Aim: In this study, the determination of isolation of microorganisms and antibiotic susceptibility of isolated bacteria in ear swab samples collected from dogs with otitis externa were aimed.

Materials and Methods: In this study, 58 ear swab samples were collected from 41 dogs with otitis externa. The microorganisms were isolated from the samples and identified by conventional bacteriological methods. The antibiotic susceptibilities of the isolates were determined by agar disc diffusion method.

Results: While 64 microorganisms were isolated from 52 (88.66%) of the samples, pathogen microorganism could not be isolated from 6 (10.34%) samples. S. aureus (31.25%) was the most frequently isolated agent. Also, coagulase negative staphylococci (CNS) (14.06%), Streptococcus sp. (12.5%), Corynebacterium sp. (6.25%), Proteus sp. (4.68%), Pseudomonas aeruginosa (3.13%) and Candida sp. (28.13%) were isolated, respectively. All of the S. aureus, Streptococcus sp., Corynebacterium sp. and CNS isolates and 66.67% of Proteus sp. were susceptible to amoxicillin-clavulanic acid. This bacterial isolates were found susceptible 65.22%, 52.17%, 47.83%, 43.48%, and 30.43% to enrofloxacin, amoxicillin and oxytetracycline, gentamicin, trimethoprim- sulfamethoxazole and erythromycin, respectively. All P. aeruginosa isolates to enrofloxacin and gentamicin, and 50% of this isolates were susceptible to oxytetracycline.

Conclusions: The differences in antibiotic susceptibility of the bacterial isolates shows that antibiotic susceptibility tests is necessary for treatment of dogs with otitis externa and yeasts should not be overlooked, due to high rates of Candida sp. isolation.