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Aims: To examine whether pulsed-field gel electrophoresis (PFGE) of DNA macro-restriction fragments could provide better discrimination among the different biotypes previously described within the species Staphylococcus aureus than the traditional biochemical approach. Methods and Results: Seventy three Staph. aureus strains from various sources (human, animal or food origin) and belonging to eight biotypes, including the poultry-like biotype, tentatively designated as an ÔabattoirÕ biotype, were genotyped by PFGE after SmaI digestion of DNA. The PFGE patterns were compared using the average linkage matching method (UPGMA) with the Dice coefficient. A total of 61 PFGE patterns were observed, showing between 31 and 100% similarity. In most cases, strains with the same biotype were grouped specifically into one, two or three separate sub-clusters. Strains from the ÔabattoirÕ biotype were clustered in one separate sub-cluster. Conclusions: The PFGE typing is useful to distinguish the traditional biotypes of Staph. aureus and has a more discriminatory power than the biochemical typing. Significance and Impact of the Study: The PFGE typing confirms the ÔabattoirÕ biotype as a separate group on a genetic level and is well suited to investigate modes of staphylococcal contamination of food.

Aim:  Immunological tools used to detect staphylococcal enterotoxins (SEs) in foods are numerous. The aim of this study was to evaluate, on naturally contaminated milk product samples, the performance of the Vidas SET2, in comparison to the Transia plate SET. Methods and Results:  The Vidas SET2 was compared with the Transia plate SET on supernatants of Staphylococcus aureus isolates and on naturally contaminated milk products. It is noteworthy that when using IgG rabbit treatment, both kits can be considered as equivalent to detect enterotoxins in naturally contaminated milk products. Conclusions:  This study demonstrated that the Vidas SET2 performance is similar to that of Transia plate SET kit, when a rabbit IgG treatment step is used before detection step. This additional treatment significantly decreased, from 42% to 8%, the rate of positive deviations observed using the Transia plate SET detection kit. Significance and Impact of the Study:  The Vidas SET2 was clearly found as more specific, when no preliminary rabbit IgG treatment was used, and which results in a better workflow when a large number of samples have to be analysed within a few days. Considering the results obtained, the Vidas SET2 detection kit can be used to assess the safety of milk products for SEs.

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At the end of 2009, six food poisoning outbreaks caused by staphylococci were reported in France. Soft cheese made from unpasteurised milk was found to be the common source of the outbreaks. Staphylococcal enterotoxin type E was identified and quantified in the cheese using both official and confirmatory methods of the European Union Reference Laboratory (EU-RL). To our knowledge, this is the first report of food poisoning outbreaks caused by staphylococcal enterotoxin type E in France.