Insights into Changing Dermatophyte Spectrum in India Through Analysis of Cumulative 161,245 Cases Between 1939 and 2021

Molecular Epidemiology and Clinical Aspects of Dermatophytosis in Guiyang, Southwest China (2017-2023): A Single-Institution Retrospective Study

Epidemiological studies combining taxonomic and clinical data have been limited globally, particularly Guiyang, the most under-developed economic provincial capital city in southwestern China. A retrospective analysis was performed of dermatophyte epidemiology involving all culture-positive cases received between May 2017 and May 2023 at the Affiliated Hospital of Guizhou Medical University. Phylogenetic analysis was conducted on 391 dermatophyte isolates collected from patients using the rDNA internal transcribed spacer sequences. Clinical relevance information was analyzed statistically using T-test, one-way ANOVA, Kruskal-Wallis H test, and Chi-square test. Eight species were recognized, and their identity was confirmed on the basis of phylogenetics. Trichophyton rubrum (n = 308, 78.77%) ranked first, followed by T. mentagrophytes (n = 39, 9.97%) and Microsporum canis (n = 32, 8.18%). Tinea unguium (48.56%) was the most common type of dermatophytosis in this study, rates of detection being impacted by the host population's attention for dermatophyte infections. The hypothesized patterns of evolution in the M. canis series, T. mentagrophytes series and T. rubrum series, i.e. from zoophilic to a preponderantly anthropophilic nature, was reflected in clinical parameters such as host age, occupational background, infection pattern, degree of skin involvement and site preference. To the best of our knowledge, we provide the first detailed analysis of epidemiological characteristics and pathogenic patterns of dermatophytosis in Guiyang.

Whole Genome Sequence Analysis of Terbinafine Resistant and Susceptible Trichophyton Isolates from Human and Animal Origin

Trichophyton indotineae, first identified in India, has increasingly been reported in Asia, the Middle East, Europe, and recently in the USA. The global spread of terbinafine-resistant T. indotineae underscores the urgency of the issue. With its ability for human-to-human transmission, it can be considered anthropophilic. However, its highly virulent nature suggests a possible link to zoophilic species, raising the potential for disease transmission from animals. In this study, we have performed whole genome sequencing (WGS) of terbinafine susceptible and resistant Trichophyton species from animal and human origin to understand transmission dynamics of this species. Thirteen isolates of Trichophyton spp. from human (n = 9) and canine (n = 4) origin, respectively from Chandigarh and Bareilly, India, were included in this study. Isolate identification based on ITS extracted from WGS data identified six T. indotineae (ITS genotype VIII) and seven T. interdigitale (ITS genotype II) isolates. WGS single nucleotide polymorhpism (SNP) analysis separated the isolates into two distinct groups, T. indotineae and T. interdigitale and showed the clonal nature of both species. For both species, low SNP differences between isolates from humans and dogs were observed as well as low differences between isolates from Chandigarh and Bareilly, cities >350 km apart from each other. These findings suggest zoonotic transmission, next to fast spread across large distances. The T. indotineae terbinafine-resistant strains exhibited the SQLEF397L substitution while susceptible strains had the SQLES395P substitution or demonstrated a wild-type (WT) SQLE sequence. However, all T. interdigitale strains displayed a WT SQLE sequence despite terbinafine minimum inhibitory concentrations (MICs) ranging between 0.031 to 64 µg/mL.

Emerging Antifungal Resistance in Trichophyton mentagrophytes: Insights from Susceptibility Profiling and Genetic Mutation Analysis

Trichophyton species, the leading cause of dermatophytosis globally, are increasingly resistant to antifungal treatments, concerns about effective management strategies. In light of the absence of established resistance criteria for terbinafine and azoles, coupled with a dearth of research on resistance mechanisms in Trichophyton, antifungal susceptibility and drug resistance gene diversity were analyzed across 64 T. mentagrophytes, 65 T. interdigitale, and 2 T. indotineae isolates collected in China between 2001 and 2024 and 101 published T. indotineae strains. Analyses of the minimum inhibitory concentrations (MICs) of terbinafine, itraconazole, voriconazole, posaconazole, and isavuconazole revealed a concerning increase in T. indotineae with terbinafine resistance, including two novel isolates from China. Compared with T. interdigitale, T. mentagrophytes presented higher terbinafine MICs but similar azole susceptibility. Notably, 27 T. interdigitale isolates were classified as non-wild-type for terbinafine. Genetic diversity was analyzed for the SQLE, CYP51A and CYP51B gene. Specifically, T. indotineae isolates presented SQLE protein changes linked to terbinafine resistance. SQLE diversity was linked to terbinafine sensitivity, whereas alterations in CYP51A were associated with itraconazole sensitivity, with notable statistical significance evident across various protein isoforms. The relationship between protein diversity and drug sensitivity is presented in detail. Together, these findings highlight a growing prevalence of antibiotic resistance among Trichophyton and identify potential target genes for new therapies, underscoring the need for ongoing monitoring and offering directions for novel therapeutics.

