Fusarium spp. as agents of onychomycosis in immunocompetent hosts

Background Fusarium spp. are nondermatophyte filamentous fungi, frequently reported as an etiologic agent of opportunistic infections in humans; however, their involvement in the etiology of cutaneous lesions is still debatable, especially in immunocompetent patients, where they are often considered as contaminant fungi. Objective The aims of this study were to report the high prevalence of onychomycosis by Fusarium spp. in immunocompetent patients in the region of Maringa, Parana, Brazil, to establish clinical and laboratory criteria for this genus as a causal agent of onychomycosis, and to determine the susceptibility profile to the systemic antifungal drugs most frequently used in Brazil (itraconazole, ketoconazole, terbinafine, and amphotericin B). Methods The fungi were isolated and identified through the classical method, and sensitivity tests were carried out according to the National Committee for Clinical Laboratory Standards (NCCLS) M38-A protocol. Results Of the 360 confirmed cases of onychomycosis, 27 (7.5%) were attributed to the genus Fusarium, and F oxysporum was the most commonly isolated species. Nail lesions with paronychia and pain, combined with direct suggestive microscopy and a high concentration of microorganisms, were predictive of onychomycosis by Fusarium spp. The minimum inhibitory concentration was high for itraconazole, ketoconazole, and terbinafine, but low for amphotericin B. Conclusions It is recommended that more attention should be given to the interpretation and identification of species of the Fusarium genus in superficial clinical samples. This fungus may be considered as an agent of onychomycosis, even in immunocompetent individuals, by identifying criteria that separate situations of clinical significance from those of simple contamination.