Evaluation of otoscope cone disinfection techniques on contamination by Malassezia pachydermatis

Summary Background Otoscope cones (OCs) are used in veterinary medical practices to examine healthy or infected ears in dogs and cats. Since OCs are reusable equipment, they can be vectors of cross contamination/infection between patients. Objectives The objective was to evaluate the efficacy of different disinfection procedures applied on OCs contaminated by Malassezia pachydermatis. Material and methods OCs were soaked for 10 min in a suspension of yeasts 2.5 McFarland and then allowed to air dry. OCs were soaked for 10 min either in ethanol, chlorhexidine, hydrogen peroxide, peracetic acid disinfectant, enilconazole or water (positive control). They were then paper wiped or left to air dry. Each OC was sampled with two swabs that were inoculated on modified Dixon's agar and incubated at 32 °C. On day 3, the number of Colony Forming Unit (CFU) was counted. Results Ninety-six cultures were performed and the growth of Malassezia could be seen in all cultures from positive controls/water (over 200 CFU in 6 from 12 tests). Similar results were observed when enilconazole was used at 0.2% concentration (over 200 CFU in 3 from 12 tests). In rest, all the cultures were negative. Conclusions Enilconazole should be used at minimal concentration of 0.4%.