Collectively, these results demonstrate that (i) washing with 200ppm chlorine is ineffective in removing human NoV from fresh produce; and (ii) different viruses vary in their localization patterns to different varieties of fresh produce


      PubDate: 2015-07-18T21:38:42Z
       
  • Molecular detection of Cyclospora in water, soil, vegetables and humans in
           southern Italy signals a need for improved monitoring by health
           authorities
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Annunziata Giangaspero, Marianna Marangi, Anson V. Koehler, R. Papini, G. Normanno, V. Lacasella, A. Lonigro, Robin B. Gasser
      To date, in Europe, there is scant information on the occurrence of Cyclospora in water from treatment plants and in humans, and no data are available on soil or fresh plant products. Here, we undertook the first molecular survey of Cyclospora in multiple biological matrices collected from the Apulia region of southern Italy. Samples of irrigation water from four municipal treatment plants, eight different types of vegetables or fruit (cucumber, lettuce, fennel, celery, tomato, melon, endive and chicory) and soil from the same farms on which these plants were grown, as well as faecal samples from humans living in the same region were tested by qPCR-coupled single-strand conformation polymorphism (SSCP) analysis and DNA sequencing. Cyclospora was detected in 15.5% of all 213 samples tested. Specifically, this protist was detected in (i) treated water (21.3% of 94 samples), well water (6.2% of 16), but not drinking water (0% of 3); (ii) soil (11.8% of 51 samples) and vegetables (12.2% of 49), with the highest prevalence (18.7%) on fennel; and (iii) human stools (27.5% of 40 samples). In environmental and food samples, Cyclospora was detected mainly in autumn and was significantly more prevalent in the faeces from humans of 40–50years of age. This is the first comprehensive molecular survey of Cyclospora in environmental, food and human faecal samples in Europe. These data suggest that irrigation water, soil and vegetables might be contaminated by Cyclospora cayetanensis, which might represent a source of infection to humans in the study area and calls for monitoring by health authorities.


      PubDate: 2015-07-18T21:38:42Z
       
  • Modeling red cabbage seed extract effect on Penicillium corylophilum:
           
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Stéphane Dagnas, Maria Gougouli, Bernard Onno, Konstantinos P. Koutsoumanis, Jeanne-Marie Membré
      The inhibitory effect of a red cabbage seed extract on germination time, individual (single spore) and population lag time of Penicillium corylophilum was studied. First, to compare the biological variability of single spore germination and lag times under stressful conditions, data were collected at levels of red cabbage seed extract varying from 0 to 10mg/g (150 spores observed in each trial of germination, ca 50 spores in each individual lag experiment). Experiments were performed on malt agar at 25°C, pH5.2, aw 0.99. The data, without any transformation, were statistically analyzed; several probability distribution functions were used to fit the cumulated germination times and the individual lag times of spores. In both cases, the best fit was obtained with the Normal distribution. In parallel, lag times at the population level (ca 2000 spores per trial) were collected for the same range of plant extract. Not surprisingly, the difference between individual and population lag times could be explained by a stochastic process. More interestingly, it was shown that under stressful conditions, the population lag time did not correspond to the time required for germination of 95% of spores, but to a much longer time. Finally, it was deduced from the statistical analysis, completed by microscopic observations, that the plant extract affected mainly the hyphal elongation (and then the lag time) and not the germination. Next, secondary models were developed to quantify the effect of red cabbage seed extract on the median of germination times, individual and population lag times. The Minimum Inhibitory Concentrations (MICs) were estimated. It was shown that the red cabbage seed extract MIC for P. corylophilum lag time did not depend on the inoculum load. Application of the secondary models allowed us to conclude that under the conditions of our experiment, the addition of 10mg/g of red cabbage seed extract enabled extension of lag time to two weeks.


      PubDate: 2015-07-18T21:38:42Z
       
  • Is Cytotoxin K from Bacillus cereus a bona fide enterotoxin'
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Virginie Castiaux, Xiaojin Liu, Laurence Delbrassinne, Jacques Mahillon
      Cytotoxin K (CytK) produced by Bacillus cereus s.l. has generally been considered to be associated with the foodborne diarrhoeal syndrome. Two distinct variants of CytK have been reported: CytK-1 from Bacillus cytotoxicus and CytK-2 from B. cereus. In order to determine whether CytK plays a significant role in the diarrhoeal disease, the occurrence of cytK genes was assessed among 390 B. cereus isolates with different origins including clinical and food poisoning samples and was found to be 46%. Interestingly, the cytK occurrence was slightly lower in food poisoning and clinical isolates than in environmental samples. Seventy cytK-2 positive strains (including 28 isolates from foodborne outbreaks) were then selected in order to assess their genetic diversity. A genetic dendrogram based on the cytK-2 sequences of these 70 strains and on two cytK-1 sequences from strains NVH 391-98 and 883-00 showed an important diversity. However, no strain clustering according to the origin or source of isolation was observed. These observations were confirmed by Multi-Locus Sequences Typing (MLST) based on five different loci of housekeeping genes (ccpA, recF, sucC, purF and gdpD) for which no grouping of foodborne outbreak strains could be identified. Therefore, the choice of cytK as virulence factor for the diarrhoeal pathotype does not seem to be relevant per se, even though the involvement of CytK in the diarrhoeal syndrome cannot be fully excluded. Potential synergistic effects between CytK and other virulence factors, together with their potential variable expression levels should be further investigated.


