METHICILLINE RESISTANT STATUS OF COAGULASE NEGATIVE STAPHYLOCOCCUS ISOLATED FROM BOVINE MASTITIS

Abstract

Mastitis continues to be a major economic issue for dairy producers all over the world. A total of 100 milk samples from mastitic buffaloes and cows were subjected to bacteriological examination in the department of Veterinary Microbiology for the isolation of methicillin-resistant Staphylococcus aureus. 68 staphylococci spp. were isolated on the basis of colony morphology, haemolytic pattern on blood agar plates and growth on mannitol salt agar plates. Gram’s staining; catalase test, clumping factor test, coagulase test and mannitol fermentation tests were performed for the confirmation of Staphylococcus aureus and Staphylococcus epidermidis. 52 Staphylococcus aureus and 16 Staphylococcus epidermidis were purified on mannitol salt agar slants. Nitrocefin disks (Fluka) were used for the detection of beta-lactamase activity of these staphylococci. Out of 52 spp. of Staphylococcus aureus, 16 (30.76%) were found positive for beta-lactamase production; similarly, out of 16 spp. of Staphylococcus epidermidis 4 (25%) were found positive for beta-lactamase production. 29.41% of isolated staphylococci were found positive for beta-lactamase production through nitrocefin test. This beta-lactamase producer was subjected to antimicrobial susceptibility testing through disk diffusion test using oxacillin 1μg and cefoxitin 10μg antibiotic disks. Twenty two 22 (32.35%) isolates of staphylococci from a total of 68 were resistant to these disks hence declared as methicillin-resistant staphylococci. These methicillin-resistant staphylococci were subjected to antibiotic sensitivity testing through disc diffusion test using enrofloxacin, norfloxacin, chloramphenicol and amoxycillin discs. The results of in vitro sensitivity tests showed that enrofloxacin was most effective followed by norfloxacin and chloramphenicol. Amoxycillin was found ineffective. The aspect of methicillin-resistantce should be kept in mind for the treatment of staphylococcal mastitis.