Characterization and antimicrobial sensitivity of the pathogens isolated from bovine mastitis with special reference to Escherichia coli and Staphylococcus spp.

Abstract

A study was conducted with the objective of isolation and molecular characterization of E. coli and S. aureus and identifying the efficacy of different antimicrobials against the bacteria associated with the mastitis. All the milk samples collected aseptically, tested for mastitis by California Mastitis Test (CMT), revealed 8 (27.58%) and 68 (24.63%) samples positive for subclinical mastitis from yak and cattle, respectively. Escherichia coli (18.18%), Staphylococcus aureus (42.14%), coagulase negative staphylococci (23.96%), Streptococcus spp. (3.30%), Micrococcus spp. (14.04%) and Bacillus spp. (5.78%) were isolated from 76 CMT positive milk samples and 45 samples from clinical cases of mastitis. E. coli were serotyped as O13, O132, O88, O26, O162, O88, O86 and O157. Sorbitol was not fermented by serotype O157 and it was isolated and reported for the first time from animal origin in Sikkim, India. E. coli O157 and O88 were positive for stx 1 genes by Polymerase Chain Reaction (PCR). Twenty six (78.7%) isolates of S. aureus showed strong association of DNAse and coagulase and all were untypable with the international sets of phages. It was observed by disc diffusion test that nitrofurantoin and tetracycline (97.77% each) to be most effective antimicrobial followed by chloramphenicol (95.55%) and cephotaxime (91.11%) against the pathogens associated with bovine mastitis.