In Vitro Susceptibility of Environmental Isolates of Exophiala dermatitidis to Five Antifungal Drugs

Abstract

Several dematiaceous fungi frequently isolated from nature are involved in cases of superficial lesions to lethal cerebral infections. Antifungal susceptibility data on environmental and clinical isolates are still sparse despite the advances in testing methods. The objective of this study was to examine the activities of 5-flucytosine, amphotericin B, itraconazole, voriconazole and terbinafine against environmental isolates of Exophiala strains by minimum inhibition concentration (MIC) determination. The strains were obtained from hydrocarbon-contaminated soil, ant cuticle and fungal pellets from the infrabuccal pocket of attine gynes. Broth microdilution assay using M38-A2 reference methodology for the five antifungal drugs and DNA sequencing for fungal identification were applied. Terbinafine was the most active drug against the tested strains. It was observed that amphotericin B was less effective, notably against Exophiala spinifera, also studied. High MICs of 5-flucytosine against Exophiala dermatitidis occurred. This finding highlights the relevance of studies on the antifungal resistance of these potential opportunistic species. Our results also contribute to a future improvement of the standard methods to access the drug efficacy currently applied to black fungi.

Combination of Amphotericin B and Terbinafine against Melanized Fungi Associated with Chromoblastomycosis

“…The three species of Fonsecaea showed similar degrees of susceptibility. As in previous reports (39)(40)(41), in our study, E. spinifera and V. botryosa were resistant to terbinafine and amphotericin B when used alone. Although a synergistic interaction was found in a combination setting for E. spinifera, the combination of terbinafine and amphotericin B exhibited an indifferent interaction for tested isolates of Veronaea botryosa.…”

Emerging pathogen in immunocompromised hosts: Exophiala dermatitidis mycosis in graft‐versus‐host disease

“…dermatitidis , there are no established minimum inhibitory concentration (MIC) breakpoints to interpret susceptibility results in a standardized fashion. Among widely used antifungal agents, itraconazole, posaconazole, and voriconazole are known to exhibit in vitro activity . The triazoles typically demonstrate lower MIC compared to amphotericin, and sufficient MIC data for the echinocandins are lacking .…”

“…Among widely used antifungal agents, itraconazole, posaconazole, and voriconazole are known to exhibit in vitro activity . The triazoles typically demonstrate lower MIC compared to amphotericin, and sufficient MIC data for the echinocandins are lacking . All of the 3 aforementioned triazoles have been used with various rates of success in previously reported cases of systemic or localized Exophiala species infection, with or without surgical intervention .…”

“…Therefore, combination therapy, other than amphotericin and flucytosine, may be considered for E. dermatitidis , although an advantage against monotherapy with amphotericin or a triazole has not been shown. In one of the few in vitro studies, the combination of terbinafine with amphotericin resulted in improved MIC for the polyene drug . Finally, in vitro activity of colistin against Exophiala species has been demonstrated, and the use of this agent has been suggested in cystic fibrosis patients with pulmonary infection .…”

The bright future of darkness—the rising power of black fungi: black yeasts, microcolonial fungi, and their relatives

“…Clinical practice may profit from the development of diagnostic molecular methods like those of Hamzehei et al [7], Badali et al [8], and Santos et al [9], while knowledge generated by Figel et al [5] is significant to hospital hygiene. Duarte et al [10] study the antifungal susceptibility of environmental species that may also be found as opportunists in human tissue. New and improved treatment options are discussed by Siqueira et al [11] and Queiroz-Telles and Santos [12].…”