Nasal carriage of methicillin-resistant <i>Staphylococcus pseudintermedius</i> in dogs treated with cephalexin monohydrate.

Abstract

This study aimed to investigate the nasal carriage of methicillin-resistant <i>Staphylococcus pseudintermedius</i> (MRSP) in dogs treated with oral cephalexin monohydrate. Ten dogs with superficial pyoderma were monitored longitudinally for carriage of MRSP for up to 1 year after treatment; the strains were typed and antibiograms were determined. Methicillin-susceptible <i>S. pseudintermedius</i> (MSSP) was recovered prior to treatment in all dogs and could be isolated after 12 months in 1 dog. Methicillin-resistant <i>Staphylococcus pseudintermedius</i> was detected within 1 week of treatment in all dogs, and 3 clones represented by ST45, ST112, and ST181 were consistently present for up to 12 months after treatment. All MRSP isolates were resistant to at least 7 common antimicrobials. Oral cephalexin monohydrate treatment selected for strains of multi-resistant MRSP, which were still present after 1 year.