In Vitro Biofilm Formation by Malassezia pachydermatis Isolates and Its Susceptibility to Azole Antifungals

Abstract

The yeast Malassezia pachydermatis, an opportunistic pathogen that inhabits the skin of various domestic and wild animals, is capable of producing a biofilm that plays an important role in antifungal resistance. The aim of this research study was to find the intensity of biofilm production by M. pachydermatis strains isolated from the ear canal of healthy dogs, and to determine the susceptibility of planktonic, adhered and biofilm-forming cells to three azole antifungals—itraco-nazole, voriconazole and posaconazole— that are most commonly used to treat Malassezia infections. Out of 52 isolates, 43 M. pachydermatis strains (82.7%) were biofilm producers with varying levels of intensity. For planktonic cells, the minimum inhibitory concentration (MIC) range was 0.125–2 µg/mL for itraconazole, 0.03–1 µg/mL for voriconazole and 0.03–0.25 µg/mL for posaconazole. Only two isolates (4.7%) were resistant to itraconazole, one strain (2.3%) to voriconazole and none to posaconazole. For adhered cells and the mature biofilm, the following MIC ranges were found: 0.25–16 µg/mL and 4–16 µg/mL for itraconazole, 0.125–8 µg/mL and 0.25–26 µg/mL for voriconazole, and 0.03–4 µg/mL and 0.25–16 µg/mL for posaconazole, respectively. The least resistance for adhered cells was observed for posaconazole (55.8%), followed by voriconazole (62.8%) and itraconazole (88.4%). The mature biofilm of M. pachydermatis showed 100% resistance to itraconazole, 95.3% to posaconazole and 83.7% to voriconazole. The results of this study show that higher concentrations of commonly used antifungal agents are needed to control infections caused by biofilm-forming strains of M. pachydermatis.

Unveiling the hidden players: exploring the role of gut mycobiome in cancer development and treatment dynamics

“…Some Malassezia species such as Malassezia pachydermatis and Malassezia furfur are also found to be able to form biofilms in vitro, and these biofilms also possess the ability of pathogenesis and drug resistance. 80 , 81 Aspergillus , 82 Cryptococcus , 83 and many other fungi also possess the ability to form biofilms and act differently on the pathological process.…”

In Vitro Activity of Farnesol against Malassezia pachydermatis Isolates from Otitis Externa Cases in Dogs

“…The mechanisms of the transition of M. pachydermatis from a commensal to a pathogen are not fully understood. Generally, treatment of Malassezia -associated diseases is based on topical application of an antifungal drug combined with antibiotics to control bacterial infection and glucocorticoids to reduce inflammation [ 3 , 4 , 5 ].…”