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Kim Y.,Chonbuk National University | Lee J.W.,Chonnam National University | Kang S.-G.,Chonnam National University | Oh S.,Chonnam National University | Griffiths M.W.,Canadian Research Institute for Food Safety

The effect of Bifidobacterium spp. on the production of quorum-sensing (QS) signals and biofilm formation by enterohemorrhagic Escherichia coli (EHEC) O157:H7 was investigated. In an AI-2 bioassay, cell extracts of Bifidobacterium longum ATCC 15707 resulted in a 98-fold reduction in AI-2 activity in EHEC O157:H7 as well as in the Vibrio harveyi reporter strain, even though they did not inhibit the growth of EHEC O157:H7. In addition, they resulted in a 36% reduction in biofilm formation by the organism. Consistently, the virulence of EHEC O157:H7 was significantly attenuated by the presence of cell extracts of B. longum ATCC 15707 in the Caenorhabditis elegans nematode in vivo model. By a proteome analysis using two dimensional electrophoresis (2-DE), we determined that seven proteins including formation of iron-sulfur protein (NifU), thiol:disulfide interchange protein (DsbA), and flagellar P-ring protein (FlgI) were differentially regulated in the EHEC O157:H7 when supplemented with cell extracts of B. longum ATCC 15707. Taken together, these findings propose a novel function of a dairy adjunct in repressing the virulence of EHEC O157:H7. © 2012. Source

Wang J.,South China Agricultural University | Wang J.,Agriculture and Agri Food Canada | Niu Y.D.,Alberta Agriculture and Rural Development | Chen J.,South China Agricultural University | And 7 more authors.
Canadian Journal of Microbiology

This study aimed to isolate and characterize bacteriophages that lyse non-O157 Shiga toxin-producing Escherichia coli (STEC) from cattle feces. Of 37 non-O157 STEC-infecting phages isolated, those targeting O26 (AXO26A, AYO26A, AYO26B), O103 (AXO103A, AYO103A), O111 (AXO111A, AYO111A), O121 (AXO121A, AXO121B), and O145 (AYO145A, AYO145B) were further charac-terized. Transmission electron microscopy showed that the 11 isolates belonged to 3 families and 6 genera: the families Myoviridae (types rV5, T4, ViI, O1), Siphoviridae (type T5), and Podoviridae (type T7). Genome size of the phages as determined by pulsed-field gel electrophoresis ranged from 38 to 177 kb. Excluding phages AXO26A, AYO103A, AYO145A, and AYO145B, all other phages were capable of lysing more than 1 clinically important strain from serogroups of O26, O91, O103, O111, O113, O121, and O128, but none exhibited infectivity across all serogroups. Moreover, phages AYO26A, AXO121A, and AXO121B were also able to lyse 4 common phage types of STEC O157:H7. Our findings show that a diversity of non-O157 STEC-infecting phages are harbored in bovine feces. Phages AYO26A, AYO26B, AXO103A, AXO111A, AYO111A, AXO121A, and AXO121B exhibited a broad host range against a number of serogroups of STEC and have potential for the biocontrol of STEC in the environment. Source

Mundi A.,University of Guelph | Delcenserie V.,University of Guelph | Delcenserie V.,Canadian Research Institute for Food Safety | Amiri-Jami M.,University of Guelph | And 4 more authors.
Journal of Food Protection

Campylobacter spp. are among the most commonly reported bacterial causes of acute diarrheal disease in humans worldwide. Potential virulence factors include motility, chemotaxis, colonization ability, adhesion to intestinal cells, invasion and epithelial translocation, intracellular survival, and formation of toxins. Probiotic Lactobacillus and Bifidobacterium strains are known to have an inhibitory effect against the growth of various foodborne pathogens. The objective of this study was to investigate the effect of Lactobacillus acidophilus strain La-5 and Bifidobacterium longum strain NCC2705 cell-free spent media (CFSM) on the expression of virulence genes (cadF, cdtB, flaA, and ciaB) of Campylobacter jejuni strain 81-176 and a luxS mutant, using real-time PCR. Our results demonstrated that the CFSM of both probiotic strains were able to down-regulate the expression of ciaB (ratio of -2.80 and -5.51, respectively) and flaA (ratio of -7.00 and -5.13, respectively) in the wild-type Campylobacter strain. In the luxS mutant, where the activated methyl cycle is disrupted, only the ciaB gene (ratio -7.21) was repressed in the presence of La-5 CFSM. A supplementation of homocysteine to restore the disrupted cycle was able to partially reestablish the probiotic effect of both strains. luxS and the activated methyl cycle might play an active role in the modulation of virulence of C. jejuni by probiotic extracts. Copyright © International Association for Food Protection. Source

Morales-Rayas R.,University of Guelph | Morales-Rayas R.,Canadian Research Institute for Food Safety | Wolffs P.F.G.,Maastricht University | Griffiths M.W.,University of Guelph | Griffiths M.W.,Canadian Research Institute for Food Safety
International Journal of Food Microbiology

Two sample preparation methods based on electrostatic binding were tested to simultaneously separate different viral particles from different food surfaces (lettuce, strawberry, raspberries and green onions). Both methods were evaluated using a multiplex real-time PCR assay designed for detection of hepatitis A virus and norovirus GI and GII. Single and multiplex detection limits were determined as 101 viral particles for HAV and norovirus GII, and 102 viral particles for norovirus GI using artificial templates, one HAV strain and different norovirus isolates. Manual extraction based on silica columns was found more suitable for viral RNA preparation than an automatic extraction technique. Consistent detection of infectious amounts (2-20viral particles/g) of HAV and norovirus in different food samples was achievable when the viruses were concentrated using cationically charged filters rather than with cationically charged beads in a flow-through system. Consequently, the developed multiplex detection protocol provides a promising alternative for rapid and simultaneous detection of viral pathogens in foods. © 2010 Elsevier B.V. Source

Liu G.,China Agricultural University | Liu G.,University of Guelph | Liu G.,Canadian Research Institute for Food Safety | Griffiths M.W.,University of Guelph | And 4 more authors.
Journal of Food Protection

The technological feasibility of producing fermented sausages using the bacteriocin-producing Lactobacillus pentosus 31-1. isolated from a traditional Chinese fermented meat product (Xuanwei ham), was evaluated. Strain 31-1 was used both as a single starter and in coculture for manufacture of fermented sausages. The microbiological and physicochcmical properties (color, texture, and sensory quality) and the production of bacteriocin during ripening of these products were compared with those characteristics of sausages produced with a commercial meat starter. Challenge tests were performed using Listeria innocua or Staphylococcus aureus as target strains. The addition of L. pentosus 31-1 can significantly reduce L. innocua and S. aureus populations during all ripening phases. Free amino acid and free fatty acid analysis suggested that strain 31-1 might have proteolytic and lipolytic activity. The use of this strain resulted in a final product with a brighter surface and better texture and sensory profiles. A maximum bacteriocin (pentocin 31-1 ) concentration of 640 AU/g was detected in homogenized sausages with added L. pentosus 31 -1, The bacteriocin-producing strain L. pentosus 31-1 could be used as a novel functional starter culture or coculture for sausage fermentation. Copyright ©, International Association for Food Protection. Source

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