Introduction: Fusarium species are common soil saprophytes and plant pathogens. Members of the genus have been frequently reported as etiologic agents of opportunistic infections in humans and animals. We report six cases of confirmed or suspected onychomycosis caused by members of the genus Fusarium (F. solani and F. oxysporum species complexes).
Material and methods: The isolates were identified by rDNA ITS sequencing analysis. The EMBL accession numbers for the ITS are HE974453-HE974458. A disk diffusion method was used for in vitro susceptibility testing. Comparison of disks (ITEST) and Neo-Sensitabs tablets (Rosco) on a different media at two different temperatures (25 °C and 35 °C) was made.
Results: Six strains of Fusarium spp. (4 strains of F. solani and 2 strains of F. oxysporum) were isolated from patients with confirmed or suspected onychomycosis. Natamycin (pimaricin) was the only antifungal effective in vitro in all isolates tested. Variable susceptibility of the isolates was detected in amphotericin B, econazole and terbinafine. The remaining antifungals tested were not effective. The results varied depending on the culture medium and temperature for nystatin and econazole disks and amphotericin B and terbinafin tablets.
Conclusion: It is important to adhere to recommended methods when testing in vitro susceptibility to antifungals in moulds. An incubation temperature of 35 °C is important for obtaining valid results in amphotericin B tablets (and probably also terbinafine ones). Determination of multidrug-resistant Fusarium spp. in onychomycosis make the choice of therapy difficult. Good clinical effect was recorded with nail plate ablation and subsequent local econazole therapy.