      PubDate: 2015-07-18T21:38:42Z
       
  • Ultraviolet-C efficacy against a norovirus surrogate and hepatitis A virus
           on a stainless steel surface
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Shin Young Park , An-Na Kim , Ki-Hoon Lee , Sang-Do Ha
      In this study, the effects of 10–300mWs/cm2 of ultraviolet radiation (UV-C) at 260nm were investigated for the inactivation of two foodborne viruses: murine norovirus-1 (MNV-1; a human norovirus [NoV] surrogate) and hepatitis A virus (HAV). We used an experimentally contaminated stainless steel surface, a common food-contact surface, to examine the effects of low doses of UV-C radiation on MNV-1 and HAV titers. The modified Gompertz equation was used to generate non-linear survival curves and calculate dR-values as the UV-C dose of 90% reduction for MNV-1 (R2 =0.95, RMSE=0.038) and HAV (R2 =0.97, RMSE=0.016). Total MNV-1 and HAV titers significantly decreased (p<0.05) with higher doses of UV-C. MNV-1 and HAV were reduced to 0.0–4.4 and 0.0–2.6 log10PFU/ml, respectively, on the stainless steel surfaces by low-dose UV-C treatment. The dR-value, 33.3mWs/cm2 for MNV-1 was significantly (p<0.05) lower than 55.4mWs/cm2 of HAV. Therefore, the present study shows that HAV is more resistant to UV-C radiation than MNV-1. These data suggest that low doses of UV-C light on food contact surfaces could be effective to inactivate human NoV and HAV in restaurant, institutional, and industrial kitchens and facilities.


      PubDate: 2015-07-14T18:10:03Z
       
  • Application of a novel antimicrobial coating on roast beef for
           inactivation and inhibition of Listeria monocytogenes during storage
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Luxin Wang , Liang Zhao , Jing Yuan , Tony Z. Jin
      The antilisterial efficacy of novel coating solutions made with organic acids, lauric arginate ester, and chitosan was evaluated in a three-stage study on inoculated roast beef for the first time. Ready-to-eat roast beef was specially ordered from the manufacturer. The meat surface was inoculated with five-strain Listeria monocytogenes cocktail inoculums at two different levels, ~3 and 6LogCFU/cm2 and treated with the stock solution (HAMS), the 1:5 diluted solution (MAMS), and the 1:10 diluted solution (LAMS) (stage 1). During the 20min contact time, the antimicrobial coatings reduced the Listeria populations by approximately 0.9–0.3LogCFU/cm2. The higher the concentrations of the antimicrobial solution, the better the antilisterial effects were. The treated inoculated beef samples were then stored at 4°C for 30days. During storage, Listeria growth inhibition effects were seen. While no growth was seen from the HAMS-treated samples, a 1.6LogCFU/cm2 increase was seen for MAMS-treated samples, a 4.6LogCFU/cm2 increase was seen for LAMS-treated samples, and a 5.7LogCFU/cm2 increase was seen for NoAMS-treated samples on Day 30 (~3LogCFU/cm2 inoculation level). In the second stage, the impact of the roast beef storage time on solution's antilisterial effect was evaluated. Results showed that the effect of the antimicrobial solution was dependent on both the initial inoculation levels and storage times. In stage 3, the effect of the antimicrobial solution on roast beef quality was studied with both instrument measurement and sensory evaluation. Minor changes in color, pH, and water activity were found. However, only limited sensory differences were seen between the treated and untreated samples. When panels were able to accurately find color differences between samples, they preferred the treated samples. The findings of this research proved the antilisterial efficacy of the novel antimicrobial solution and showed its potential for being used as a roast beef cut surface coating to control Listeria contamination and for color protection.


      PubDate: 2015-07-14T18:10:03Z
       
  • Biodiversity of refrigerated raw milk microbiota and their enzymatic
           spoilage potential
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Mario von Neubeck , Claudia Baur , Manuel Krewinkel , Marina Stoeckel , Bertolt Kranz , Timo Stressler , Lutz Fischer , Jörg Hinrichs , Siegfried Scherer , Mareike Wenning
      The refrigerated storage of raw milk selects for psychrotolerant microorganisms, many of which produce peptidases and lipases. Some of these enzymes are heat resistant and are not sufficiently inactivated by pasteurisation or even ultra-high temperature (UHT) treatment. In the current study, 20 different raw cow's milk samples from single farms and dairy bulk tanks were analysed close to delivery to the dairies or close to processing in the dairy for their cultivable microbiota as well as the lipolytic and proteolytic potential of the isolated microorganisms. Altogether, 2906 isolates have been identified and assigned to 169 species and 61 genera. Pseudomonas, Lactococcus and Acinetobacter were the most abundant genera making up 62% of all isolates, whereas 46 genera had an abundance of <1% and represent only 6.6%. Of all isolates, 18% belong to hitherto unknown species, indicating that a large fraction of the milk microbiota is still unexplored. The potential of the isolates to produce lipases or peptidases followed in many cases a genus or group specific pattern. All isolates identified as members of the genus Pseudomonas exhibited mainly lipolytic and proteolytic activity or solely proteolytic activity. On the other hand, nearly all isolates of the genus Acinetobacter were lipolytic but not proteolytic. Only 37% of all tested lactic acid bacteria (LAB) showed enzymatic activity at 6°C and the type of activity was proteolytic in 97% of these cases.


