Prevalence and infestation degree of yeast in canine otitis externa

Otitis externa is a persistent and recurrent problem, and the resistance of the involved pathogens to conventional drugs has made this a serious issue in veterinary medicine. This is an inflammation of the external ear canal in dogs that can be caused by bacteria or yeast. Often, these two causative agents are isolated together in combination. This study aimed to determine the prevalence of yeast and the degree of infestation of the isolated pathogens in canine otitis externa at veterinary clinics for small pets at the Department of Veterinary Medicine, University of Novi Sad, Serbia. Samples were taken from 60 dogs with clinical symptoms of otitis externa using a sterile swab and sent to laboratory for further mycological and bacteriological examination. In order to isolate the bacteria and yeast, conventional methods were used under aerobic conditions. Of the total samples, 53 (88.33%) were positive for at least one of the causative agents of otitis externa. Yeasts were isolated from 36 (52.94%) samples. The study showed that in comparing mixed and independent types of infection, in most cases 15/23 (65.22%) the degree of infestation with yeast was highest when the infectionwas mixed with bacteria. In relation to dog breeds, their ear forms and type of infection, more yeast samples (either as solo or mixed infection) were isolated from dogs with pendulous ears. It has been confirmed that Malassezia pachydermatis is the most common yeast pathogen of otitis externa in dogs, compared to other species of this genus, and it occurs in a higher degree of infestation in mixed infections than in solo infections. Dog breeds with pendulous ear form are more predisposed to yeast otitis externa than erect eared dog breeds.