CHARACTERIZATION OF STAPHYLOCOCCUS AUREUS ASSOCIATED WITH BOVINE MASTITIS

The present research was planned to study incidence, virulence properties and antibiogram of Staphylococcus aureus isolates recovered from bovine mastitis. A total 108 milk samples (48 cows and 60 buffaloes) from clinical and sub-clinical cases of bovine mastitis from different locations of Kolhapur and Sangali districts of Maharashtra state were collected during present investigation. Overall recovery of Staphylococcus spp. was 36 (33.33%) isolates (10 cows + 26 buffaloes) and 30 (27.77%) isolates were confirmed as S. aureus with an incidence rate of 16.66% in cows and 36.66% in buffaloes, whereas 6 (5.55%) isolates were other Staphylococcus spp. The incidence rate of S. aureus in subclinical and clinical mastitis was found to be 35.93% and 15.90% respectively. Conventional tube method for coagulase production, DNAse test and studies on haemolysis production of S. aureus isolates resulted in 9 (30%) CPS, 23 (76.66%) DNAse producing and 21 (70%) hemolytic strains. ABST of 30 S. aureus isolates by disc diffusion method indicated maximum resistance to Vancomycin (90%) followed by Ceftriaxone (80%), Penicillin-G (73.34%), Oxacillin (70%) and Amoxicillin (60%) whereas, the least resistance was observed to Methicillin (6.67%) and Chloramphenicol (10%). Multiple drug resistance was observed in 26 (86.66%) isolates. The PCR amplification of Coagulase gene (coa) of S. aureus isolates yielded 14 (46.66%) coagulase positive isolates with amplification sizes ranging from 600 to 850 bp. Four different coa genotypes were generated based on the sizes of amplicons viz. A, B, C and D. Out of 14 coa exhibiting strains of S. aureus, Genotype A (850 bp) was observed in 7.14% isolates, whereas genotype B (750 bp) in 14.28% isolates, 50% isolates were of genotype C (700 bp) and 28.57% of genotype D (600 bp). Amongst 14 coa positive isolates, 11 were from subclinical mastitis origin and only 3 were from clinical mastitis cases. All coagulase producing strains of S. aureus were haemolytic and DNAse producing with an exception of one DNAse negative strain.