Participation and drug resistance of coagulase-positive staphylococci isolated from cases of pyoderma and otitis externa in dogs

Staphylococcus pseudintermedius is considered as a major pathogen in dogs, typically involved in skin and ear infections. Other staphylococci, as well as beta-hemolytic streptococci, Pseudomonas aeruginosa or yeast-like fungi of the genus Malassezia also play an important role in inflammation. Because of this diversity, an appropriate choice of antimicrobial agent(-s) can be difficult. A total of 474 tests were performed (including 255 pyoderma and 219 otitis externa cases). In the case of pyoderma, 82.4% of skin lesions were caused by stap hylococci. Co-infections with beta-hemolytic streptococci (17.3 %), Malassezia sp. (15.7 %) and P. aeruginosa (4.3 %) were also recorded. For external ear infections, the share of staphylococci in inflammation was lower (44.8 %) than that of Malassezia sp. (58 %). Relatively frequent co-infections with beta-hemolytic streptococci (18.8 %) and P. aeruginosa (7.8 %) were also noted. A total of 308 susceptibility tests for coagulase-positive staphylococci were performed (210 and 98 for skin and otitis externa, respectively). In >= 86 % of cases, amoxicillin potentiated with clavulanic acid, cephalexin and fluoroquinolones effectively inhibited the growth of all bacteria in vitro. A total of 25 isolates (24 S. pseudintermedius and one S. aureus) were considered as methicillin-resistant. The mecA gene was identified in 100 % of those strains but only 44 % of the isolates additionally carried the blaZ gene. All mecA-positive staphylococci were multidrugresistant, mainly to all beta-lactams, fluoroquinolones, linkozamides, macrolides as well as sulfonamides but always susceptible to mupirocin. Overall, multidrug-resistance varied between 6 % (otitis externa) and 9 % (inflamed skin) and may become a significant problem in the future.