Methicillin-resistant Staphylococcus pseudintermedius Clonal Groups Isolated from Canine Pyoderma in Brazil

Background : Since the early reports of mecA -positive Staphylococcus ( S .) pseudintermedius isolates in the United States and in Europe were published, the frequency of methicillin-resistant S. pseudintermedius (MRSP) has increased among skin disease cases in dogs in many countries. Moreover, MRSP isolates frequently present a multi-drug resistant profile, which include most drugs used for the skin disease treatment. The distribution of multi- drug resistant MRSP clonal groups in turn varies according to geographic region. Despite the large dog population in Brazil, no data on the MRSP resistance profile or clonal groups have been reported. The aim of this study was to assess the antimicrobial resistance phenotypes and clonal relationships of MRSP isolates originating from dogs affected by recurrent skin diseases. Material, Methods & Results : Twenty-one epidemiologically unrelated isolates originating from dogs inflicted with a recurrent skin disease, which were treated at the Veterinary Hospital (HCV) of the Federal University of Rio Grande do Sul (UFRGS) in Porto Alegre, were included in this study. The isolates suspected of being MRSP were subjected to PCR analysis to confirm their identity. Identifications were made using PCR analysis that targeted the mecA gene and PCRRFLP that targeted the pta gene. Isolates were further assessed by a disc diffusion test for resistance to 13 antimicrobials. Clonal groups were determined according to spa typing and SmaI fingerprinting (Pulsed-field Gel Electrophoresis-PFGE) profiles. All 21 isolates were confirmed to be MRSP and displayed a multiple resistance profile. In total, 4 different spa types were identified, and the most prevalent was a novel spa type (tyA) described in this study. SmaI-macrorestriction analysis demonstrated that the MRSP isolates presented between seven and twelve fragments and were distributed among 15 PFGE profiles. One major clonal group belonging to the new spa type (tyA) and to a common PFGE cluster was identified. This clonal group displayed resistance to fluoroquinolones, macrolides, lincosamide, aminoglycosides, sulfonamides, tetracycline and rifampicin. Discussion : A major multi-drug resistant clonal group of S. pseudintermedius was identified, which was shown to cause recurrent canine pyoderma and which might be widespread among dogs in the region. Among the 13 new spa type tyA isolates, 11 were also grouped in a common PFGE cluster (A), indicating that recurrent skin disease in dogs treated at the HCV/UFRGS was often associated with one major MRSP clonal group (A/tyA). Additionally, this clonal group displayed resistance to most of the therapeutically important antimicrobial agents tested as fluoroquinolones, macrolides, lincosamide, aminoglycosides, sulfonamides, tetracycline and rifampicin. The clonal group was also resistant to ciprofloxacin, a fluoroquinolone not intended for animal treatment but highly valuable in human medicine. All drugs considered as a first-line choice, as well as most of the second-line drugs typically used for the treatment of skin diseases showed to be ineffective against the MRSP A/tyA group. Among the second-line drugs tested, only gentamicin showed a susceptibility profile among the isolates and might represent a therapeutic option. These data highlight the importance of culture and antimicrobial susceptibility testing as part of the routine diagnosis of skin diseases, as well as the need for hygiene and disinfection measures at small animal clinics to avoid the dissemination of multi-drug resistant MRSP clonal groups.