Aims: This study was undertaken to investigate whether the antibiotic resistance of Staphylococcus aureus and Staph. intermedius varies with the site of isolation, sex or age of dogs. Methods and Results: A total of 867 isolates of Staph. aureus and 1339 isolates of Staph. intermedius were obtained from nose, eye, ear, reproductive extremity, urine, abscess, skin and throat isolates. Staphylococcus intermedius isolates were isolated most frequently and adult and male dogs were more common compared with juveniles and ⁄ or female dogs. Antimicrobial resistance was commonly found for penicillin G, lincomycin, tetracycline and trimethoprimsulphamethoxazole in both Staphylococcus species. Surprisingly, we detected significant resistance to cloxacillin in male (67AE1%) and female (69AE4%) Staph. aureus isolates, irrespective of the anatomical site of isolation. The resistance or susceptibility of isolates of Staph. aureus from reproductive extremities and isolates of Staph. intermedius from ear, eye and abscess sites was associated with the age of the animal. Conclusions: Antimicrobial susceptibilities in Staph. aureus and Staph. intermedius often differed with regard to the site of isolation, sex and age of the animal. Significance and Impact of the Study: Increasing antimicrobial resistance in staphylococci in veterinary medicine complicates the empirical selection of antimicrobial agents. These complications reveal a continuously evolving, complicated multifactoral process of the site of isolation, sex and age of the animal.

Disc agar diffusion testing was performed on 547 isolates (two common pathogens) to determine if the site of isolation influenced the antimicrobial susceptibility results for a given bacterium. The most statistically significant results (P < 0.05) included cephalothin (ear) against Staphylococcus aureus and cephalothin (ear), lincomycin (ear), trimethoprim sulpha (ear), and amoxycilin and clavulanic acid (nose) against Staph. intermedius. Although the impact of these results (empirical treatment) is unknown, it is hypothesized that the site of isolation of Staph. aureus and Staph. intermedius may influence the choice of antimicrobial therapy in the dog and cat.