PHENOTYPIC CHARACTERIZATION OF METHICILLIN-RESISTANT STAPHYLOCOCCAL STRAINS ISOLATED FROM DAIRY CATTLE IN A RURAL COMMUNITY

Abstract

The emergence of methicillin-resistant staphylococci among livestock production have revealed different epidemiological dimension to the understanding of the staphylococcal infection. The aim of this study was to investigate methicillin-resistant staphylococcal strains isolated from raw milk and nasal cavity from free range dairy cattle in rural community using phenotypic profiling. A total of 283 samples were examined from free range dairy cattle (137 milk samples and 146 nasal swabs) were assessed between February and April 2015. Staphylococcal were isolated and positively identified using morphological and biochemical reactions. Of the 283 samples, 100 isolates (50 nasal and 50 milk samples) were methicillin-resistant Staphylococcus species and were further characterized by phenotypic methods. The antimicrobial resistance profiles of the isolates were determined using the phenotypic disc diffusion method. Phenotypic characterization using Modified Hodge Test showed that 45/50 (90%) and 48/50 (96%) of the isolates from nasal and raw milk revealed carbapernemase activity respectively. Also, 2/50 (4%) of the isolates from the nasal cavity and 4/50 (8%) of the isolates from raw milk were positive to Double Disc Synergistic Test and thus revealing metallo-?-lactamases (MBLs) production. Extended spectrum beta-lactamase activity, carbapenemase activity and metallo-beta-lactamase activity producing isolates are becoming prevalent in food animal settings. The detection of staphylococcal strains that are phenotypically resistant to oxacillin and methicillin are known to pose serious health concerns and are of great clinical relevance.