      PubDate: 2015-07-14T18:10:03Z
       
  • Identification of integrons and phylogenetic groups of drug-resistant
           Escherichia coli from broiler carcasses in China
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Hao Wu , Shibo Xia , Fanyun Bu , Jing Qi , Yuqing Liu , Hai Xu
      The dissemination of drug-resistant Escherichia coli in poultry products is becoming a public concern, as it endangers food security and human health. It is very common for E. coli to exhibit drug resistance in the poultry industry in China due to the excessive use of antibiotics. However, few studies have examined the drug resistance endowed by integrons and integron-associated gene cassettes in different phylogenetic groups of E. coli isolated from broiler carcasses. In this study, 373 antibiotic-resistant E. coli strains were isolated from the surfaces or insides of broiler carcasses from a slaughterhouse in Shandong Province, China. According to phylogenetic assays of chuA, yjaA, and an anonymous DNA fragment, TSPE4-C2, these isolates belong to four phylogenetic groups (A, B1, B2, and D) and seven subgroups (A0, A1, B1, B21, B22, D1, and D2). Of the tested isolates, 95.71% (n=357) are multi-drug resistant, among which group B1 was predominant, accounting for 33.51% (n=125) of the tested isolates. A high percentage of the E. coli isolates were resistant to amoxicillin–clavulanic acid (99.20%, n=370), doxycycline (92.23%, n=344), sulfamethoxazole–trimethoprim (90.88%, n=339), ciprofloxacin, (64.61%, n=241), sulbactam–cefoperazone (51.21%, n=191), and amikacin (33.78%, n=126). Furthermore, among the 373 isolates, class 1 and 2 integrons were identified in 292 (78.28%) and 49 (13.14%) of the isolates, respectively, while no class 3 integrons were detected. The most prevalent gene cassette arrays were dfrA17–aadA5 and dfrA12–orfF–aadA2 in the variable region of class 1 integrons, while only one gene cassette array (dfrA1–sat2–aadA1) was detected in the variable region of class 2 integrons. Class 1 integrons were distributed in various physiological subtypes, whereas no predominant phylogenetic groups could be identified. The presence of class 2 integrons in the B21 subtype was significantly higher than in the other subtypes, and it coexisted with the class 1 integron. This study suggests that broiler products are potential sources of multi-drug resistant E. coli, and that resistance genes could be spread by lateral gene transfer.


      PubDate: 2015-07-14T18:10:03Z
       
  • 2,4-Di-tert-butyl phenol as the antifungal, antioxidant bioactive purified
           from a newly isolated Lactococcus sp.
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Kontham Kulangara Varsha , Leena Devendra , Ganesan Shilpa , Sulochana Priya , Ashok Pandey , Kesavan Madhavan Nampoothiri
      The volatile organic compound 2,4-di-tert-butyl phenol (2,4 DTBP) was purified from the cell free supernatant of a newly isolated Lactococcus sp. by solvent extraction and chromatographic techniques. Molecular characterization of the compound by ESI-MS, 1H NMR and FTIR analysis revealed the structure, C14H22O. Fungicidal activity was demonstrated against Aspergillus niger, Fusarium oxysporum and Penicillium chrysogenum by disc diffusion assay. Among the cell lines tested for cytotoxicity of this compound (normal cell line H9c2 and cancer cell lines HeLa and MCF-7), a remarkable cytotoxicity against HeLa cells with an IC50 value of 10μg/mL was shown. A biocontrol experiment with 2,4 DTBP supplemented fraction prevented growth of the abovementioned fungi on wheat grains. The study further strengthens the case for development of biopreservatives and dietary antioxidants from lactic acid bacteria for food applications.


      PubDate: 2015-07-09T17:52:41Z
       
  • Influence of general stress-response alternative sigma factors σS
           (RpoS) and σB (SigB) on bacterial tolerance to the essential oils
           from Origanum vulgare L. and Rosmarinus officinalis L. and pulsed electric
           fields
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Nelson Justino Gomes Neto , Marciane Magnani , Beatriz Chueca , Diego García-Gonzalo , Rafael Pagán , Evandro Leite de Souza
      This study assessed the influence of general stress-response alternative sigma factors RpoS (σS) and SigB (σB) on tolerance of Escherichia coli (E. coli MG1655 and its isogenic mutant E. coli MG1655 ΔrpoS) and Listeria monocytogenes (L. monocytogenes EGD-e and its isogenic mutant L. monocytogenes EGD-e ΔsigB) to the essential oils (EOs) from Origanum vulgare L.—oregano (OVEO) and Rosmarinus officinalis L.—rosemary (ROEO), as well as the changes in tolerance of parental and ΔrpoS and ΔsigB mutant strains to OVEO, ROEO and pulsed electric fields (PEF) following overnight exposure to subinhibitory concentrations (1/2×minimum inhibitory concentration—MIC) of each tested EO. MIC values of OVEO and ROEO against the mutant cells were usually lower than those found against the parental cells. Survivor curves showed that mutant cells were more sensitive to these EOs than parental cells. The recovery of survivors in selective media showed a greater proportion of cells sublethally injured at their cell envelopes in the mutant strains compared with the parental strains. Induction of increased direct-tolerance to OVEO and ROEO or cross-tolerance to PEF was not observed after pre-exposure of parental and mutant cells to EOs. Otherwise, parental and mutant cells of E. coli and L. monocytogenes pre-exposed to OVEO or ROEO showed decreased tolerance when further treated with the homologous stressing agent at 2×MIC. Still, mutant cells pre-exposed to OVEO or ROEO showed lower tolerance to PEF than parental strains. These results showed the influence of σS and σB in tolerance of single strains of E. coli and L. monocytogenes, respectively, to OVEO and ROEO. Moreover, the deletion of σS and σB resulted in decreased tolerance to OVEO, ROEO or PEF in tested strains following exposure to OVEO or ROEO at a subinhibitory concentration.


