Unusual dermatomycoses caused by Nannizzia nana: the geophilic origin of human infections

Abstract

Background: Fungal infections of the skin, hair, and nails are the largest and most widespread group of all mycoses. Nannizzia nana is a relatively rare etiological factor of dermatomycosis in humans, as it usually affects animals, e.g. pigs and boars. In addition to the zoophilic nature, there are also reports of the geophilic reservoir of this dermatophyte species.

Objective: In this study, we present symptomatic infections with N. nana aetiology in humans reported recently in Poland. Interestingly, these cases had a non-specific clinical picture and occurred as skin lesions on the neck and foot as well as onychomycosis of the toenails. From the medical history, the patients had no contact with pigs.

Methods: Diagnostics of these infections was performed with a combination of classical phenotypic and molecular genomic methods. The genomic diversity of the isolates was determined using the MP-PCR method. In vitro antifungal susceptibility tests against itraconazole, ketoconazole, terbinafine and naftifine hydrochloride were also performed.

Results: Nannizzia nana has been identified as an etiological factor of dermatomycosis. Moreover, heterogeneity of the genomes was revealed for the obtained strains. In vitro activities of antifungal agents showed that isolates were susceptible to all tested drugs. The patients were treated with oral terbinafine and topical ketoconazole cream, which led to a complete recovery.

Conclusions: In conclusion, the cases studied by us may indicate that the infrequency of N. nana infections may not necessarily be related to the low infectivity of this fungal agent, but they are rather associated with misdiagnosis. Furthermore, N. nana reservoirs should also be sought in soil.

Keywords: Diagnostics; Genetic diversity; Nannizzia nana; Onychomycosis; Superficial infection.

Fig. 1

Changes in human skin during infection with Nannizzia nana (camera: Nikon D3300, lens Nikon 18–105 mm VR). a In the man; b in the 41-year-old woman; c in the 75-year-old woman

Fig. 2

Micro- and macroscopic morphology of isolated dermatophytes, Nikon Coolpix YS100). a Obverse of Nannizzia nana isolate; b reverse of Nannizzia nana isolate; c positive reaction on Dermatophyte Test Medium; d micromorphology, arrows indicate characteristic macroconidia (magnification 400×); d’ macroconidia stained with lactophenol blue (magnification 1000×)

Fig. 3

Electrophoretic profile obtained with MP-PCR fingerprinting methods in 3% agarose gel. M-Molecular weight marker A&A Biotechnology (100–1000 bp), NN—strain isolated from the man, NN1—strain isolated from the 41-year-old woman, NN2—strain isolated from the 75-year-old woman