Abstract
Methicillin-resistant Staphylococcus aureus (MRSA), which is one of the most important nosocomial pathogens of humans, has recently emerged in animals. The predominant staphylococcal species in dogs is S. pseudintermedius. Methicillin-resistant S. pseudintermedius (MRSP) is now increasingly common in veterinary medicine. Since identification of S. pseudintermedius requires molecular methods, commercial clinical laboratories have not been able to identify it. This study reviewed etiologic agents in 10 dogs with pyoderma from which MRSA had been previously isolated in a clinical laboratory. Exudate swabbed from each dog was analyzed by two commercial laboratories (Lab A and B) and also by multiplex-PCR (M-PCR) for species identification of coagulase-positive staphylococci. The three results were compared. Among 10 isolated strains, 8 strains were identified as S. pseudintermedius, and 2 were identified as S. schleiferi by M-PCR. All strains except for one were tested positive for methicillin resistance. Results from both commercial clinical laboratories were poor. Lab A misidentified 9 strains as MRSA. Lab B reported none of the strains as methicillin-resistant and identified 7 strains at genus level (Staphylococcus sp.). It is essential to determine methicillin resistance in staphylococcal infections and the criteria differ with species, thus inadequate species identification could have an adverse effect on treatment decisions.
