The Drug Susceptibility of Aspergillus Species Isolated from the Patients with Onychomycosis to Itraconazole, Voriconazole, and Amphotericin B

Nowadays, the prevalence of onychomycosis caused by non-dermatophyte molds is increasing. As Aspergillus is the most common etiologic agents of the disease, this study was performed to evaluate the susceptibility of clinical isolates of Aspergillus as the cause of onychomycosis to itraconazole, voriconazole, and amphotericin B.

This cross-sectional study was performed on 50 Aspergillus strains isolated from the patients with onychomycosis referred to diagnostic laboratories of university hospitals in Mashhad, Iran. According to the phenotypic and molecular analysis of Aspergillus isolates, the most frequent species was Aspergillus flavus (A. flavus) with 34 cases. The drug susceptibility test was performed according to Clinical and Laboratory Standards Institute-M38-A2 (CLSI-M38-A2) protocol, and the minimum inhibitory concentration (MIC) of the drugs was determined.

From 50 patients with dystrophic nails, 13 were men and 37 were women. 15 patients had fungal infection of fingernails, and 33 patients had fungal infection on toenails; 2 patients had both infections of finger and toe nails. 14.7% of A. flavus isolates with MIC > 2 μg/ml to amphotericin B were considered as resistant clinical isolates. The sensitivity to itraconazole and voriconazole was 100%. MIC90 of amphotericin B, itraconazole, and voriconazole were obtained by broth microdilution method for A. flavus species as 4, 0.25, and 1 μg/ml, respectively. Significant difference was observed in MIC between itraconazole and amphotericin B (P < 0.050).

All Aspergillus species are susceptible to itraconazole and voriconazole, and these two drugs are more effective than amphotericin B on Aspergillus species. Due to the different susceptibility of these species to antifungal agents, it is necessary to perform drug susceptibility testing in order to select the appropriate drug.