Application of nitrocefin test for the direct detection of methicillin resistant staphylococcus aureus from bovine mastitis milk samples

Mastitis continues to be a major economic issue for dairy producers in most parts of the world including pakistan. staphylococcus (s.) spp. are frequently isolated from bovine and bubaline mastitis. the indiscriminate use of antibiotics has led to the development of resistant strains of staphylococci and this factor contributed to the difficulties in its elimination from dairy herds leading to heavy economic losses to the industry. milk samples were collected from mastitic buffaloes and cows from livestock farms around faisalabad,pakistan and one hundred were selected on the basis of surf field mastitis test. isolation,identification and bacteriological examination were carried out through growth on blood agar,grams' staining,catalase,clumping factor,coagulase and mannitol fermentation test. the purification of staph isolates was done on mannitol salt agar. disc diffusion (oxacillin & cefoxitin) and nitrocefin tests were used to detect the production of β-lactamase by staphylococci and hence called methicillin-resisitant staphylococci (mrs). the mrs were subjected to antimicrobial susceptibility testing through disc diffusion method against antibiotics including enrofloxacin (5μg),norfloxacin (10μg),amoxycillin (25μg) and chloramphenicol (10μg). out of 100 mastitis smaples,68 were carrying staph spp. including s. aureus (76.47%) and s. epidermidis (23.53%). nitroceffin test detected 30.76% as mrs. aureus (mrsa) and 25% coagulase negative methicillin resistant s. epidermidis. the disc diffusion test detected 32.69% as mrsa and 37.5% as mrse. nitrocefin discs applied directly to 25 milk samples,could detect ~25%,while,disc diffusion test could identify 40% as mrs. antimicrobial sensitivity test revealed that enrofloxacin was most effective followed by norfloxacin and chloramphenicol. while,amoxycillin was found resistant. the use of nitrocefin test proved better than disc diffusion method for the detection of mrs. furthermore,aspect of methicillin-resistance must be considered while suggesting the treatment of mastitis due to staphylococcus spp to minimize the losses.