Morphological characterisation and antimicrobial resistance of bacterial isolates from bovine mastitis

Abstract

The antimicrobial susceptibility of the pathogens is essential for the successful treatment of bovine mastitis. Antimicrobial resistance develops in microbes as a result of indiscriminate use of antibiotics. Therefore, regular screening is required for the selection of appropriate and effective antimicrobials. A study was carried out in 60 crossbred dairy cows in early lactation with the objective to assess the morphological characteristics and antimicrobial resistance of bacterial isolates from bovine mastitis. California mastitis test (CMT) was done for 235 individual quarter milk samples. Isolation of bacteria was done by direct streaking of the individual quarter CMT positive milk samples on to blood agar followed by incubation of the plates at 37 °C for 24 h. On Gram's staining, 32 isolates were found to be Gram positive cocci, three were Gram positive bacilli and ten were Gram negative bacilli. The disc diffusion assay revealed that antimicrobial resistance was highest against tetracycline (71.11 percent), followed by resistance to ampicillin and ceftriaxone-tazobactam (66.67 percent), ceftriaxone (64.44 percent), amoxicillin-sulbactam (62.22 percent), amikacin (57.78 percent), ceftriaxone-sulbactam (55.56 percent), enrofloxacin (46.67 percent), amoxicillin-clavulanate (40 percent), ciprofloxacin (37.78 percent) and gentamicin and co-trimoxazole (28.89 percent).