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Personne :
St-Gelais, Daniel

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St-Gelais

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Daniel

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Université Laval. Département des sciences des aliments

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ncf10190340

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  • PublicationAccès libre
    Improving the safety of Staphylococcus aureus polyvalent phages by their production on a Staphylococcus xylosus strain
    (Public Library of Science, 2014-07-25) Dumaresq, Jeannot; Labrie, Steve; Moineau, Sylvain; Plante, Pier-Luc; Katsarava, Ramaz; El Haddad, Lynn; St-Gelais, Daniel; Ben Abdallah, Nour
    Team1 (vB_SauM_Team1) is a polyvalent staphylococcal phage belonging to the Myoviridae family. Phage Team1 was propagated on a Staphylococcus aureus strain and a non-pathogenic Staphylococcus xylosus strain used in industrial meat fermentation. The two Team1 preparations were compared with respect to their microbiological and genomic properties. The burst sizes, latent periods, and host ranges of the two derivatives were identical as were their genome sequences. Phage Team1 has 140,903 bp of double stranded DNA encoding for 217 open reading frames and 4 tRNAs. Comparative genomic analysis revealed similarities to staphylococcal phages ISP (97%) and G1 (97%). The host range of Team1 was compared to the well-known polyvalent staphylococcal phages phi812 and K using a panel of 57 S. aureus strains collected from various sources. These bacterial strains were found to represent 18 sequence types (MLST) and 14 clonal complexes (eBURST). Altogether, the three phages propagated on S. xylosus lysed 52 out of 57 distinct strains of S. aureus. The identification of phage-insensitive strains underlines the importance of designing phage cocktails with broadly varying and overlapping host ranges. Taken altogether, our study suggests that some staphylococcal phages can be propagated on food-grade bacteria for biocontrol and safety purposes.
  • PublicationRestreint
    Efficacy of two Staphylococcus aureus phage cocktails in cheese production
    (Elsevier Science Publishers, 2015-10-05) Labrie, Steve; Roy, Jean-Pierre; Moineau, Sylvain; Khalil, Georges E.; Champagne, Claude P.; El Haddad, Lynn; St-Gelais, Daniel
    Staphylococcus aureus is one of the most prevalent pathogenic bacteria contaminating dairy products. In an effort to reduce food safety risks, virulent phages are investigated as antibacterial agents to control foodborne pathogens. The aim of this study was to compare sets of virulent phages, design phage cocktails, and use them in a cocktail to control pathogenic staphylococci in cheese. Six selected phages belonging to the three Caudovirales families (Myoviridae, Siphoviridae, Podoviridae) were strictly lytic, had a broad host range, and did not carry genes coding for virulence traits in their genomes. However, they were sensitive to pasteurization. At MOI levels of 15, 45, and 150, two anti-S. aureus phage cocktails, each containing three phages, one from each of the three phage families, eradicated a 106 CFU/g S. aureus population after 14 days of Cheddar cheese curd ripening at 4 °C. The use of these phages did not trigger over-production of S. aureus enterotoxin C. The use of phage cocktails and their rotation may prevent the emergence of phage resistant bacterial strains.