Staphylococcus pseudintermedius colonization patterns and strain diversity in healthy dogs: a cross-sectional and longitudinal study.

This is the first large-scale study of Staphylococcus pseudintermedius colonization and diversity in healthy dogs where samples were collected over a long time and strains were identified by PCR according to the current taxonomy of the S. intermedius group and typed by a highly discriminatory method such as pulsed field gel electrophoresis (PFGE). A cross-sectional study of nasal, oral, perineal and inguinal carriage in 119 healthy dogs was followed by a longitudinal study where oral and perineal carriage was examined in 16 dogs for 10 times over a period of 1 year. Altogether we collected 762 samples and 285 S. pseudintermedius isolates, 182 of which were typed by PFGE to determine spatial and temporal strain diversity within individual carriers. In the cross-sectional study, S. pseudintermedius was isolated from at least one body site in 82 (69%) of the 119 dogs. The most frequent carriage sites were the perineum (66%) and the mouth (65%) followed by the nose (27%) and the groin (23%). PFGE analysis showed high heterogeneity among the isolates originating from different body sites of the same dog. Fifteen of the 16 dogs sampled longitudinally carried S. pseudintermedius in at least one sampling time, including six dogs that were negative in the cross-sectional study. Our results indicate that S. pseudintermedius carriage in dogs is more frequent and heterogeneous than S. aureus carriage in humans. This observation might reflect the hygienic standards and social behavior of the canine host, which facilitates transmission of this bacterium in the dog population.