Pyoderma is one of the most important dermatological disorders encountered in small animal practice and S intermedius is the main etiological agent implicated. Although methicillin-resistant Staphylococcus aureus is being reported worldwide, MRSI has become an emerging problem only recently. The present study was undertaken with the objective of detecting the occurrence of methicillin-resistant staphylococci (MRS) in dogs with pyoderma.

Samples from 91 dogs (Veterinary College Hospital, Bangalore, India) suspected for pyoderma were subjected to culture, coagulase testing, biochemical characterization and methicillin antibiotic sensitivity testing by disc diffusion. All the 91 samples showed growth on mannitol salt agar and 88 isolates were coagulase positive (96.70%). Fourteen of the 88 isolates were found to be methicillin resistant phenotypically (15.91%). Six isolates were subjected to genotypic characterization by DNA extraction and PCR of which four yielded 304 bp amplicons corresponding to mecA gene specific to methicillin resistance. Methicillin resistance is said to be primarily due to a modified penicillin binding protein PBP2a encoded by the mecA gene which is located on one of the six types of staphylococcal chromosomal casettes (SCCs). Occurrence of MRSI is being reported for the first time from India. Only four of the six isolates were genotypically positive for methicillin resistance. This could be either because MRS are also said to contain additional genetic material besides mecA such as gene encoding for Panton-Valentine leucocidin or due to overestimation of methicillin resistance by disc diffusion.