Extreme thermal resistance of dairy bacteriophages requires an update of traditional phage detection methodologies

NEVE HORST ; CAPRA MARÍA LUJÁN; SORATI PAMELA C.; ATAMER ZEYNEP; HINRICHS JÖRG; HELLER KNUT; QUIBERONI ANDREA

Stuttgart

Conferencia; Dairy Conference 2013; 2013

GfM Gesellschaft für Milchwissenschaft - Society of Milk Science,

Starter culture failures due to bacteriophage attacks reduce product quality and maycause financial losses. Phage monitoring is important to the dairy industry foridentifying contamination sources in the plant and for assessing contamination levels.Hence, countermeasures can be initiated rapidly in case of severe phage infections.Standard microbiological methods are still crucial to detect phages as they allow theidentification of active phage particles. Several dairy phages isolated in the last yearsexhibited extraordinary high thermal resistances. It was the aim of this work torevise and update the standard IDF microbiological methodology for phage detectionwhich includes a mandatory control treated for 15 min at 90°C for discrimination ofphage- and non-phage inhibitors. This standard is, however, obsolete, sincesurvivors of heat-stable phage populations will give false results. Phages specific forLactococcus lactis, Streptococcus thermophilus, Lactobacillus casei and Lb.paracasei were investigated to establish a reliable heat-treatment for the processingof industrial dairy samples suspected to contain phages. A prolonged heating-stepof 45 min at 90ºC is proposed.