Different Genes Can Result in Different Phylogenetic Relationships in Trichophyton Species

Recalcitrant dermatophyte infections: identification and risk factors

INTRODUCTION

Recalcitrant dermatophytosis is an emerging phenomenon that occurs worldwide, and Trichophyton indotineae is currently the prominent cause.

MATERIALS AND METHODS

Skin specimens from patients with tinea infection were obtained by scrubbing and then sectioned into three fragments. Two fragments were subjected to direct microscopic examination and culture, while the third portion was utilized in the PCR method.

RESULTS

Isolates were morphologically identified as Trichophyton mentagrophytes/interdigitale complex (n = 60 [83.33%]), Microsporum canis (n = 8 [11.11%]), Trichophyton rubrum (n = 3 [4.16%]), and Epidermophyton floccosum (n = 1 [1.38%]). Among 60 T. mentagrophytes complex isolates, 53 (88.33%) were classified as T. indotineae and seven as T. interdigitale genotype II. The disease duration was longer in the T. indotineae group (P = 0.035). Both Gradient PCR and skin-sampling methods yield similar results in terms of positive and negative cases (P = 1.0000). The time patients stopped their medication did not impact the positive case numbers (P = 0.803). Gender had no effects on the frequency (P = 0.699). Familial contamination, dermatologic disorder, and other underlying conditions did not differ in the two group infections (P > 0.05). Steroid usage is strongly associated with the emergence of tinea infection (P < 0.04). The duration of antifungal administration had a substantial effect on the emergence of resistant organisms (P = 0.05).

CONCLUSIONS

Steroid usage, T. indotineae involvement, and prolonged exposure to antifungals were the solid and influential factors in recalcitrant involvement. Regarding quick and suitable diagnosis and treatment, which is essential in preventing recalcitrant cases, we suggest that direct skin sample PCR can meet the demands.

A Comparative Description of Dermatophyte Genomes: A State-of-the-Art Review

The nomenclature and phylogeny of dermatophytes is currently based on the nucleotide sequence polymorphisms of a few genomic regions. However, the limitations of this multilocus sequence-based approach makes dermatophyte species identification difficult. Variation and adaptation are key to the persistence of species. Nevertheless, this heterogeneity poses a genuine problem for the classification and nomenclature of dermatophytes. The relatively high intra-species and low inter-species polymorphisms of this keratinophilic group of fungi hampers both species delineation and identification. Establishing the taxonomic boundaries of dermatophyte species complexes remains controversial. Furthermore, until recently, knowledge of molecular biology, genetics and genomics remained limited. This systematic review highlights the added value of whole genome sequencing and analysis data in dermatophyte classification that might enhance identification and, consequently, the diagnosis and management of dermatophytoses. Our approach consisted in describing and comparing the dermatophyte mitochondrial genomes, secretomes (Adhesins, LysM domains, proteases) and metabolic pathways, with the aim to provide new insights and a better understanding of the phylogeny and evolution of dermatophytes.

A Terbinafine Sensitive Trichophyton indotineae Strain in Italy: The First Clinical Case of tinea corporis and onychomycosis

Trichophyton indotineae is an emerging dermatophyte species that plays a relevant role in human healthcare. It has been associated with severe chronic skin infections and a high level of terbinafine resistance. T. indotineae is endemic to India, Iran, and Iraq but several cases have been reported in Europe, recently. In this manuscript, the authors report the first clinical description of a tinea corporis and onychomycosis due to T. indotineae. The patient was a 42-year-old female from India that has lived in Umbria (Central Italy) for the last two years. Firstly, a dermatological examination suggested dermatophytosis: mycology isolation from cultures and macro- and microscopical features identified the colonies as belonging to the T. mentagrophytes/T. interdigitale species complex. Subsequently, ITS1/ITS4 end-point PCR and Sanger sequencing identified the strain as T. indotineae. Lastly, a DermaGenius® Resistance Multiplex real-time PCR assay was carried out, targeting the mutations in the SQLE gene to establish terbinafine resistance or susceptibility of the strain. The melting curve observed was compatible with wild-type positive control, identifying the strain as T. indotineae terbinafine-sensitive. An oral terbinafine treatment was associated with a topical ciclopirox nail solution, resulting in remission in its clinical manifestation. On 3 July 2023, the local Prevention Service notified the case to the Ministry of Health that then reported the information at national and international levels.

