Strain Differentiation of Dermatophytes

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.

Clonal Outbreak of Trichophyton tonsurans Causing Tinea Capitis Among a Wrestling Team in Beijing, China

Trichophyton tonsurans mostly causes tinea capitis and tinea corporis and often associates with outbreaks among combat sports athletes. Here, we report an outbreak of tinea capitis caused by T. tonsurans among five juvenile athletes in a wrestling team in Beijing, China. Scrapings from the lesions of the five patients were performed by direct microscopic examination and fungal culture. The fungal pathogens were all identified as T. tonsurans by morphology and sequencing of the internal transcribed spacer (ITS) regions. Multilocus genotyping analysis was performed by sequencing of 13 gene loci. The sequences of these markers were identical among the five isolates, revealing a single genotype. Antifungal susceptibilities of terbinafine, itraconazole, fluconazole, ketoconazole, and amphotericin B against T. tonsurans was determined by broth microdilution method according to the Clinical and Laboratory Standards Institute M38-A3 document and these isolates were all susceptible to the common antifungal drugs treating tinea capitis.

Phenotypic and Genotypic Identification of Dermatophytes from Mexico and Central American Countries

Dermatophytes are fungi included in the genera Trichophyton, Microsporum, Epidermophyton, Nannizzia, Paraphyton, Lophophyton, and Arthroderma. Molecular techniques have contributed to faster and more precise identification, allowing significant advances in phylogenetic studies. This work aimed to identify clinical isolates of dermatophytes through phenotypic (macro- and micromorphology and conidia size) and genotypic methods (sequences of ITS regions, genes of β tubulin (BT2), and elongation factor α (Tef-1α)) and determine the phylogenetic relationships between isolates. Ninety-four dermatophyte isolates from Costa Rica, Guatemala, Honduras, Mexico, and the Dominican Republic were studied. The isolates presented macro- and micromorphology and conidia size described for the genera Trichophyton, Microsporum, and Epidermophyton. Genotypic analysis classified the isolates into the genera Trichophyton (63.8%), Nannizzia (25.5%), Arthroderma (9.6%), and Epidermophyton (1.1%). The most frequent species were T. rubrum (26 isolates, 27.6%), T. interdigitale (26 isolates, 27.6%), and N. incurvata (11 isolates, 11.7%), N. gypsea and A. otae (nine isolates, 9.6%), among others. The genotypic methods clarified the taxonomic status of closely related species. For instance, the ITS and BT2 markers of T. rubrum/T. violaceum did not differ but the Tef-1α gene did. On the other hand, the three markers differed in T. equinum/T. tonsurans. Therefore, the ITS, BT2, and Tef-1α genes are useful for typing in phylogenetic analyses of dermatophytes, with Tef-1α being the most informative locus. It should be noted that isolate MM-474 was identified as T. tonsurans when using ITS and Tef-1α, but when using BT2, it was identified as T. rubrum. On the other hand, no significant difference was found when comparing the methods for constructing phylogenies, as the topologies were similar.

Epidemiologic features and risk of scarring in pediatric patients with kerion celsi

BACKGROUND

Kerion celsi represents the inflammatory extreme of tinea capitis, as a delayed hypersensitivity reaction to the causative dermatophyte. Data regarding prevalence, trends in pathogens, and risk factors for scarring are limited.

OBJECTIVE

The main objective of the study is to assess clinical and epidemiologic features of children with kerion celsi and risk factors for scarring.

METHODS

We reviewed medical records of pediatric patients with kerion celsi treated between January 2006 and July 2020.

RESULTS

Among 80 patients, the prevalence of permanent alopecia was 27.5%. Patients with remaining alopecia presented to our clinic at a mean 1.3 months earlier than those with complete response to treatment (2.2 ± 2.1 and 3.4 ± 4.8, respectively; p < .05). Patients of Ethiopian ethnicity were more represented than in the general population; however, scarring was observed in only 11% (p = 0.08). Outcomes did not differ by pathogen, antifungal treatment prescribed, duration of treatment, or the use of prednisone or antibiotics.

CONCLUSIONS

Scarring alopecia is a common complication of kerion celsi. Host innate immune response, pathogen virulence, and treatment timeline should be considered as possible variables affecting risk of scarring in the future studies.

