Antibiotic resistance of Staphylococcus intermedius strains isolated from 53 natural cases of canine pyoderma

Samples for bacterial cultures on blood agar were obtained from the skin lesions of 53 dogs demonstrating the typical clinical and cytological features of superficial (n=17) or deep (n=36) pyoderma. None of them had received any kind of antimicrobial therapy within the previous month. The Staphylococcus looking colonies were recultured on blood and Chapman agar for staphylococcal species identification and biotyping. All 53 coagulasepositive staphylococcal isolates were eventually identified as S. intermedius. The susceptibility for each of these isolates was tested against 12 different antibiotics with the disc diffusion method. Resistance rates were found to be 0% for amoxicillin/clavulanate, 11.3% for oxacillin, 7.5% for cefalexin, 5.7% for enrofloxacin, 32.1% for erythromycin, 11.3% for tylosin, 20.8% for lincomycin, 18.9% for clindamycin, 32.1% for doxycycline, 5.7% for amicacin, 7.5% for chloramphenicol and 92.5% for trimethoprim/sulfamethoxazole. No correlation between the resistance pattern and either the age, breed, sex, and the animals' lifestyle, or the depth of skin infection, the presence or not of underlying diseases and any past treatment with antibiotics was identified.