Molecular identification, biofilm formation and antifungal susceptibility of Rhodotorula spp.

Luliconazole is an imidazole antifungal agent used in topical form for the treatment of onychomycosis and dermatophytosis. In vitro activity of luliconazole against dermatophytes, Candida, black fungi, Fusarium and Aspergillus species have been investigated. Rhodotorula spp. are environmental yeasts and emerged as opportunistic pathogens among immunocompromised patients. Rhodotorula's human infections are usually resistant to treatment with antifungal drugs especially triazoles and echinocandins. The present study aimed at the molecular detection of environmental isolates of Rhodotorula spp. Then, antifungal efficacy of luliconazole was evaluated against isolates and compared to other routine systemic antifungals including; caspofungin, posaconazole, fluconazole, itraconazole, amphotericin B, and voriconazole. The biofilm production of Rhodotorula isolates was also evaluated. In this study, 39 isolates of Rhodotorula spp. were isolated from the environment, detected using molecular methods, and tested against luliconazole. Then, the anti-fungal activity of luliconazole compared with several routine antifungals. Also, biofilm formation by using a crystal violet staining assay was performed. Our finding showed that luliconazole has a very high minimum inhibitory concentration (MIC) value (1-8 µg/ml) against Rhodotorula spp. Besides, 100% of Rhodotorula strains were resistant to caspofungin, followed by fluconazole 94.7% and voriconazole 74.4%. Amphotericin B was demonstrated excellent in vitro activity against this genus. Our result indicated that 59% of Rhodotorula spp. were in the mid-range of biofilm production. Our results indicated that luliconazole does not effective against the genus Rhodotorula. Furthermore, amphotericin B is the best drug against this genus in comparison to caspofungin and other azole drugs.