摘要 : A study was conducted with the objective of isolation and molecular characterization of <i>E. coli</i> and <i>S. aureus</i> and identifying the efficacy of different antimicrobials against the bacteria associated with the mastitis... 展开 A study was conducted with the objective of isolation and molecular characterization of <i>E. coli</i> and <i>S. aureus</i> 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. <i>Escherichia coli</i> (18.18%), <i>Staphylococcus aureus</i> (42.14%), coagulase negative staphylococci (23.96%), <i>Streptococcus</i> spp. (3.30%), <i>Micrococcus</i> spp. (14.04%) and <i>Bacillus</i> spp. (5.78%) were isolated from 76 CMT positive milk samples and 45 samples from clinical cases of mastitis. <i>E. coli</i> 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. <i>E. coli</i> O157 and 088 were positive for <i>stx 1</i> genes by Polymerase Chain Reaction (PCR). Twenty six (78.7%) isolates of <i>S. aureus</i> 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. 收起