The occurrence of MRSA, MSSA and antibiotic resistance, related factors in area of dairy farming of Mahasarakham province, Thailand

Abstract

The occurrence of Staphylococcus aureus isolates, especially MRSA and MSSA isolates contaminated in raw milk, can cause endemic chronic bovine mastitis in the area of dairy farming, Maha Sarakham province of Thailand. A total of 165 milk samples were collected and S. aureus isolation was conducted by using a conventional method and PCR reaction of 994 bp of coagulase gene fragment. The results revealed 25 isolates of S. aureus that showed a positive result of coagulase gene. All 25 isolates were tested for MRSA and MSSA identification by mecA gene that demonstrated 2 mecA-positive MRSA isolates (n=2) and 23 mecA-negative MSSA isolates (n=23). Two isolates of MRSA indicated that the antibiotic resistance was a continuing problem in this area. All isolates have also been found to be isolates having enterotoxin producing genes including sea, seb, sec, and sed but not found any enterotoxin genes in MRSA and MSSA. To investigate factors related to MRSA, a survey research was conducted and showed that all farms used both of injecting drug and intramammary infusion antibiotics for their bovine mastitis treatment. The case-control study was divided into farms using oxytetracycline and penicillin as the first choice. The study found that oxytetracycline has been used routinely to treat mastitis in 2 and 18 farms having MRSA and MSSA, respectively. The odds of MRSA among farms using oxytetracycline was more than the odds of MSSA among farms using oxytetracycline. This study found that the often use of oxytetracycline in this area might create new properties of bacteria to become resistant to antibiotics. However, it may have other factors affecting bacterial resistances that need to study in further research to more understanding and to introduce the result of risk factors investigation to farmers.