Detection of enterotoxigenic Staphylococcus aureus in raw and pasteurized milk

Abstract

The aim of this study was to investigate staphylococcal enterotoxins (SEs) by ELISA, and detect the five classical sea, seb, sec, sed, and see genes by real-time PCR in Staphylococcus aureus isolates from raw and pasteurized milk samples. Staphylococcus spp. were isolated from 98 out of 100 raw milk samples, and in 6 out of 100 pasteurized milk samples. On further biochemical tests, S. aureus was isolated in 48 samples (48%) of raw milk (n=100) and in one sample (1%) of pasteurized milk (n=100). Ten (10%) out of 100 raw milk samples were positive for at least one enterotoxin, and the most frequently observed SE was SEA (10%), followed by SEE (7%) and SEB (6%), but none of the isolates were positive for SEC and SED. At least one of the SEs gene types (sea, seb, sec, sed, see) was detected in 45 (93.8%; 45/48) S. aureus isolates from raw milk samples. sec, sea, seb, sed, and see genes were observed in 56.2%, 39.5%, 31.2%, 29.1% and 14.5% of strains respectively. The enterotoxin genes were the single type in 21 (46.7%) of the 45 isolates, there were two in 15 (33.3%), three in six (13.3%), four in two (4.4%), and one (2.2%) in all gene regions. The SE gene was not detected in the S. aureus (n=1) isolate from pasteurized milk. As a result of this study, the presence of enterotoxigenic S. aureus in raw milk was revealed, and it was pointed out that these SEs may contribute to cases of staphylococcal foodborne poisoning (SPF).