Genotypic identification of methicillin resistance and virulence factors in Staphylococcus spp. from bovine mastitis milk

The aim of this study was the genotypic characterization of methicillin resistance and virulence of Staphylococcus spp. from bovine mastitis cases. The study was designed to collect milk samples from 120 animals (90 lactating cows and 30 buffaloes) and screened using California mastitis test and somatic cell counts. Staphylococci were isolated on Baird-Parker, mannitol salt and identified based on their physiologically and species-specific biochemical tests. Antibiotic resistivity assay was performed using standard antibiotic disc diffusion technique for screening. On the basis of antibiograms, 26 strains were selected. Selective isolates were identified based on 16S rDNA gene sequencing. Virulence genes associated with Staphylococcus sp. viz. coa, ccr, sar, spa, clfA, ica complex, fnbA, and mecA were amplified on screened isolates. A total of 26 isolates, S. aureus, S. pasteuri, S. hominis, Micrococcus sp., and Macrococcus sp. were selected on the basis of all in vitro assay and their 16S rDNA sequences were submitted to NCBI, GenBank under the accession number KX821621 to KX821646. Out of 26 studied typed isolates, 19, 15, 14, 21, 6, 25, and 22 isolates give amplification for mecA, coa, spa, clfA, ccr, ica, fnbA, and sar genes, respectively. Four S. aureus possessed all virulence genes. Presence of methicillin resistance Staphylococci having virulence genes revealed that mastitis is a major concern nowadays affecting animal health, milk quality, and yield. Further genomic study of these isolates will provide broad new insights on virulence.