Contamination and Antimicrobial Susceptibility Testing of Staphylococcus aureus Isolated from Pork in Fresh Markets, Nongchok District, Thailand

We surveyed Staphylococcus aureus contamination in 110 pork samples from 12 fresh meat markets in Nongchok district, Bangkok, Thailand, and performed antimicrobial susceptibility testing with the disk diffusion method. The prevalence of S. aureus was 28.18%, and 52 strains were isolated. Antimicrobial susceptibility testing using the disk diffusion method revealed that 80.77% of the isolates were resistant to tetracycline and 76.92% to ampicillin. All strains were 100% susceptible to cloxacillin, cefoxitin, gentamicin, and cefazolin. The high percentage of antibiotic resistance to tetracycline and ampicillin was attributed to their use in treating infections in farmed animals and their addition to animal food for disease prevention. Interestingly, the present study revealed the intermediate resistance of S. aureus (13.46% of S. aureus-positive pork samples) to vancomycin which is a common medicine for treating severe infection in humans, suggesting that the trend of resistance might increase and becoming a serious problem of public health for both humans and animals.