engleski

Staphylococcus aureus and its enterotoxins in domestic cheese

Epidemiological and scientific data show that Staphylococcus aureus is often found in raw milk cheeses. Certain strains of S. aureus produce enterotoxins during their growth in favorable conditions in food, which are causative agents of staphylococcal food poisoning. Compliance with the food safety criteria for staphylococcal enterotoxins in cheese has to be investigated whenever levels of coagulase-positive staphylococci exceed 105 cfu/g. The aim of this study was to investigate the occurrence of S. aureus and staphylococcal enterotoxins in domestic cheeses produced in the Dubrovnik area, as well as the in vitro enterotoxin production ability of S. aureus isolates. Out of 30 analysed cheese samples, 18 samples (60 %) were highly contaminated (average 6.9x105 cfu/g) with S. aureus strains. In 17 cheese samples (56.7 %), the S. aureus number was above legal safety criteria. However, staphylococcal enterotoxins were not detected in any of the cheese samples. A total of 175 S. aureus isolates were collected from 18 cheese samples and confirmed by a latex agglutination test. Enterotoxin production in vitro was detected in 37 isolates (21.1 %) by the ELISA method (VIDAS SET2). In 34 out of 37 isolates, the reversed passive latex agglutination (RPLA) method detected the production of staphylococcal enterotoxin C. Enterotoxigenic strains originated from 8 cheese samples of two cheese manufacturers. Although highly contaminated, even with enterotoxigenic strains, staphylococcal enterotoxins were not detected, indicating that the intrinsic characteristics of cheese play an important role in enterotoxin production. However, isolated strains possess enterotoxigenic potential so enterotoxin production in cheeses cannot be ruled out.

ELISA ; RPLA ; staphylococcal enterotoxins

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