ANTIBIOTIC RESISTANCE AND MOLECULAR DETECTION OF nuc AND mecA GENES OF STAPHYLOCOCCUS AUREUS ISOLATED FROM MASTITIC MILK

The emergence of methicillin resistant Staphylococcus aureus (MRSA) is mainly due to the presence of resistant genes. The objective of this study is to perform antibiotic susceptibility profiling and molecular detection of nuc and mecA genes of Staphylococcus aureus isolated from mastitic milk. A total of 105 milk samples were collected from dairy farms in the Faisalabad region. They were cultured on Staph-110 media and mannitol salt agar. Biochemical tests included catalase and coagulase, were also performed for the identification of Staphylococcus aureus. Antibiotic susceptibility profiling of MRSA was done by disc diffusion method and molecular screening of Staphylococcus aureus for the detection of nuc and mecA genes was done by using PCR. Selected 8 antibiotics based on previous history being commonly used in dairy practices. The prevalence of Staphylococcus aureus observed by PCR was 58.09%. Oxacillin (1µg) and vancomycin (30µg) showed 100% resistance, while enrofloxacin (5µg), amoxicillin (25µg), ampicillin (10µg), oxytetracycline (1µg), gentamycin (10µg) and tylosin (30µg) showed 1.64, 55.74, 73.77, 13.11, 1.64 and 11.74% resistance, respectively. Susceptibility percentages of enrofloxacin (5µg), amoxicillin (25µg), ampicillin (10µg), oxytetracycline (1µg), gentamycin (10µg) and tylosin (30µg) were 27.87, 37.70, 14.75, 19.67, 98.36 and 9.84%, respectively. Enrofloxacin (5µg), amoxicillin (25µg), ampicillin (10µg), oxytetracycline (1µg) and tylosin (30µg) showed 70.49, 6.56, 11.47, 67.21 and 78.69% intermediate resistance against MRSA. Among the mastitic cases, 58.09% were positive for Staphylococcus aureus. These isolates were susceptible to gentamycin in 98.36% and tylosin in 78.69% cases, so these antibiotics can be used for the treatment of mastitis.