Occurrency of Malassezia pachydermatis and other infectious agents as cause of external otitis in dogs from Rio Grande do Sul state, Brazil (1996/1997)

The purpose of this work was to evaluate the frequency of Malassezia pachydermatis infection and other infectious agents in dogs with external otitis and with healthy auditory tubes. Clinical manifestations of external otitis were evaluated. Samples from the auditory tube of 102 dogs with otitis and from 32 healthy dogs were submitted to direct microscopic examination and cultured in blood agar and Sabouraud dextrose agar with chloramphenicol and cycloheximide. Direct examination showed more than ten cells of M pachydermatis in 52.0% of the samples from dogs with otitis, but in only 21.8% of the healthy auditory tube samples. M. pachydermatis was isolated in 37.5% of the samples from dogs with healthy auditory tube and 76.5% (p<0.01) of the samples from dogs with otitis. There was an association between M pachydermatis and Staphylococcus aureus (p<0.01), but not with Pseudomonas aeruginosa (p>0.05). Infection by M pachydermatis was prevalent in the following breeds: Cocker Spainel, German Shepherd and Brazilian Fila. No differences were found in frequency of the infection in relation to age, sex and ear anatomy of the dogs. Otomycosis were predominantly ceruminous and erythematous. M. pachydermatis was the most frequent agent in external otitis.