A laboratory survey of viral diseases occurred in horses in Argentina from 2007 to 2012

staphylococcal species is unclear. Non-aureus staphylococcal species, including Staphylococcus pseudintermedius and Staphylococcus delphini, are important pathogens in some species, can be multidrug resistant and could be a concern in horses. Methicillin-resistant or unusual staphylococci isolated at the Ontario Veterinary College routinely undergo further characterization. During 2011, six staphylococci isolates from horses that were not methicillin-resistant S. aureus (MRSA) were tested. Isolates were identified through MALDI-TOF, staphylococcal species-specific PCR and/or sodA sequence analysis. Isolates were further characterized, as indicated, by dru typing, PFGE, mecA PCR, penicillin-binding protein 2a (PBP2a) latex agglutination test (LAT), and broth microdilution or disc diffusion. Six isolates were evaluated. Two were identified as methicillin-resistant S. pseudintermedius (MRSP). These isolates, from the frontal sinus (1-yr filly with sinusitis) and urine (16-yr mare with urolith) were dt11a, a predominant MRSP clone in dogs. In addition to beta-lactams, both isolates were resistant to chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, levofloxacin, moxifloxacin, tetracycline and trimethoprim/sulfamethoxazole. Four isolates were initially identified biochemically as S. pseudintermedius, but ultimately determined to be S. delphini by sodA sequence analysis and S. delphini PCR. Three were classified as S. delphini group B and one Group A. The group B isolates were from a 7-yr mare (chronic otitis externa) and 4-yr and 5-yr mares (incidental findings from Streptococcus equi nasopharyngeal wash surveillance cultures). The Group A isolate was from a 5-yr mare (S. equi surveillance culture). All were methicillin-susceptible. One Group B isolate was resistant to erythromycin; the remaining isolates were susceptible to all tested antimicrobials. Two of the Group B isolates were closely related by PFGE (3 band difference) while the other two were unrelated to each other and the two related isolates. MRSP is an important emerging pathogen in dogs and cats, yet has been rarely identified in horses, with few cases reported worldwide. In one patient, Streptococcus zooepidemicus and Actinobacillus spp were also isolated so the clinical relevance of MRSP is unclear. However, the authors are aware of anecdotal reports of MRSP infection in horses in the province, so MRSP may be a mis-identified (mistaken for MRSA or MR-coagulase negative staphylococci) or emerging equine pathogen. Given the rapid expansion of this pathogen in dogs and its highly resistant nature, ongoing surveillance is needed. S. delphini has rarely (if ever) been identified in horses, but it may be misidentified with conventional methods. Although in these cases colonization/contamination appeared most likely, these findings suggest this opportunist can be found in horses and might be pathogenic in certain situations. Ongoing surveillance for the emergence of S. delphini and S. pseudintermedius in horses is indicated to determine whether they are of clinical relevance. A laboratory survey of viral diseases occurred in horses in Argentina from 2007 to 2012