Trichophyton mentagrophytes ITS Genotype VIII/Trichophyton indotineae Infection and Antifungal Resistance in Bangladesh

Trichophyton (T.) mentagrophytes ITS genotype VIII, also known as Trichophyton indotineae, is a new species of the T. mentagrophytes/T. interdigitale complex and its first records, albeit under a different species name, are from the Indian subcontinent, Middle Eastern Asia, and West Asia. T. mentagrophytes genotype VIII (T. indotineae) has spread globally and has now been documented in over 30 countries. The aim of this study was to investigate the occurrence and proportion of terbinafine- and itraconazole-resistant isolates of T. mentagrophytes ITS genotype VIII (T. indotineae) in Bangladesh. This was part of an official collaborative project between IADVL (Indian Association of Dermatologists, Venereologists, and Leprologists) and Bangabandhu Sheikh Mujib Medical University (BSMMU), Bangladesh. Over a period of 6 months, ninety-nine patients of chronic recalcitrant tinea corporis were recruited from BSMMU hospital. Species identification was performed by fungal culture and morphological observation of the upper and lower surfaces of fungal colonies, as well as by using fluorescent microscopy. In addition, a PCR (polymerase chain reaction)-ELISA was performed to group the patients into those with the T. mentagrophytes/T. interdigitale complex. The internal transcribed spacer (ITS) gene was sequenced. Samples were tested for resistance to terbinafine and itraconazole by mutational analyses of the squalene epoxidase (SQLE) and the ergosterol 11B (ERG11B) genes. A total of 79/99 samples showed a positive culture. In 76 of these isolates, T. mentagrophytes ITS genotype VIII (T. indotineae) could be reliably identified both by culture and molecular testing. Resistance testing revealed terbinafine resistance in 49 and itraconazole resistance in 21 patients. Among these, 11 patients were resistant to both the antifungal agents. Mutations L393S, L393F, F397L, and F397I of the SQLE gene were associated with terbinafine resistance. Resistance to itraconazole could not be explained by mutations in the ERG11B gene. Infections with T. mentagrophytes ITS genotype VIII (T. indotineae) have become a public health issue with potentially global ramifications. About 62% of samples from Bangladesh showed resistance to terbinafine, making oral itraconazole the most effective drug currently available, although resistance to itraconazole and both terbinafine and itraconazole also exists.

Global Insights and Trends in Research on Dermatophytes and Dermatophytosis: A Bibliometric Analysis

BACKGROUND

Dermatophytosis, caused by dermatophytes, affects up to 25% of people globally, with higher rates observed in Africa and Asia. While these infections are usually superficial, they can become severe in immunocompromised individuals. Despite their high prevalence, scientific research on dermatophytes is limited and the epidemiological data available are insufficient. In addition, diagnostic methods are not standardised and there are challenges with resistance to antifungals.

OBJECTIVES

This study aimed to conduct a bibliometric analysis of scientific publications related to dermatophytes and dermatophytosis to assess research output and trends.

METHODS

A bibliometric analysis of publications from 2000 to 2023 in Web of Science and Scopus examined trends, citation counts, publication types, key journals, top authors and institutions and funding sources.

RESULTS

The analysis revealed a significant increase in dermatophyte-related publications, with 15,868 articles retrieved from the Web of Science and 23,189 from Scopus. Research articles dominated the output, constituting 76.2% in Web of Science and 80% in Scopus. Peak publication years were 2019, 2021 and 2022 in Web of Science, and 2020, 2021 and 2023 in Scopus, with lower output between 2000 and 2002. The United States and India were the leading contributors, followed by Brazil and China, though citation metrics varied. Although there has been a rise in the number of publications, the amount of research conducted on dermatophytes is still very limited in comparison with other types of fungal diseases.

CONCLUSIONS

Dermatophyte-related research has increased over the past 2 decades. However, research gaps remain, particularly compared with other fungal diseases. Advances in diagnostics, antifungal testing and taxonomic classification are urgently needed. The study underscores the need for continued research and global collaboration to address these issues.

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.

