Changes in the ear canal microbiota of dogs with otitis externa.

AIMS: Otitis externa (OE), one of the most common ear diseases in dogs, is caused by bacterial pathogens such as Staphylococcus sp. To understand the network of microbial communities in the canine ear canal affected with OE, we performed a cross-sectional study using next-generation sequencing. METHODS AND RESULTS: Ear swab samples were collected from 23 OE-affected and 10 healthy control dogs, and the 16S rRNA gene sequenced using Illumina MiSeq. The otic microbiota in the OE-affected dogs showed significantly decreased alpha diversity compared to controls. The community composition also differed in the affected group, with significantly higher relative abundance of the phylum Firmicutes and the genus Staphylococcus (P = 0·01 and 0·04 respectively). Contrary to our expectations, the severity of the disease did not impact the otic microbiota in OE-affected dogs. CONCLUSIONS: The ear canal microbiota of OE-affected dogs is distinct from that of healthy dogs, irrespective of disease status. SIGNIFICANCE AND IMPACT OF THE STUDY: This study, one of the few detailed analyses of the otic microbiota, can provide practical information for the appropriate treatment of canine OE.