A novel dermatophyte relative, Nannizzia perplicata sp. Nov., isolated from a case of tinea corporis in the United Kingdom

Abstract

A novel dermatophyte was isolated from skin scales of a female patient presenting with tinea corporis of the wrist and arm. Her principal risk factor was long-term corticosteroid use for underlying Lupus autoimmune syndrome. Microscopic examination of skin scales from lesions revealed hyphae consistent with dermatophyte infection, and a morphologically identical fungus grew in pure culture on all cultures of skin scales. Repeat isolation of the same organism from persistent lesions five months later confirmed the novel species as the causative agent. Microscopic examination revealed predominantly smooth, thin-walled macroconidia, with large numbers of unicellular aleuriospores of varied shapes and sizes. Since the isolate exhibited considerable microscopic pleomorphism, sharing morphological features consistent with several dermatophyte genera, it was subjected to multi-locus phylogenetic analyses employing a total of six different loci. Sequence analyses of all loci revealed that the isolate clustered with species within Nannizzia but diverged from all known members of the genus by 2 to 13% depending on locus analyzed. The isolate exhibited high minimum inhibitory concentrations for terbinafine in vitro, which might explain why the infection had failed to respond to two cycles of oral treatment with this antifungal agent. Interestingly, sequences in GenBank of an unnamed “Microsporum sp” isolated from leg skin of a patient in the Czech Republic showed greater than 99% identity across all of the loci analysed in common, indicating that this novel organism, which we describe here as Nannizzia perplicata sp. nov., is likely not restricted to the UK.