      PubDate: 2015-07-09T17:52:41Z
       
  • Stability, antimicrobial activity, and effect of nisin on the
           physico-chemical properties of fruit juices
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Adelson Alves de Oliveira Junior , Hyrla Grazielle Silva de Araújo Couto , Ana Andréa Teixeira Barbosa , Marcelo Augusto Guitierrez Carnelossi , Tatiana Rodrigues de Moura
      Heat processing is the most commonly used hurdle for inactivating microorganisms in fruit juices. However, this preservation method could interfere with the organoleptic characteristics of the product. Alternative methods have been proposed and bacteriocins such as nisin are potential candidates. However, the approval of bacteriocins as food additives is limited, especially in foods from vegetal origin. We aimed to verify the stability, the effect on physico-chemical properties, and the antimicrobial activity of nisin in different fruit juices. Nisin remained stable in fruit juices (cashew, soursop, peach, mango, passion fruit, orange, guava, and cupuassu) for at least 30days at room or refrigerated temperature and did not cause any significant alterations in the physico-chemical characteristics of the juices. Besides, nisin favored the preservation of vitamin C content in juices. The antimicrobial activity of nisin was tested against Alicyclobacillus acidoterrestris, Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes in cashew, soursop, peach, and mango juices. Nisin caused a 4-log reduction in viable cells of A. acidoterrestris in soursop, peach, and mango juices after 8h of incubation, and no viable cells were detected in cashew juices. After 24h of incubation in the presence of nisin, no viable cells were detected, independently of the juices. To S. aureus, at 24h of incubation in the presence of nisin, viable cells were only detected in mango juices, representing a 4-log decrease as compared with the control treatment. The number of viable cells of B. cereus at 24h of incubation in the presence of nisin represented at least a 4-log decrease compared to the control treatment. When the antimicrobial activity of nisin was tested against L. monocytogenes in cashew and soursop juices, no reduction in the viable cell number was observed compared to the control treatment after 24h of incubation. Viable cells were four and six times less than in the control treatment, in peach and mango juices respectively. The most sensitive microorganism to nisin was A. acidoterrestris and the least sensitive was L. monocytogenes. Still, a reduction of up to 90% of viable cells was observed in peach and mango juices inoculated with L. monocytogenes. These results indicate that the use of nisin could be an alternative in fruit juice processing.


      PubDate: 2015-07-09T17:52:41Z
       
  • Changes in flavour and microbial diversity during natural fermentation of
           suan-cai, a traditional food made in Northeast China
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Rina Wu , Meiling Yu , Xiaoyu Liu , Lingshuai Meng , Qianqian Wang , Yating Xue , Junrui Wu , Xiqing Yue
      We measured changes in the main physical and chemical properties, flavour compounds and microbial diversity in suan-cai during natural fermentation. The results showed that the pH and concentration of soluble protein initially decreased but were then maintained at a stable level; the concentration of nitrite increased in the initial fermentation stage and after reaching a peak it decreased significantly to a low level by the end of fermentation. Suan-cai was rich in 17 free amino acids. All of the free amino acids increased in concentration to different degrees, except histidine. Total free amino acids reached their highest levels in the mid-fermentation stage. The 17 volatile flavour components identified at the start of fermentation increased to 57 by the mid-fermentation stage; esters and aldehydes were in the greatest diversity and abundance, contributing most to the aroma of suan-cai. Bacteria were more abundant and diverse than fungi in suan-cai; 14 bacterial species were identified from the genera Leuconostoc, Bacillus, Pseudomonas and Lactobacillus. The predominant fungal species identified were Debaryomyces hansenii, Candida tropicalis and Penicillium expansum.


