Antimicrobial susceptibility profiles of Staphylococcus intermedius isolates from clinical cases of canine pyoderma in South Africa

Successful treatment of canine pyoderma has become compromised owing to the development of antimicrobial resistance with accompanying recurrence of infection. Canine skin samples submitted to a veterinary diagnostic laboratory for microbiological culture and sensitivity between January 2007 and June 2010, from which Staphylococcus intermedius was isolated, were selected for this investigation. Antimicrobial resistance of S. intermedius was most prevalent with reference to ampicillin followed by resistance to tetracycline and then potentiated sulphonamides. In general, antimicrobial resistance was low and very few methicillin-resistant isolates were detected. Temporal trends were not noted, except for ampicillin, with isolates becoming more susceptible, and potentiated sulphonamides (co-trimoxazole), with isolates becoming more resistant. In general, both the Kirby-Bauer disc diffusion and broth dilution minimum inhibitory concentration tests yielded similar results for the antimicrobial agents tested. The main difference was evident in the over-estimation of resistance by the Kirby-Bauer test for ampicillin, co-trimoxazole, penicillin and doxycycline. Knowledge of trends in bacterial resistance is important for veterinarians when presented with canine pyoderma. Analysis of antimicrobial susceptibility profiles of S. intermedius isolated from canine pyodermas will guide veterinarians' use of the most appropriate agent and encourage prudent use of antimicrobials in companion animals.