Study to assess in vitro antimicrobial activity of nine ear cleaners against 50 Malassezia pachydermatis isolates.

Abstract

BACKGROUND: Ear cleaning is an important part of the successful therapy of otitis externa. HYPOTHESIS/OBJECTIVES: To evaluate the in vitro activity of nine commercially available ear cleaners (Cerumaural(&#xae;), CleanAural Dog(&#xae;), Epi-Otic(&#xae;), MalAcetic Aural(&#xae;), Otoclean(&#xae;), Otodine(&#xae;), Sancerum(&#xae;), Surosolve(&#xae;) and TrizUltra&#x2122; + Keto) against 50 Malassezia pachydermatis isolates from clinical cases of canine otitis externa. To the authors' knowledge, this is the first study to analyse the in vitro susceptibility of a large number of M. pachydermatis isolates to a variety of ear cleaner products. ANIMALS: Forty-nine hospital population dogs diagnosed with otitis externa with Malassezia spp. present on cytological examination of ear swabs and culture. METHODS: The antimicrobial activity of nine ear cleaners was tested against 50 M. pachydermatis isolates from 49 clinical cases of canine otitis externa using an in vitro agar diffusion test. RESULTS: There were statistically significant differences in activity between ear cleaners, with five showing excellent in vitro anti-Malassezia activity (CleanAural Dog(&#xae;), Epi-Otic(&#xae;), MalAcetic Aural(&#xae;), Sancerum(&#xae;) and TrizUltra&#x2122; + Keto), two moderate activity (Otodine(&#xae;) and Surosolve(&#xae;)), one variable activity (Otoclean(&#xae;)) and one no activity (Cerumaural(&#xae;)). There was a significant overall difference in susceptibility between M. pachydermatis isolates tested (P < 0.001). CONCLUSIONS AND CLINICAL IMPORTANCE: Ear cleaners with activity against Malassezia may help to reduce the unnecessary use of antibiotic-containing polypharmaceutical ear medications. This study shows that the use of a large number of isolates may provide a more accurate account of the in vitro activity of a product.