Detection of staphylococcal enterotoxin genes in raw milk samples by real-time PCR

Presence of significant level of enterotoxigenic S. aureus in raw milk of sheep, goat and donkey may cause serious food borne disease. Many people worldwide, use raw milk in their daily life but data on presence of virulence genes in cow, sheep, goat and especially donkey milk seems to be very limited. For this reason, aim of this study was to determine the presence both S. aureus and nine staphylococcal enterotoxin genes in cow, sheep, goat and donkey milks. A total of 231 raw milk samples were collected from 48 cow, 65 goat, 65 sheep and 53 donkey were collected. To detect presence of S. aureus both conventional culture and real-time PCR were used and to detect nine staphylococcal enterotoxin genes directly in milk, real-time PCR was performed. Conventional culture and real-time PCR results were found to be similar for presence of S. aureus and it was detected in 52 (22.51%) out of 231 raw milk samples. Staphylococcal enterotoxin genes were detected in 27 out of 52 S.aureus positive samples and a total of 62 enterotoxin genes were detected in these samples. However enterotoxin genes could not be detected in two S. aureus positive donkey milk. Hence, real-time PCR proved to be reliable and faster than conventional methods to detect presence of enterotoxigenic S. aureus in milk. Raw milk samples from different animals many contain enterotoxigenic S. aureus. Therefore, one should be careful during raw milk consumption as enterotoxigenic S. aureus in milk may cause dangerous public health problem which need routine screening for this pathogen in milk.