      PubDate: 2015-07-09T17:52:41Z
       
  • Characterization of specific alleles in InlA and PrfA of Listeria
           monocytogenes isolated from foods in Osaka, Japan and their ability to
           invade Caco-2 cells
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Masashi Kanki , Hisayo Naruse , Masumi Taguchi , Yuko Kumeda
      Listeria monocytogenes expresses the surface protein internalin A (InlA), enabling the invasion of human intestinal epithelial cells to cause severe food-borne diseases. Full-length sequence analysis of inlA of 114 food isolates resulted in the detection of 29 isolates with a premature stop codon (PMSC) mutation and 6 isolates with 3-codon deletion mutations (aa 738 to 740) in inlA. The isolates with inlA PMSCs demonstrated a significantly lower level of invasion than the other food isolates in a Caco-2 cell invasion assay (P <0.01), but the isolates with the 3-codon deletion exhibited invasion comparable to the isolates with non-truncated InlA (P >0.05). According to analysis of the positive regulatory factor A (PrfA) sequences of 114 L. monocytogenes isolates, 7 isolates of serotype 1/2a from chicken samples contained a PrfA protein with a 5-nucleotide deletion from 712 to 716, including a stop codon. Although the isolates with a 5-nucleotide deletion in prfA demonstrated invasion comparable to the isolates with non-truncated InlA and PrfA after growth at 30°C (P >0.05), they exhibited a significantly higher level of invasion than the other isolates after growth at 20°C (P <0.01). To the authors' knowledge, this is the first report of L. monocytogenes isolates with the stop-codon deletion of PrfA.


      PubDate: 2015-07-05T17:36:47Z
       
  • Biotransformation of aflatoxin B1 and aflatoxin G1 in peanut meal by
           anaerobic solid fermentation of Streptococcus thermophilus and
           Lactobacillus delbrueckii subsp. bulgaricus
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Yujie Chen , Qing Kong , Chen Chi , Shihua Shan , Bin Guan
      The purpose of this study was to explore the ability of anaerobic solid fermentation of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus to biotransform aflatoxins in peanut meal. The pH of the peanut meal was adjusted above 10, and then heated for 10min at 100°C, 115°C and 121°C. The S. thermophilus and L. delbrueckii subsp. bulgaricus were precultured together in MRS broth for 48h at 37°C. The heated peanut meal was mixed with precultured MRS broth containing 7.0×108 CFU/mL of S. thermophilus and 3.0×103 CFU/mL of L. delbrueckii subsp. bulgaricus with the ratio of 1 to 1 (weight to volume) and incubated in anaerobic jars at 37°C for 3days. The aflatoxin content in the peanut meal samples was determined by HPLC. The results showed that the peanut meal contained mainly aflatoxin B1 (AFB1) (10.5±0.64μg/kg) and aflatoxin G1 (AFG1) (18.7±0.55μg/kg). When heat treatment was combined with anaerobic solid fermentation, the biotransformation rate of aflatoxins in peanut meal could attain 100%. The cytotoxicity of fermented peanut meal to L929 mouse connective tissue fibroblast cells was determined by MTT assay and no significant toxicity was observed in the fermented peanut meal. Furthermore, heat treatment and anaerobic solid fermentation did not change the amino acid concentrations and profile in peanut meal.


      PubDate: 2015-07-05T17:36:47Z
       
  • Added value of experts' knowledge to improve a quantitative microbial
           exposure assessment model — Application to aseptic-UHT food products
           
    • Abstract: Publication date: 15 October 2015
      Source:International Journal of Food Microbiology, Volume 211
      Author(s): Laure Pujol , Nicholas Brian Johnson , Catherine Magras , Isabelle Albert , Jeanne-Marie Membré
      In a previous study, a quantitative microbial exposure assessment (QMEA) model applied to an aseptic-UHT food process was developed [Pujol, L., Albert, I., Magras, C., Johnson, N. B., Membré, J. M. Probabilistic exposure assessment model to estimate aseptic UHT product failure rate. 2015 International Journal of Food Microbiology. 192, 124–141]. It quantified Sterility Failure Rate (SFR) associated with Bacillus cereus and Geobacillus stearothermophilus per process module (nine modules in total from raw material reception to end-product storage). Previously, the probabilistic model inputs were set by experts (using knowledge and in-house data). However, only the variability dimension was taken into account. The model was then improved using expert elicitation knowledge in two ways. First, the model was refined by adding the uncertainty dimension to the probabilistic inputs, enabling to set a second order Monte Carlo analysis. The eight following inputs, and their impact on SFR, are presented in detail in this present study: D-value for each bacteria of interest (B. cereus and G. stearothermophilus) associated with the inactivation model for the UHT treatment step, i.e., two inputs; log reduction (decimal reduction) number associated with the inactivation model for the packaging sterilization step for each bacterium and each part of the packaging (product container and sealing component), i.e., four inputs; and bacterial spore air load of the aseptic tank and the filler cabinet rooms, i.e., two inputs. Second, the model was improved by leveraging expert knowledge to develop further the existing model. The proportion of bacteria in the product which settled on surface of pipes (between the UHT treatment and the aseptic tank on one hand, and between the aseptic tank and the filler cabinet on the other hand) leading to a possible biofilm formation for each bacterium, was better characterized. It was modeled as a function of the hygienic design level of the aseptic-UHT line: the experts provided the model structure and most of the model parameters values. Mean of SFR was estimated to 10×10−8 (95% Confidence Interval=[0×10−8; 350×10−8]) and 570×10−8 (95% CI=[380×10−8; 820×10−8]) for B. cereus and G. stearothermophilus, respectively. These estimations were more accurate (since the confidence interval was provided) than those given by the model with only variability (for which the estimates were 15×10−8 and 580×10−8 for B. cereus and G. stearothermophilus, respectively). The updated model outputs were also compared with those obtained when inputs were described by a generic distribution, without specific information related to the case-study. Results showed that using a generic distribution can lead to unrealistic estimations (e.g., 3,181,000 product units contaminated by G. stearothermophilus among 108 product units produced) and emphasized the added value of eliciting information from experts from the relevant specialist field knowledge.