Trichophyton indotineae, from epidemiology to therapeutic

Trichophyton indotineae is a newly described dermatophyte species. This fungal pathogen has recently emerged in India and is responsible for chronic or recurrent widespread superficial infections. Resistance to terbinafine is frequently associated to this pathogen and is related to point mutations in the gene encoding the squalene epoxidase. T. indotineae infections have been reported outside India, highlighting the risk of worldwide diffusion of this microorganism. Species identification and antifungal susceptibility determination are key points for infection control but still remain challenging. Systemic treatment is usually required and itraconazole is frequently prescribed in case of terbinafine resistance. This review summarizes main features of T. indotineae taxonomy, epidemiology, clinical manifestations, identification, antifungal profile, treatment and prevention.

Trichophyton indotineae—An Emerging Pathogen Causing Recalcitrant Dermatophytoses in India and Worldwide—A Multidimensional Perspective

Trichophyton (T.) indotineae is a newly identified dermatophyte species that has been found in a near-epidemic form on the Indian subcontinent. There is evidence of its spread from the Indian subcontinent to a number of countries worldwide. The fungus is identical to genotype VIII within the T. mentagrophytes/T. interdigitale species complex, which was described in 2019 by sequencing the Internal Transcribed Spacer (ITS) region of ribosomal DNA of the dermatophyte. More than 10 ITS genotypes of T. interdigitale and T. mentagrophytes can now be identified. T. indotineae causes inflammatory and itchy, often widespread, dermatophytosis affecting the groins, gluteal region, trunk, and face. Patients of all ages and genders are affected. The new species has largely displaced other previously prevalent dermatophytes on the Indian subcontinent. T. indotineae has become a problematic dermatophyte due to its predominantly in vitro genetic resistance to terbinafine owing to point mutations of the squalene epoxidase gene. It also displays in vivo resistance to terbinafine. The most efficacious drug currently available for this terbinafine-resistant dermatophytoses, based on sound evidence, is itraconazole.

Tinea Imbricata among the Indigenous Communities: Current Global Epidemiology and Research Gaps Associated with Host Genetics and Skin Microbiota

Tinea imbricata is a unique fungal skin disease that mostly affects indigenous populations in Southeast Asia, Oceania, and Central and South America. The control and management of this disease among these communities are challenging given their remote locations, certain traditional practices, and severe malnutrition status. To date, there are only a handful of reports published globally, which highlights the need for a more holistic approach in addressing this skin disease. Several bodies of evidence and reports have shown that host genetic factors have a profound influence on the pathogenesis of tinea imbricata, while skin microbiota is touted to have a role in the pathogenesis of the disease. However, there are limited studies of how host genetics and skin microbiota impact disease susceptibility in the host. To improve the understanding of this disease and to find possible long-term effective treatment among the affected indigenous communities, a comprehensive literature review is needed. Hence, this review paper aims to present the current status of tinea imbricata among the indigenous communities, together with published findings on the possible underlying reasons for its specific distribution among these communities, particularly on the ways in which host skin microbiota and host genetics affect occurrence and disease patterns. This information provides valuable insights for future research by highlighting the current knowledge gaps in these areas.

Phylogenetic analysis of dermatophyte species using DNA sequence polymorphism in calmodulin gene

Use of phylogenetic species concepts based on rDNA internal transcribe spacer (ITS) regions have improved the taxonomy of dermatophyte species; however, confirmation and refinement using other genes are needed. Since the calmodulin gene has not been systematically used in dermatophyte taxonomy, we evaluated its intra- and interspecies sequence variation as well as its application in identification, phylogenetic analysis, and taxonomy of 202 strains of 29 dermatophyte species. A set of primers was designed and optimized to amplify the target followed by bilateral sequencing. Using pairwise nucleotide comparisons, a mean similarity of 81% was observed among 29 dermatophyte species, with inter-species diversity ranging from 0 to 200 nucleotides (nt). Intraspecies nt differences were found within strains of Trichophyton interdigitale, Arthroderma simii, T. rubrum and A. vanbreuseghemii, while T. tonsurans, T. violaceum, Epidermophyton floccosum, Microsporum canis, M. audouinii, M. cookei, M. racemosum, M. gypseum, T. mentagrophytes, T schoenleinii, and A. benhamiae were conserved. Strains of E. floccosum/M. racemosum/M. cookei, A. obtosum/A. gertleri, T. tonsurans/T. equinum and a genotype of T. interdigitale had identical calmodulin sequences. For the majority of the species, tree topology obtained for calmodulin gene showed a congruence with coding and non-coding regions including ITS, BT2, and Tef-1α. Compared with the phylogenetic tree derived from ITS, BT2, and Tef-1α genes, some species such as E. floccosum and A. gertleri took relatively remote positions. Here, characterization and obtained dendrogram of calmodulin gene on a broad range of dermatophyte species provide a basis for further discovery of relationships between species. Studies of other loci are necessary to confirm the results.

