Incidence of Enterotoxin-Producing MRSA in Bovine Mastitis Cases, Bulk Milk Tanks and Processing Plants in Thailand

摘要

Methicillin Resistant S. aureus (MRSA) are virulent strains of S. aureus which have become resistant to most antibiotics. The emergence of MRSA is a serious public health concern worldwide. The present study sought to determine the distribution of enterotoxin-producing MRSA in Thailand using multiplex PCR. A total of 375 S. aureus isolates obtained from 598 mastitis cases, 376 bulk tank milk samples and 46 pasteurized milk samples were investigated for phenotypic methicillin resistance. Of these 375 isolates, 74 were found to be methicillin resistant. Variation in the SE encoding genes was detected. A total of 61 isolates harbored at least one classical SE gene, 30 isolates possessed only one type of enterotoxin gene and the remaining 31 were found to be positive for more than one toxin gene. The genes most frequently detected were seb and sed. Isolates obtained from mastitis cases had the highest incidence of enterotoxin genes followed by bulk milk isolates. On comparing the data relative to the different dairy locations, the isolates from Khon Kaen province harbored most detected enterotoxin genes. This was the only location where MRSA isolates from both mastitis milk and bulk milk were found harboring enterotoxin genes. Among the 5 S. aureus strains isolated from pasteurized milk only one isolate was MRSA. The strain which was isolated in Mahasarakham was positive for the sed gene. The current study has detected enterotoxigenic MRSA in mastitis milk, bulk milk and also pasteurized milk from Thailand. Further detailed analysis of functional genomics is now warranted to gain a better understanding of enterotoxin activity and virulence.