      PubDate: 2015-07-05T17:36:47Z
       
  • Investigation of the protective effect of whey proteins on lactococcal
           phages during heat treatment at various pH
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Hany Geagea , Ahmed I. Gomaa , Gabriel Remondetto , Sylvain Moineau , Muriel Subirade
      The incorporation of whey protein concentrates (WPC) into cheese is a risky process due to the potential contamination with thermo-resistant phages of lactic acid bacteria (LAB). Furthermore, whey proteins can protect phages during heat treatment, thereby increasing the above risk. The main objective of this work was to understand this protective effect in order to better control LAB phages and maximize whey recycling in the cheese industry. First, the inactivation of a previously characterized thermo-resistant lactococcal virulent phage (P1532) was investigated at 95°C in WPC, in individual whey components β-lactoglobulin, α-lactalbumin, and bovine serum albumin as well as under different heat and pH conditions. The structural changes of the tested proteins were also monitored by transmission FTIR spectroscopy. Phage inactivation results indicated that the protective effect of whey proteins was pH and time dependent at 95°C and was not restricted to one component. FTIR spectra suggest that the protection is related to protein molecular structures and to the level of protein aggregates, which was more pronounced in acidic conditions. Moreover, the molecular structure of the three proteins tested was differently influenced by pH and the duration of the heat treatment. This work confirms the protective effect of WPC on phages during heat treatment and offers the first hint to explain such phenomenon. Finding the appropriate treatment of WPC to reduce the phage risk is one of the keys to improving the cheese manufacturing process.


      PubDate: 2015-07-01T17:31:31Z
       
  • Comparative analysis of antimicrobial resistance and genetic diversity of
           Campylobacter from broilers slaughtered in Poland
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Kinga Wieczorek , Edyta Denis , Jacek Osek
      In the current study, the relationship of Campylobacter jejuni and Campylobacter coli strains isolated at slaughter was investigated using comparative analysis of antimicrobial resistance (AMR), virulence gene (VG) and PFGE profiling. A total of 254 Campylobacter isolates from poultry caeca and corresponding carcasses, including 139 C. jejuni and 115 C. coli strains were tested. The most prevalent resistance profiles observed in C. jejuni were ciprofloxacin, nalidixic acid and tetracycline (46 out of 139, 33.1% isolates) as well as ciprofloxacin, nalidixic acid, tetracycline and streptomycin among C. coli strains (34 out of 115, 29.6%). Multi-resistance was found more frequently among C. coli than C. jejuni (P <0.05). The presence of 11 virulence genes exhibited 19 different VG profiles in Campylobacter isolates tested. All Campylobacter strains were classified into 154 different PFGE types. Among them, 56 profiles (28 C. jejuni and 28 C. coli) were common for at least two isolates including 9 clusters covering from 4 to 9 strains. Campylobacter composite types generated by a combination of 154 PFGE types, 10 AMR profiles and 19 VG patterns divided 178 distinct types with 95% similarity. The majority of the composite profiles (76 for C. jejuni and 58 for C. coli; 75.3% in total) included only one bacterial isolate. Furthermore, 11 pairs of C. jejuni and 12 pairs of C. coli from caeca and the corresponding carcasses isolated from the same places possessed the identical PFGE, AMR and VG patterns. This study demonstrated that C. jejuni and C. coli isolated from poultry in Poland showed to have a high genetic diversity and a weak clonal population structure. However, the composite analysis revealed a strong evidence for cross-contamination of chicken carcasses during the slaughter process. Additionally, our results confirm that Campylobacter may easily contaminate poultry carcasses at slaughter process and spread around country. More than half of Campylobacter strains tested (50.4%) were resistant to at least two classes of antimicrobials, i.e. quinolones and tetracyclines, which may cause a public health risk.


      PubDate: 2015-07-01T17:31:31Z
       
  • Phenotypic and genotypic characterization of lactic acid bacteria isolated
           from raw goat milk and effect of farming practices on the dominant species
           of lactic acid bacteria
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Hélène Tormo , Djamila Ali Haimoud Lekhal , C. Roques
      Lactic acid bacteria, in particular Lactococcus lactis, play a decisive role in the cheese making process and more particularly in lactic cheeses which are primarily produced on goat dairy farms. The objective of this study was therefore to identify the main lactic acid bacteria found in raw goats' milk from three different regions in France and evaluate if certain farming practices have an effect on the distribution of species of lactic acid bacteria in the various milk samples. Identification at genus or species level was carried out using phenotypic tests and genotypic methods including repetitive element REP-PCR, species-specific PCR and 16S rRNA gene sequencing. The distribution of the main bacterial species in the milk samples varied depending on farms and their characteristics. Out of the 146 strains identified, L. lactis was the dominant species (60% of strains), followed by Enterococcus (38%) of which Enterococcus faecalis and Enterococcus faecium. Within the species L. lactis, L. lactis subsp lactis was detected more frequently than L. lactis subsp cremoris (74% vs. 26%). The predominance of L. lactis subsp cremoris was linked to geographical area studied. It appears that the animals' environment plays a role in the balance between the dominance of L. lactis and enterococci in raw goats' milk. The separation between the milking parlor and the goat shed (vs no separation) and only straw in the bedding (vs straw and hay) seems to promote L. lactis in the milk (vs enterococci).


