Host-driven subspeciation in hedgehog fungus, Trichophyton erinacei, an emerging cause of human dermatophytosis

<p><span class="fontstyle0"><em>Trichophyton</em> <em>erinacei</em> </span><span class="fontstyle2">is a main cause of dermatophytosis in hedgehogs and is increasingly reported from human infections worldwide. This pathogen was originally described in the European hedgehog (</span><em><span class="fontstyle0">Erinaceus europaeus</span></em><span class="fontstyle2">) but is also frequently found in the African four-toed hedgehog (</span><em><span class="fontstyle0">Atelerix albiventris</span></em><span class="fontstyle2">), a popular pet animal worldwide. Little is known about the taxonomy and population genetics of this pathogen despite its increasing importance in clinical practice. Notably, whether there are different populations or even cryptic species associated with different hosts or geographic regions is not known. To answer these questions, we collected 161 isolates, performed phylogenetic and population-genetic analyses, determined mating-type, and characterised morphology and physiology. Multigene phylogeny and microsatellite analysis supported </span><span class="fontstyle0"><em>T</em>. <em>erinacei</em> </span><span class="fontstyle2">as a monophyletic species, in contrast to highly incongruent single-gene phylogenies. Two main subpopulations, one specific mainly to </span><span class="fontstyle0"><em>Atelerix</em> </span><span class="fontstyle2">and second to </span><span class="fontstyle0"><em>Erinaceus</em> </span><span class="fontstyle2">hosts, were identified inside </span><span class="fontstyle0">T. <em>erinacei</em></span><span class="fontstyle2">, and slight differences in the size of microconidia and antifungal susceptibilities were observed among them. Although the process of speciation into two lineages is ongoing in </span><em><span class="fontstyle0">T. erinacei</span></em><span class="fontstyle2"><em>,</em> there is still gene flow between these populations. Thus, we present </span><span class="fontstyle0"><em>T</em>. <em>erinacei</em> </span><span class="fontstyle2">as a single species, with notable intraspecies variability in genotype and phenotype. The data from wild hedgehogs indicated that sexual reproduction in </span><span class="fontstyle0"><em>T</em>. <em>erinacei</em> </span><span class="fontstyle2">and de novo infection of hedgehogs from soil are probably rare events and that clonal horizontal spread strongly dominates. The molecular typing approach used in this study represents a suitable tool for further epidemiological surveillance of this emerging pathogen in both animals and humans. The results of this study also highlighted the need to use a multigene phylogeny ideally in combination with other independent molecular markers to understand the species boundaries of dermatophytes.</span></p>