Identification of bacterial pathogens in dry bovine udder and their antimicrobial susceptibility

Abstract

Mastitis is a multi-etiological production disease of dairy cows worldwide. The likelihood of developing clinical mastitis in subsequent calving is enhanced by intramammary infections with pathogens during the late dry and post-calving period. There is an increase in the occurrence of intramammary infections during early and late dry period. Thirty apparently healthy, pregnant cross-bred dairy cows were screened for the presence of contagious mastitis pathogens in the secretions taken after 48 h of cessation of milking. A total of 118 bacterial isolates were obtained from the secretions collected from 108 quarters, and identified using morphological and cultural characteristics. Among them, 50.8 per cent were coagulase negative Staphylococci (CNS), 16 per cent were coagulase positive Staphylococci (CPS) and 27.1 per cent were Streptococci isolates. Micrococci and E. coli constituted 2.5 per cent each and Klebsiella spp. formed 0.8 per cent of the total isolates obtained. The CNS isolates identified included 22 S. chromogens, 14 S. xylosus, 12 S. saprophyticus, six S. hominis and S. epidermidis each. Among the CPS isolated 11.8 per cent were S. aureus and 4.2 per cent were non-aureus coagulase positive Staphylococcus which included three S. hyicus and two S. pseudointermedius. Molecular confirmation of S. aureus, CNS isolates, St. agalactiae were done by targeting nuc, cns and 16SrRNA gene respectively. Identification of bacterial pathogens that are present during dry period can help in formulating an effective dry cow therapy. Antibiogram studies of the isolates obtained were done using in vitro antibiotic sensitivity testing method.