      PubDate: 2015-07-01T17:31:31Z
       
  • Development of an FgMito assay: A highly sensitive mitochondrial based
           qPCR assay for quantification of Fusarium graminearum sensu stricto
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Tomasz Kulik , Anna Ostrowska , Maciej Buśko , Matias Pasquali , Marco Beyer , Sebastian Stenglein , Dariusz Załuski , Jakub Sawicki , Kinga Treder , Juliusz Perkowski
      An ascomycete fungus, Fusarium graminearum sensu stricto (s.s.), is the major cause of Fusarium head blight (FHB), a devastating disease of cereals worldwide. The fungus contaminates crops with mycotoxins, which pose a serious threat to food and feed safety. In this study, we developed a highly sensitive mitochondrial based qPCR assay (FgMito qPCR) for quantification of F. graminearum s.s. To ensure high sensitivity of the assay, primers and a Minor-groove binding (MGB) probe were designed based on multi-copy mitochondrial DNA. The FgMito assay was successfully validated against a range of geographically diverse F. graminearum s.s. strains to ensure uniformity of the assay at an intraspecific level, as well as with other fungal species to ensure specificity. The assay was further evaluated in terms of efficiency and sensitivity against a test panel of different F. graminearum s.s. strains with various levels of pure fungal DNA and in the presence of wheat background DNA. The results showed a high efficiency of the assay developed, ranging from 93% to 101% with r 2-values of >0.99. We further showed that three low concentrations of fungal template 2pg, 0.6pg and 0.2pg could be reliably quantified in the presence of wheat background DNA. The FgMito assay was used to quantify F. graminearum s.s. DNA on 65 field samples from a range of hosts with defined levels of trichothecenes. We revealed a significant positive correlation between fungal DNA quantity and the sum of trichothecenes. Lastly, we showed a higher sensitivity of the FgMito assay than the nuclear based qPCR assay for F. graminearum s.s. by comparing Ct-values from both assays.


      PubDate: 2015-07-01T17:31:31Z
       
  • Cold plasma inactivation of internalised bacteria and biofilms for
           Salmonella enterica serovar Typhimurium, Listeria monocytogenes and
           Escherichia coli
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Dana Ziuzina , Lu Han , Patrick J. Cullen , Paula Bourke
      Microbial biofilms and bacteria internalised in produce tissue may reduce the effectiveness of decontamination methods. In this study, the inactivation efficacy of in-package atmospheric cold plasma (ACP) afterglow was investigated against Salmonella Typhimurium, Listeria monocytogenes and Escherichia coli in the forms of planktonic cultures, biofilms formed on lettuce and associated bacteria internalised in lettuce tissue. Prepared lettuce broth (3%) was inoculated with bacteria resulting in a final concentration of ~7.0log10 CFU/ml. For biofilm formation and internalisation, lettuce pieces (5×5cm) were dip-inoculated in bacterial suspension of ~7.0log10 CFU/ml for 2h and further incubated for 0, 24 and 48h at either 4°C or room temperature (~22°C) in combination with light/dark photoperiod or at 4°C under dark conditions. Inoculated samples were sealed inside a rigid polypropylene container and indirectly exposed (i.e. placed outside plasma discharge) to a high voltage (80kVRMS) air ACP with subsequent storage for 24h at 4°C. ACP treatment for 30s reduced planktonic populations of Salmonella, L. monocytogenes and E. coli suspended in lettuce broth to undetectable levels. Depending on storage conditions, bacterial type and age of biofilm, 300s of treatment resulted in reduction of biofilm populations on lettuce by a maximum of 5log10 CFU/sample. Scanning electron and confocal laser microscopy pointed to the incidence of bacterial internalisation and biofilm formation, which influenced the inactivation efficacy of ACP. Measured intracellular reactive oxygen species (ROS) revealed that the presence of organic matter in the bacterial suspension might present a protective effect against the action of ROS on bacterial cells. This study demonstrated that high voltage in-package ACP could be a potential technology to overcome bacterial challenges associated with food produce. However, the existence of biofilms and internalised bacteria should be considered for further optimisation of ACP treatment parameters in order to achieve an effective control of the realistic challenges posed by foodborne pathogens.


      PubDate: 2015-07-01T17:31:31Z
       
  • Cracking Streptococcus thermophilus to stimulate the growth of the
           probiotic Lactobacillus casei in co-culture
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Chengjie Ma , Aimin Ma , Guangyu Gong , Zhenmin Liu , Zhengjun Wu , Benheng Guo , Zhengjun Chen
      Lactobacillus casei, a probiotic, and Streptococcus thermophilus, a fast acidifying lactic acid bacterial strain, are both used in the food industry. The aim of this study was to investigate the interaction between L. casei and S. thermophilus in the presence or absence of S. thermophilus-specific bacteriophage during milk fermentation. The acidification capability of L. casei co-cultured with S. thermophilus was significantly higher than that observed for L. casei or S. thermophilus cultured alone. However, the probiotic content (i.e., L. casei cell viability) was low. The fastest acidification and the highest viable L. casei cell count were observed in co-cultures of L. casei and S. thermophilus with S. thermophilus phage. In these co-cultures, S. thermophilus compensated for the slow acid production of L. casei in the early exponential growth phase. Thereafter, phage-induced lysis of the S. thermophilus cells eliminated the competition for nutrients, allowing L. casei to grow well. Additionally, the ruptured S. thermophilus cells released intracellular factors, which further promoted the growth and function of the probiotic bacteria. Crude cellular extract isolated from S. thermophilus also significantly accelerated the growth and propagation of L. casei, supporting the stimulatory role of the phage on this micro-ecosystem.


