Molecular studies on antimicrobial resistant genes in predominant staphylococci and E. coli isolates from bovine mastitis in different regions of Karnataka

Abstract

Bovine mastitis is a persistent and major problem in the dairy industry globally. Staphylococci and Escherichia coli are predominantly responsible for this condition. The aim of this study was to look for the genes associated with antimicrobial resistance in these predominant bacteria isolated from bovine mastitis in different regions in Karnataka. In all, 211 bacterial isolates were recovered from bovine mastitis cases in Karnataka. Of these, 85, 23 and 47 were Staphylococcus aureus, S. epidermidis and E. coli, respectively, as confirmed by PCR. Among S. aureus, blaZ was detected in 61.17% (52/85), mecA and tetK detected in 3.52% (3/85), aacA-aphD, ermC and strA genes detected in 4.7% (4/85), tetM was detected in 16.4% (14/85) and strB in 7.05% (6/85) isolates. None of the isolates contained tetO and ermA genes and 30.58% (26/85) isolates did not reveal any of the genes. Among S. epidermidis, blaZ was detected 43.47% (10/23), mecA and tetM detected in 30.43% (7/23), aacA-aphD and ermC detected in 13.04% (3/23), tetK detected in 8.69% (2/23), strA detected in 4.34% (1/23) and strB detected in 21.73% (5/23) isolates. None of them had tetO and ermA genes and 13.04% (3/23) isolates did not reveal any of the genes screened. Among E. coli, blaTEM and tetA genes were detected in 100% (47/47), blaSHV and strA were detected in 31.9% (15/47), blaOXA 30 detected in 12.76% (6/47), tetM and tetB detected in 2.12% (1/47), and strB was detected in 51.06% (24/47). None of the isolates contained aacA-aphD, mecA, tetO, tetK, ermA and ermC genes. This genetic profile of prevalence of antimicrobial genes for varied antibiotics/antimicrobials indicates the possible wider antimicrobial resistance among the predominant species of bacteria causing bovine mastitis. Further, phenotypic characterisation of these isolates with respect to their antimicrobial resistance would be of significance.