Molecular identification and classification of Trichophyton mentagrophytes complex strains isolated from humans and selected animal species

Species differentiation within Trichophyton mentagrophytes complex group currently poses a major diagnostic challenge, with molecular methods increasingly supplementing classical identification based on the morphological and physiological properties of the fungi. Diagnostic and epidemiological research aimed at determining the source and means of transmission of dermatophytoses in both humans and animals requires not only species differentiation of isolates but also differentiation within species. The study was conducted on 24 isolates originating in humans and various animal species with clinical symptoms of dermatophytosis. The analysis included phenotypical identification methods and molecular methods: internal transcribed spacer sequencing and ITS-restriction fragment length polymorphism (RFLP) with multi-enzyme restriction. ITS sequence analysis identified the isolates to species - Trichophyton interdigitale, Arthroderma benhamiae and A. vanbreuseghemii, and ITS-RFLP detected six different genotypes. Genotypes I, II and III characterised strains belonging to A. benhamiae, genotype IV characterised the A. vanbreuseghemii strain, and genotypes V and VI occurred only within the species T. interdigitale. Strains isolated from guinea pigs were dominant within genotype I, while genotype II was found mainly in strains from foxes. Multi-enzyme restriction analysis of this region enables intraspecific differentiation, which may be useful in epidemiological research, particularly in determining the source of infections.

Translation elongation factor 1-α gene as a potential taxonomic and identification marker in dermatophytes

Intra- and interspecies variations of the translation elongation factor 1-α (Tef-1α) gene were evaluated as a new identification marker in a wide range of dermatophytes, which included 167 strains of 30 species. An optimized pan-dermatophyte primer pair was designed, and the target was sequenced. Consensus sequences were used for multiple alignment and phylogenetic tree analysis and the levels of intra- and interspecific nucleotide polymorphism were assessed. Between species, the analyzed part of the Tef-1α gene varied in length from 709 to 769 nucleotides. Significant numbers of species including Trichophyton rubrum, T. tonsurans, T. schoenleinii, T. concentricum, T. violaceum, Epidermophyton floccosum, Microsporum ferrugineum, M. canis, M. audouinii, T. equinum, T. eriotrephon, and T. erinacei were invariant in Tef-1α and had sufficient barcoding distance with neighboring species. Although overall consistency was found between ITS phylogeny as the current molecular marker of dermatophytes and Tef-1α, a higher discriminatory power of Tef-1α appeared particularly useful in some clades of closely related species such as the A. vanbreuseghemii, T. rubrum, A. benhamiae, and A. otae complexes. Nevertheless, we stress that a single gene can not specify species borderlines among dermatophytes and multiple lines of evidence based on a multilocus inquiry may ascertain an incontrovertible evaluation of kinship.

The Improvement of the Resistance to Candida albicans and Trichophyton interdigitale of Some Woven Fabrics Based on Cotton

This paper presents the improvement of the antimicrobial character of woven fabrics based on cotton. The woven fabrics were cleaned in oxygen plasma and treated by padding with silver chloride and titanium dioxide particles. The existence of silver and titanium on woven fabrics was evidenced by electronic microscope images (SEM, EDAX) and by flame atomic absorption spectrophotometry. The antimicrobial tests were performed with two fungi: Candida albicans and Trichophyton interdigitale. The obtained antimicrobial effect was considerably higher compared to the raw fabrics. Treatment of dyed fabrics with a colloidal solution based on silver chloride and titanium dioxide particles does not considerably influence colour resistance of dyes.

