PREVALENCE OF STAPHYLOCOCCUS AUREUS STRAINS IN RAW SHEEP MILK CHEESE AND ENTEROTOXIGENIC PROFILE

Abstract

The aim of the present study was to investigate the prevalence of S. aureus in raw sheep milk cheese and to assess the enterotoxigenic profile of the isolated strains. N.16 raw milk sheep cheese, collected from 8 artisan dairies, were analyzed to detect the presence of Coagulase Positive Staphylococci (CPS). In the frame of Regulation (EC) No 2073/2005 cheese samples were tested for the presence of staphylococcal enterotoxins (SEs) when a CPS count >105 cfu/g was detected. CPS isolates identified as S. aureus were analyzed using multiplex PCR for the detection of classical (sea-see) and enterotoxins-like (seh, sek, sel, sem, seo, sep) genes. S. aureus was recovered in all cheese samples and in 50% with levels >105 cfu/g. 14 strains carried at least one of the genes coding for enterotoxins. In none of the cheese samples SEs were detected. Although a correct acidification (pH 5.1-5.4 at 6 hours) was observed in dairies using natural starter culture, in cheese samples obtained from these dairies, CPS counts were greater (P<0.05) as compared with those where starter culture were not used. This result might be related to the main role of microbial competition on the control of S. aureus in early stage of cheesemaking. Further research is needed to better understand the effect of lactic acid bacteria competition on the growth of S. aureus.

Keywords

• S. aureus, raw milk sheep cheese, RPLA, enteroxins