      PubDate: 2015-07-01T17:31:31Z
       
  • Prevalence of antimicrobial resistance of non-typhoidal Salmonella
           serovars in retail aquaculture products
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Jianmin Zhang , Xiaowei Yang , Dai Kuang , Xianming Shi , Wenjia Xiao , Jing Zhang , Zhen Gu , Xuebin Xu , Jianghong Meng
      Aquaculture products can become sources of Salmonella by exposure to contaminated water or through processing practices, thus representing a public health hazard. A study was conducted on Salmonella contamination in aquaculture products sampled from marketplaces and retailers in Shanghai, China. A total of 730 samples (including fish, shellfish, bullfrog, clam, shrimp and others) were obtained from 2006 to 2011. Among them, 217 (29.7%) were positive for Salmonella. Thirty-eight serovars were identified in the 217 Salmonella isolates. The most prevalent were Salmonella Aberdeen (18.4%), S. Wandsworth (12.0%), S. Thompson (9.2%), S. Singapore (5.5%), S. Stanley (4.6%), S. Schwarzengrund (4.6%), S. Hvittingfoss (4.1%) and S. Typhimurium (4.1%). Many resistant isolates were detected, with 69.6% resistant to at least one antimicrobial drug. We observed high resistance to sulfonamides (56.5%), tetracycline (34.1%), streptomycin (28.6%), ampicillin (23.5%) and nalidixic acid (21.2%). Lower levels of resistance were found for gentamicin (3.2%), ciprofloxacin (2.3%), ceftiofur (1.3%), cefotaxime (0.9%), ceftazidime (0.5%) and cefepime (0.5%). A total of 43.3% of the Salmonella isolates were multidrug-resistant and 44 different resistance patterns were found. This study provided data on the prevalence, serovars and antimicrobial resistance of Salmonella from retail aquaculture products in Shanghai, and indicated the need for monitoring programs for microbiologic safety in such projects and for more prudent drug use in aquaculture production in order to reduce the risk of development and spread of antimicrobial resistance.


      PubDate: 2015-07-01T17:31:31Z
       
  • Antimicrobial activity of thyme oil co-nanoemulsified with sodium
           caseinate and lecithin
    • Abstract: Publication date: 1 October 2015
      Source:International Journal of Food Microbiology, Volume 210
      Author(s): Jia Xue , P. Michael Davidson , Qixin Zhong
      Emulsions of essential oils are investigated as potential intervention strategies to improve food safety and are preferably prepared from generally-recognized-as-safe emulsifiers. Stable thyme oil nanoemulsions can be prepared using combinations of sodium caseinate (NaCas) and soy lecithin. The objective of the present research was to study the antimicrobial activity of these nanoemulsions and understand the impacts of emulsifier concentrations. 10g/L thyme oil was emulsified using combinations of (A) 4% w/v NaCas and 0.5% w/v lecithin or (B) 2% w/v NaCas and 0.25% w/v lecithin by high shear homogenization. Combination A resulted in a transparent emulsion with a mean droplet diameter of 82.5nm, while it was turbid for the Combination B with an average diameter of 125.5nm. Nanoemulsified thyme oil exhibited quicker initial reductions of bacteria than free thyme oil in tryptic soy broth (TSB) and 2% reduced fat milk at 21°C, due to the improved dispersibility of thyme oil. In TSB with 0.3g/L thyme oil, it took less than 4 and 8h for two nanoemulsions and free oil, respectively, to reduce Escherichia coli O157:H7 and Listeria monocytogenes to be below the detection limit. The emulsified thyme oil also demonstrated more significant reductions of bacteria initially (4 and 8h) in 2% reduced fat milk than free thyme oil. Especially, with 4g/L thyme oil, the nanoemulsion prepared with Combination A reduced L. monocytogenes to be below the detection limit after 72h, while the free thyme oil treatment was only bacteriostatic and the turbid nanoemulsion treatment with Combination B resulted in about 1logCFU/mL reduction. However, E. coli O157:H7 treated with 3g/L emulsified thyme oil and Salmonella Enteritidis treated with 4g/L emulsified thyme oil recovered to a higher extent in milk than free thyme oil treatments. The increased concentration of emulsifiers in Combination A apparently reduced the antimicrobials available to alter bacteria membrane permeability as tested by the crystal violet assay at low antimicrobial concentrations and short time (1h). The findings suggest that nanoemulsions can be potentially used to incorporate thyme oil for use as antimicrobial preservatives in foods.


      PubDate: 2015-07-01T17:31:31Z
       
 
 
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