Preventive use of a topical anti-inflammatory glucocorticoid in atopic dogs without clinical sign of otitis does not affect ear canal microbiota and mycobiota.

Abstract

Otitis externa is associated with a lack of bacterial/fungal diversity in atopic dermatitis. Clinical experience has shown that use of topical corticosteroids in the ear canal (EC) can prevent otitis. No data are available on the impact of this treatment on the EC microbiota. To observe the bacterial/fungal diversity in the EC and the clinical effect of topical corticosteroids administered over a four week period in atopic dogs without active otitis. Ten atopic dogs without active otitis. Mometasone was applied in the right EC, while the left was used as control. A clinical and cytological evaluation of the EC was performed. Swabs of each EC were analysed using next-generation sequencing methods. At the beginning of the trial, variations in microbiota and mycobiota were observed between dogs and also within individuals. Statistically, no significant difference was observed in alpha and beta diversity between the treated and the untreated group over time. Clinically, right and left EC diversities were no different at Day (D)28 (P=0.28). A significant difference was noted between D0 and D28 for the treated ears (P=0.012) and not for the untreated ears (P=0.63). No cytological evidence of microbes was found for treated ECs at D28. These data suggest that the use of topical corticosteroids as proactive treatment is unlikely to increase the risk of secondary microbial overgrowth. The positive clinical effect of this proactive treatment seems to be supported through cytological and otoscopic improvement.