In vitro antifungal activity of cold atmospheric microwave plasma and synergistic activity against Malassezia pachydermatis when combined with chlorhexidine gluconate

BACKGROUND: The antifungal efficacy of cold atmospheric microwave plasma (CAMP) against Malassezia pachydermatis has not been to be evaluated. OBJECTIVE: To examine the antifungal effects of CAMP against M. pachydermatis and its synergistic effects with chlorhexidine gluconate (CHX). METHODS: A M. pachydermatis isolate was collected from a dog with otitis externa and Malassezia dermatitis at the Seoul National University Veterinary Medical Teaching Hospital. The antifungal effect was determined by applying CAMP to a M. pachydermatis isolate that was incubated for 3 days at 37°C. After 1, 2, 3 and 5 min of application, the efficacy of the plasma treatment was determined according to the number of colony forming units (CFUs). A mixture consisting of inoculum and CHX was applied to evaluate the synergistic effect of the plasma treatment in the same way. RESULTS: The application of CAMP showed significant antifungal effects against M. pachydermatis. The antifungal effect of CAMP was enhanced by an increased exposure time and output power. The application of CAMP with 0.02% and 0.2% CHX resulted in lower survival rates against M. pachydermatis when compared with its sole application at 1 or 2 min. CONCLUSIONS: The study findings demonstrate that CAMP has a potential as a new antifungal option for M. pachydermatis and has synergistic antifungal effects with CHX in vitro. Clinical applications for CAMP are necessary to assess the antifungal efficacy for patients.