Nucleotide sequence analysis of beta tubulin gene in a wide range of dermatophytes

We investigated the resolving power of the beta tubulin protein-coding gene (BT2) for systematic study of dermatophyte fungi. Initially, 144 standard and clinical strains belonging to 26 species in the genera Trichophyton, Microsporum, and Epidermophyton were identified by internal transcribe spacer (ITS) sequencing. Subsequently, BT2 was partially amplified in all strains, and sequence analysis performed after construction of a BT2 database that showed length ranged from approximately 723 (T. ajelloi) to 808 nucleotides (M. persicolor) in different species. Intraspecific sequence variation was found in some species, but T. tonsurans, T. equinum, T. concentricum, T. verrucosum, T. rubrum, T. violaceum, T. eriotrephon, E. floccosum, M. canis, M. ferrugineum, and M. audouinii were invariant. The sequences were found to be relatively conserved among different strains of the same species. The species with the closest resemblance were Arthroderma benhamiae and T. concentricum and T. tonsurans and T. equinum with 100% and 99.8% identity, respectively; the most distant species were M. persicolor and M. amazonicum. The dendrogram obtained from BT2 topology was almost compatible with the species concept based on ITS sequencing, and similar clades and species were distinguished in the BT2 tree. Here, beta tubulin was characterized in a wide range of dermatophytes in order to assess intra- and interspecies variation and resolution and was found to be a taxonomically valuable gene.

Tinea imbricata in the Americas

PURPOSE OF REVIEW

The aim is to provide an overview on tinea imbricata, or Tokelau, a superficial mycosis caused by Trichophyton concentricum, a strictly anthropophilic dermatophyte with a well-defined geographic distribution and predisposing factors that include genetic, racial and immunologic susceptibility patterns and a specific environment.

RECENT FINDINGS

This review covers the most interesting aspects of the infrequent disease tinea imbricata, including the historical background, the epidemiologic aspects, highlighting the genetic and racial patterns of susceptibility to the acquisition of the disease, and the immunologic aspects that help to explain its clinical behavior. We also present a clinical description of the disease, the differential diagnosis and how currently some other emerging diseases such as syphilis in immunocompromised patients can mimic tinea imbricata. The therapeutic options are still griseofulvin and nowadays terbinafine, but the access to the treatments in the endemic zones and the changes in habits of the affected population make control and prevention of the disease difficult.

SUMMARY

Tinea imbricata, or Tokelau, remains an infrequent superficial mycosis restricted to endemic zones in the South Pacific islands (Polynesia and Melanesia), South Asia and some specific areas of South America. Migration phenomena and global changes in the climate may modify the incidence and characteristics of the disease.

Matings among three teleomorphs of Trichophyton mentagrophytes

Three genetically hybrid F1 progenies produced between a clinical isolate of Arthroderma simii (KMU4810) and a tester strain of A. vanbreuseghemii (RV27961) were crossed with two tester strains of A. vanbreuseghemii (RV27961 and RV27960) and a tester strain of A. benhamiae (RV30001), respectively. Three crossings yielded hybrid second progenies. Another interspecies crossing between A. simii (KMU4810) and a tester strain of A. benhamiae (RV26680) yielded one hybrid F1 progeny (Asb57). The second crossings of F1 progeny (Asb57) with A. vanbreuseghemii (RV27961) and A. benhamiae (RV30001) yielded many hybrid second progenies. Some hybrid second progenies produced between F1 progeny and A. vanbreuseghemii were confirmed to have genes from three species. The gene exchangeability among three Arthroderma species was shown and the meaning of these events discussed.

Successful mating of Trichophyton rubrum with Arthroderma simii

Crossing of Trichophyton rubrum with Arthroderma simii yielded many ascomata around the fluffy T. rubrum colonies. One of the 35 supposed ascospores isolated from matured ascoma was shown to be a hybrid of the two species. Hybrids were observed within the genotypes of four different genes, i.e., rRNA, actin, DNA topoisomerase II and cytochrome b. These results strongly suggest that T. rubrum is not an asexual or clonal species.

Successful mating of a human isolate of Arthroderma simii with a tester strain of A. vanbreuseghemii

An isolate of Arthroderma simii was successfully mated with a tester strain of A. vanbreuseghemii cultured on the plate of simple agar with some hair on it at 27 degrees C. Confirmation of sexual reproduction was made by the detection of hybrids of two parental genotypes. The implications of this result are discussed from the viewpoint of a reevaluation of the species boundaries of dermatophytes.