Isolation of bacteria causing mastitis from dairy cattle and its antimicrobial sensitivity in the South-Western region of Gujarat

Abstract

Mastitis is one of the major conditions that can reduce livestock production, population, quality of milk and farmers’ income. Many bacteria have been identified as etiological agents for mastitis. It has been frequently reported that many cases of mastitis are difficult to cure because of antimicrobial resistance. This study aimed to culturally identify various bacteria that cause mastitis in dairy cattle and their antimicrobial susceptibility testing. The study was conducted on 647 cattle milk samples received at the Veterinary Clinical Complex, Kamdhenu University, Junagadh with a history of clinical mastitis. Primary bacterial isolation was carried out by inoculating milk samples on the Brain Heart Infusion agar (BHI), morphological identification by Gram’s staining, and biochemical tests like-catalase, oxidase, and KOH test. 590 (91.19%) bacterial and 4 (0.6%) yeast isolates were found. 76 (11.74%) milk samples were found negative for bacterial isolation. The prevalence was calculated based on the percentage of samples positive for specific bacteria or yeast as an etiological agent. The prevalence was observed during the study as Staphylococcus spp., (45.71%); Gram-negative Bacilli, (26.27%); Bacillus spp., (3.43%); Streptococcus spp., (3.88%); Micrococcus spp., (1.34%); Corynebacterium spp., (2.84%); Pseudomonas spp., (4.62%) and Yeast, (0.6%). Antibiotics sensitivity test revealed levofloxacin as highly effective against Staphylococcus spp. (71.57%), Gram-negative bacilli (67.61%) as well as Bacilli spp. (86.95%), While gentamicin and levofloxacin were highly sensitive against Streptococcus spp. (84.62%). Higher susceptibility of Pseudomonas spp. (90.32%) was observed against cefpodoxime, While Corynebacterium spp. (73.68%) was sensitive to gentamicin. Micrococcus spp. revealed equal susceptibility (77.77%) against chloramphenicol and gentamicin. Cefoperazone was highly resistant to all isolated bacteria.