Enterotoxigenic and Antimicrobic Susceptibility Profile of Isolates from Fresh Cheese in Croatia.

Certain strains harbour staphylococcal enterotoxin genes and hence can produce enterotoxin during their growth in food. Therefore, food can be a source of staphylococcal food poisoning, one of the most common food-borne diseases worldwide. Epidemiological data show that is often present in raw milk cheeses, and consequently, cheeses are often the source of staphylococcal food poisoning outbreaks. The aim of this study was to determine the phenotypic characteristics of isolates from fresh cheese, including antibiotic susceptibility; the presence of classical sea-see enterotoxin genes through molecular methods; and the isolate's ability to produce SEA-SEE enterotoxins in vitro through reversed passive latex agglutination. A total of 180 coagulase-positive staphylococci were isolated from 18 out of 30 cheese samples, and 175 were confirmed as through latex agglutination and API STAPH tests. All isolates possessed phenotypic characteristics typical for , with certain variations in the egg yolk reaction (18.3% of the isolates showed a weak reaction and 28% no reaction at all) and haemolysis pattern (36.6% of the isolates produced double-haemolysis and 4.6% were non-haemolytic). Antibiotic resistance was observed in 1.1% of the isolates and to mupirocin only. Real-time PCR detected the gene in 34 (19.4%) isolates, but most isolates (80.6%) were not enterotoxigenic. For all 34 (19.4%) strains that carried the gene, the RPLA method detected the production of the SEC enterotoxin in vitro. For those enterotoxigenic strains, the possibility of enterotoxin production in fresh cheese could not be ruled out.