The Impact of the Fungal Priority Pathogens List on Medical Mycology: A Northern European Perspective

Fungal diseases represent a considerable global health concern, affecting >1 billion people annually. In response to this growing challenge, the World Health Organization introduced the pivotal fungal priority pathogens list (FPPL) in late 2022. The FPPL highlights the challenges in estimating the global burden of fungal diseases and antifungal resistance (AFR), as well as limited surveillance capabilities and lack of routine AFR testing. Furthermore, training programs should incorporate sufficient information on fungal diseases, necessitating global advocacy to educate health care professionals and scientists. Established international guidelines and the FPPL are vital in strengthening local guidance on tackling fungal diseases. Future iterations of the FPPL have the potential to refine the list further, addressing its limitations and advancing our collective ability to combat fungal diseases effectively. Napp Pharmaceuticals Limited (Mundipharma UK) organized a workshop with key experts from Northern Europe to discuss the impact of the FPPL on regional clinical practice.

Whole genome characterization of Trichophyton indotineae isolated in Singapore

Complete genome sequences from two Trichophyton indotineae isolates were obtained from a 23-year-old male presenting with tinea cruris after an overseas recreational water exposure and from a 53-year-old female patient with unknown travel history. Analysis of the squalene epoxidase gene and the cyp51 gene family showed an absence of mutations, correlating with phenotypic drug susceptibility. The Single Nucleotide Polymorphisms (SNPs) distance between both isolates was 92. Within the T. indotineae cluster, SNPs ranged from 7 to 182, suggesting a high genetic relatedness with other South Asian isolates. This study suggests that the prevalence of T. indotineae is under-reported and more widespread than previously thought.

Molecular typing of a collection of Iranian clinical Trichophyton tonsurans isolates based on the non-transcribed spacer region of rDNA and antifungal susceptibility testing of the species

INTRODUCTION

Wrestling, considered the national sport of Iran, has gained immense popularity among Iranians. Wrestlers frequently encounter skin conditions, with dermatophyte fungal infections, particularly tinea gladiatorum (TG), being a common issue. TG, caused by the Trichophyton genus, has emerged as a major health concern for wrestlers and other contact sport athletes worldwide. This study aimed to assess the genotypic diversity and antifungal susceptibility of Trichophyton tonsurans isolates responsible for TG in Iranian wrestlers from Mazandaran province, northern Iran.

MATERIALS AND METHODS

A total of 60 clinical T. tonsurans isolates collected from various cities in Mazandaran, were included in the study. The isolates were identified through PCR-restriction fragment length polymorphism and sequencing methods. Genomic DNA was extracted from these isolates, and the non-transcribed spacer (NTS) region of ribosomal RNA (rRNA) was targeted for genotyping using newly designed primers. Haplotype analysis was performed to explore genetic diversity, and antifungal susceptibility to terbinafine (TRB) and itraconazole (ITC) was assessed.

RESULTS

The results revealed five distinct NTS types: NTS-I, NTS-II, NTS-III, NTS-IV and NTS-V, with NTS-IV being the most prevalent. The distribution of NTS types varied across different cities, suggesting potential transmission patterns among wrestlers. Antifungal susceptibility testing showed that all isolates were susceptible to TRB, while one isolate demonstrated resistance to ITC. Genotypic diversity was not correlated with antifungal susceptibility, emphasising the importance of monitoring susceptibility to ensure effective treatment. Haplotype analysis highlighted significant genetic diversity among the T. tonsurans isolates. This diversity may be attributed to factors such as human-to-human transmission, geographic location and lifestyle changes. The study's findings underscore the need for comprehensive genotypic analysis to understand the epidemiology and evolution of T. tonsurans infections in athletes.

CONCLUSION

In conclusion, this study provides valuable insights into the genotypic diversity and antifungal susceptibility of T. tonsurans isolates causing TG in Iranian wrestlers. The presence of multiple NTS types and varying susceptibility patterns highlights the complexity of T. tonsurans infections in this population. Further research is warranted to track the transmission routes and genetic evolution of T. tonsurans strains among wrestlers and develop effective control measures.

Dermatophyte infection: from fungal pathogenicity to host immune responses

Dermatophytosis is a common superficial infection caused by dermatophytes, a group of pathogenic keratinophilic fungi. Apart from invasion against skin barrier, host immune responses to dermatophytes could also lead to pathologic inflammation and tissue damage to some extent. Therefore, it is of great help to understand the pathogenesis of dermatophytes, including fungal virulence factors and anti-pathogen immune responses. This review aims to summarize the recent advances in host-fungal interactions, focusing on the mechanisms of anti-fungal immunity and the relationship between immune deficiency and chronic dermatophytosis, in order to facilitate novel diagnostic and therapeutic approaches to improve the outcomes of these patients.