Characterization of the otic bacterial microbiota in dogs with otitis externa compared to healthy individuals

Background Otitis externa is a common multifactorial disease in dogs. The diversity of the cutaneous microbiota in dogs appears to decrease in diseased states. However, little is known about the microbiota of the canine ear and how it is altered by disease. Hypothesis/Objectives To describe the otic bacterial microbiota in dogs with otitis externa compared to healthy dogs. Animals Samples were collected from 18 dogs with clinical and cytological evidence of otitis externa, and eight clinically normal dogs without cytological evidence of otitis externa. Methods and materials DNA from each sample was isolated and Illumina ® sequencing of the V4 hypervariable region of the 16S rRNA gene amplicons was performed. Sequences were processed using the bioinformatics software MOTHUR . Results Bacteria from 27 different phyla were identified. Affected ears had significantly decreased alpha diversity when compared to healthy ears. Community structure and membership also differed between the two groups. Linear discriminant analysis effect size analysis identified 153 operational taxonomic units ( OTU s) that were differentially abundant. Eleven OTU s were over‐represented in the affected ears, including Staphylococcus, Pseudomonas and Parvimonas . Conclusions The otic bacterial microbiota is much more complex than has been identified with previous culture‐based studies; otitis externa is accompanied by broad and complex differences in the microbiota.