The otic microbiota and mycobiota in a referral population of dogs in eastern USA with otitis externa

Background Canine otitis externa (OE) is a common inflammatory disease that is frequently complicated by secondary bacterial and/or yeast infections. The otic microbial population is more complex than appreciated by cytological methods and aerobic culture alone. Hypothesis/objectives Differences in bacterial and fungal populations of the external ear canal will correlate with specific cytological and culture‐based definitions of bacterial and Malassezia otitis. Animals Forty client‐owned dogs; 30 with OE and 10 with healthy ears. Methods and materials Prospective study comparing cytological samples, aerobic bacterial cultures and culture‐independent sequencing‐based analyses of the external ear canal. Subjects with OE included 10 dogs with only cocci [≥25/high power field (HPF)] on cytological evaluation and culture of Staphylococcus spp.; 10 dogs with rods (≥25/HPF) and exclusive culture of Pseudomonas aeruginosa; 10 dogs with only yeast on cytological results morphologically compatible with Malassezia spp. (≥5/HPF). Results Staphylococcus was the most abundant taxa across all groups. Ears cytologically positive for cocci had decreased diversity, and all types of OE were associated with decreased fungal diversity compared to controls. Conclusions and clinical importance Cytological and culture‐based assessment of the ear canal is not predictive of the diverse microbiota of the ear canal in cases of Pseudomonas or Malassezia otitis. Less abundant bacterial taxa in cases of staphylococcal OE are worth scrutiny for future biological therapy. RésuméContexteL'otite externe canine (OE) est une maladie inflammatoire fréquente souvent compliquée par une infection bactérienne et/ou fongique secondaire. La population microbienne auriculaire est plus complexe que l'examen cytologique ou la culture aérobie ne le montrent.Hypothèses/ObjectifsLes différences des populations bactériennes et fongiques du conduit auriculaire externe corrèlent avec les définitions spécifiques basées sur la cytologie et la culture de l'otite à Malassezia et bactérienne.SujetsQuarante chiens de propriétaires; 30 avec OE et 10 avec oreilles saines.Matériels et méthodesUne étude prospective comparant les échantillons cytologiques, les cultures bactériennes et les analyses basées sur le séquençage indépendant des cultures du conduit auriculaire externe. Les sujets avec OE incluaient 10 chiens avec des cocci uniquement [≥25/high power field (HPF)] sur cytologie et culture de Staphylococcus spp.;