The isolation pattern of samples collected from dogs with both media (OM) and extern otitis (OE) was compared. Sixty-four dogs suffering from those conditions were studied over a 10-month period. Samples from the external ear were collected with sterile swabs while those from the middle ear were collected by osteotomy of the tympanic bulla. The microorganisms were cultured and identified according to methods previously described and to the susceptibility of antimicrobials according to the National Committee for Clinical Laboratory Standards agar diffusion test. Anaerobic bacteria were not isolated in any sample. All samples from OE showed bacterial and/or fungal growth. Concerning media otitis, this percentage was 48%. The most common microorganisms isolated from OE were Bacillus sp. (26.9%), M. pachydermatis (22.2%) and S. intermedius (21.7%) and those from OM were S. intermedius (32.5%), S. aureus subsp. aureus (22.5%) and non-fermentative Gram-negative rods (10.0%). Some difference was observed in the isolation pattern between media and extern otitis in 96.7% of the animals. High resistance rates of S. intermedius strains to penicillin G, ampicillin, erythromycin, tetracycline and clindamycin were found.
dog; otitis; antibiogram
