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

Background -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.Hypothesis/objectives -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. Animals -Ten atopic dogs without active otitis.Methods and materials -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.Results -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.Conclusions and clinical relevance -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.

Long‐term non‐surgical management of canine aural tympanokeratoma with repeated removal of middle ear keratinous debris and CT follow‐up

“…The dog had a history of sporadic bilateral otitis externa, and proactive maintenance treatment with topical corticosteroid has been demonstrated to reduce the risk of recurrence of otitis externa without causing negative effects on the aural microbiota. 39,40 In conclusion, this case of canine tympanokeratoma was managed for almost 2 years with repeated non-surgical middle ear evacuation procedures. Non-surgical management did not prevent recurrence, but it controlled the clinical signs and possibly limited the progression of destructive bony changes.…”

“…The right ear, with an intact tympanic membrane, was treated with a commercially available topical product containing betamethasone. The dog had a history of sporadic bilateral otitis externa, and proactive maintenance treatment with topical corticosteroid has been demonstrated to reduce the risk of recurrence of otitis externa without causing negative effects on the aural microbiota 39,40 …”

The Middle Ear Microbiota in Healthy Dogs Is Similar to That of the External Ear Canal

“…observed in the EEC in the present study was not noted in the previous studies in healthy owned dogs, using the same technique in the same laboratory [ 7 ]. Such divergence might be explained by environmental conditions (housed in kennel versus home) but also by individual and genetic factors (breed), as mentioned in other studies [ 13 , 34 , 35 ].…”

“…Many studies using 16S rRNA gene amplicon analysis profiling have described the microbiota of the EEC in normal and atopic dogs, with or without OE [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. These studies confirmed that normal EEC microbiota is much more complex than supposed with the bacterial cultures [ 7 , 8 ].…”

External Ear Canal Evaluation in Dogs with Chronic Suppurative Otitis Externa: Comparison of Direct Cytology, Bacterial Culture and 16S Amplicon Profiling

“…The DNA extraction, amplification and sequencing were performed as previously described [ 18 , 19 ].…”