Direct repeat unit (dru) typing of methicillin-resistant Staphylococcus pseudintermedius from dogs at a diagnostic laboratory in Atlantic Canada.

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) has emerged as major pathogen in dogs, being primarily isolated from skin, ears, surgical site infections, and wounds. The Atlantic Veterinary College (AVC) Diagnostic Bacteriology Laboratory is a principle reference laboratory for Atlantic Canada, and has seen a significant increase in the recovery of MRSP from samples submitted for routine culture and sensitivity. Currently, there are no reports investigating MRSP in dogs in this region. Sequence analysis of the mec-associated direct repeat units (dru typing) is a preferred method for strain typing MRSP. A significant difference in the distribution of predominant dru clusters has been reported between Europe, 5 U.S. states, and Ontario, Canada, with suggestion that dru types may be unevenly distributed in a single country. The objective of this study was to strain type the MRSP cultured at the AVC Diagnostic Bacteriology Laboratory using dru typing. Staphylococcal isolates recovered from dogs between January 2010 and December 2012 were tested. Staphylococci were identified using biochemical testing and methicillinresistance was confirmed by the presence of penicillin-binding protein 2a (PBP2'). A multiplex PCR assay was used to identify coagulase-positive staphylococci to the species-level. Isolates were typed by analyzing sequence data from the direct repeat units. To date, 115 MRSP isolates have been typed. 17 different dru types have been identified with the majority belonging to type dt11a (n=33, 28.7%), dt10h (n=27, 23.5%), dt9a (n=27, 23.5%), and dt11af (n=12,10.4%). The remaining 16 (13.9%) isolates were distributed between 13 different dru types, nine of which have not been previously identified: dt5k, dt6t, dt8ag, dt9ba, dt9bd, dt10bz, dt10cc, dt10cj, and dt11ca. Each of the previously unidentified dru types was represented by one isolate. The predominant dru types identified in this study are similar to those found in Ontario, Canada; however, a cluster analysis is needed to make further conclusions. Further work will include epidemiologic analysis of dru types and patient information. Results from this study will provide information on the MRSP situation in Atlantic Canada, furthering the understanding of the dissemination of this pathogen.