Susceptibility of Clinically Relevant Filamentous Fungi to New Antifungal Drugs

Abstract

This study aims to give clear information about the in vitro susceptibility profiles of members of two important groups of pathogenic fungi (Zygomycetes and dermatophytes) isolated from Egyptian patients in previous works (Zaki et al., 2009 and Zaki et al., 2014) against 11 antifungal agents using the standard methods to improve the treatment options and to help in the control and management of fungal diseases in Egypt. - A total of ten Zygomycetes strains of clinical origin were tested for their susceptibility to some selected antifungal agents. The test strains included 3 R. oryzae strains, 3 L. ramosa strains, 1 L. corymbifera strain, 2 S. racemosum, and 1 Rh. pusillus strain. -A total of nine dermatophytes strains of clinical origin were tested for their susceptibility to some selected antifungal agents. The test strains included: 1 M. canis, 1 T. tonsurans, 2 T. rubrum, 1 T.mentagrophytes, 1 T.violaceum, 1 Arthroderma sp., and 2 E. floccosum strains. 179 Chapter IV - The antifungals used were Amphotericin B, Itraconazole, Voriconazole, Fluconazole, Terbinafine, Ketoconazole, Griseofulvin, Caspofungin, Micafungin, Posaconazole and Flucytosine. - The standard methods of susceptibility testing to antifungal drugs were used. The broth microdilution method, The disk diffusion method, and the E-test method. - Members of the three families belongs to Order Mucorales (Zygomycetes) tested were fully susceptible to Amphotericin B and Itraconazole and completely resistant to Voriconazole, Griseofulvin, Flucytosine, Caspofungin, and Micafungin. A considerable variation of susceptibility to Fluconazole, Ketoconazole, Terbinafine and Posaconazole were detected. Mucoraceae members showed reduced susceptibility to Fluconazole and Ketoconazole and a lack of activity of Terbinafine and Posaconazole. Lichtheimiaceae members were characterized by susceptibility to Ketoconazole and reduced susceptibility to Fluconazole, Terbinafine, and Posaconazole. 180 Chapter IV Syncephalastraceae members were characterized by susceptibility to Ketoconazole, Posaconazole but showed reduced susceptibility to Fluconazole and resistance to Terbinafine. - Dermatophytes tested strains were fully susceptible to Voriconazole, Itraconazole, Ketoconazole, and Griseofulvin. Amphotericin B and Fluconazole showed the lowest activity. A high range of MICs was obtained for Terbinafine in this study, while Flucytosine was completely inactive. The Echinocandins (Caspofungin and Micafungin) showed good activity against the dermatophytes strains and could be used as alternative drugs for dermatophytoses treatment.