Diversity of Streptococcus thermophilus phages in a large production cheese factory in argentina (Póster)

QUIBERONI, A.; TREMBLAY, D.; ACKERMANN, H.; REINHEIMER, J.; MOINEAU, S.

Buenos Aires (Argentina)

Congreso; III Congreso Argentino de Microbiología de Alimentos; 2006

Asociación Argentina de Microbiología - DAMyC

Phage infections still represent a serious risk to the dairy industry where Streptococcus thermophilus is used in starter cultures for the manufacture of yogurt and cheeses. S. thermophilus strains are predominantly found in starter cultures used for Argentinean fermented milks and several varieties of soft and semi hard cheeses (Cremoso, Cuartirolo, Por Salut, Holanda, Fontina, Colonia, Edam and Pategrás). Thus, it is considered the most technologically important lactic acid bacteria by the dairy industry in Argentina. Unfortunately, several S. thermophilus strains used in commercial starters are highly sensitive to phages. To our knowledge, the biodiversity of Argentinean S. thermophilus phages isolated from cheese plants has never been investigated. Therefore, the aim of this work was to determine the phage diversity in one cheese plant environment using morphological and genetic criteria. Ten S. thermophilus distinct phages were isolated from a total of 14-cheese whey samples collected in a 2-month survey. Then, they were characterized by their morphology, host range, and the restriction patterns (EcoRV and EcoRI) of their double-stranded genome. These phages were also classified within the two main groups of S. thermophilus phages (cos- and pac-type) using a newly adapted multiplex PCR method. All phages were members of the Siphoviridae family and of the B1 morphotype, showing non-contractile tails slightly longer (approx. 300 nm) than previously reported (230-260 nm). Using the multiplex PCR method, six phages were classified as cos-type phages while the four others belong to the pac-type group. Results of this study reflect the phage diversity found in a single cheese plant with a considerable rotation of commercial cultures of S. thermophilus. Consequently, limiting the number of starter cultures is likely to reduce the phage biodiversity within a fermentation facility. Our findings that Argentinean S. thermophilus phages could be classified within the two known phage groups, complement the previous phage epidemiology data from European countries. A detailed knowledge of the genetic diversity of S. thermophilus phages as well as a regular monitoring of the phage population within an industrial environment are essential for the successful application of phage control measures and for the development of adapted anti-phage strategies.