Phenotypic antimicrobial profiling of Streptococcus spp. isolated from subclinical and clinical bovine mastitis

Mastitis occurs worldwide among dairy animals, and it has been described to have an extreme economic impact, despite the adopted control strategies. Due to indiscriminate use and acquisition of genetic components; bacteria are getting resistant to commonly employed antibiotics. This study aimed to investigate Streptococcus spp. found in mastitic milk Draminski samples of cows and buffaloes as well as the sensitivity of isolates to different antibiotics. A total of 190 milk samples were collected from various areas near Banaskantha, Gujarat, and analyzed for the presence of subclinical mastitis with an electronic conductivity meter, 4Q MAST, and CMT, and out of them 18 were found positive. Additionally, 95 milk samples from clinical mastitis were also collected. Therefore, a total of 113 milk samples were subjected to isolation and identification of Streptococcus spp. using microscopy, culture, and biochemical test-based species differentiation. As a result, a total of 17/285 (5.96%) isolates of streptococci were obtained, whose percent among mastitis-affected animals (17/113) was 15.04%. Among them respectively, 4 (23.52%), 6 (35.29%), and 7 (41.17%) belonged to species Strep agalactiae, Streptococcus dysgalactiae, and Streptococcus uberis. In disk diffusion-based antibiotic susceptibility testing, chloramphenicol, ampicillin/sulbactam, amoxicillin/clavulanic acid, and ampicillin were found to be 100% sensitive, whereas oxytetracycline, ceftriaxone, and cefoperazone showed resistance against the test isolates.