Subtyping Options for Microsporum canis Using Microsatellites and MLST: A Case Study from Southern Italy

Microsporum canis is considered one of the most common zoophilic dermatophyte species causing infections in animals and humans worldwide. However, molecular epidemiological studies on this dermatophyte are still rare. In this study, we aimed to analyse the population structure and relationships between M. canis strains (n = 66) collected in southern Italy and those isolated from symptomatic and asymptomatic animals (cats, dogs and rabbits) and humans. For subtyping purposes, using multilocus sequence typing (MLST) and multilocus microsatellite typing (MLMT), we first used a limited set of strains to screen for variability. No intraspecies variability was detected in six out of the eight reference genes tested and only the ITS and IGS regions showed two and three sequence genotypes, respectively, resulting in five MLST genotypes. All of eight genes were, however, useful for discrimination among M. canis, M. audouinii and M. ferrugineum. In total, eighteen microsatellite genotypes (A-R) were recognized using MLMT based on six loci, allowing a subdivision of strains into two clusters based on the Bayesian iterative algorithm. Six MLMT genotypes were from multiple host species, while 12 genotypes were found only in one host. There were no statistically significant differences between clusters in terms of host spectrum and the presence or absence of lesions. Our results confirmed that the MLST approach is not useful for detailed subtyping and examining the population structure of M. canis, while microsatellite analysis is a powerful tool for conducting surveillance studies and gaining insight into the epidemiology of infections due to this pathogen.

Trichophyton rubrum DNA Strains in Patients with Onychomycosis with Persistent Mixed Infections Involving a Nondermatophyte Mold

BACKGROUND

Onychomycosis is estimated to occur in approximately 10% of the global population, with most cases caused by Trichophyton rubrum. Some persistent onychomycosis is caused by mixed infections of T rubrum and one or more co-infecting nondermatophyte molds (NDMs). In onychomycosis, T rubrum strain types may naturally switch and may also be triggered to switch in response to antifungal therapy. T rubrum strain types in mixed infections of onychomycosis have not been characterized.

METHODS

T rubrum DNA strains in mixed infections of onychomycosis containing co-infecting NDMs were compared with a baseline North American population through polymerase chain reaction amplification of ribosomal DNA tandemly repetitive subelements (TRSs) 1 and 2. The baseline DNA strain types were determined from 102 clinical isolates of T rubrum. The T rubrum DNA strain types from mixed infections were determined from 63 repeated toenail samples from 15 patients.

RESULTS

Two unique TRS-2 types among the clinical isolates contributed to four unique TRS-1 and TRS-2 strain types. Six TRS-1 and TRS-2 strain types represented 92% of the clinical isolates of T rubrum. Four TRS-1 and TRS-2 strain types accounted for 100% of the T rubrum within mixed infections.

CONCLUSIONS

Four unique North American T rubrum strains were identified. In support of a shared ancestry, the T rubrum DNA strain types found in mixed infections with NDMs were among the most abundant types. A population of T rubrum strains in mixed infections of onychomycosis has been characterized, with more than one strain detected in some nails. The presence of a co-infecting NDM in mixed infections may contribute to failed therapy by stabilizing the T rubrum strain type, possibly preventing the antifungal therapy-induced strain type switching observed with infections caused by T rubrum alone.

Molecular Markers Useful for Intraspecies Subtyping and Strain Differentiation of Dermatophytes

Dermatophytosis is a very common skin disorder and the most frequent infection encountered by practicing dermatologists. The identification, pathogenicity, biology, and epidemiology of dermatophytes, the causative agents of dermatophytosis, are of interest for both dermatologists and medical mycologists. Recent advances in molecular methods have provided new techniques for identifying dermatophytes, including intraspecies variations. Intraspecies subtyping and strain differentiation have made possible the tracking of infections, the identification of common sources of infections, recurrence or reinfection after treatment, and analysis of strain virulence and drug resistance. This review describes molecular methods of intraspecies subtyping and strain differentiation, including analyses of mitochondrial DNA and non-transcribed spacer regions of ribosomal RNA genes, random amplification of polymorphic DNA, and microsatellite markers, along with their advantages and limitations.

Tinea pedis: the etiology and global epidemiology of a common fungal infection

Tinea pedis, which is a dermatophytic infection of the feet, can involve the interdigital web spaces or the sides of the feet and may be a chronic or recurring condition. The most common etiological agents are anthropophiles, including Trichophyton rubrum sensu stricto, which is the most common, followed by Trichophyton interdigitale and Epidermophyton floccosum. There has been a change in this research arena, necessitating a re-evaluation of our knowledge on the topic from a multidisciplinary perspective. Thus, this review aimed to provide a solid overview of the current status and changing patterns of tinea pedis. The second half of the twentieth century witnessed a global increase in tinea pedis and a clonal spread of one major etiologic agent, T. rubrum. This phenomenon is likely due to increases in urbanization and the use of sports and fitness facilities, the growing prevalence of obesity and the aging population. For optimal patient care and management, the diagnosis of tinea pedis should be verified by microbiological analysis. In this review, we discuss the epidemiology, clinical forms, complications and mycological characteristics of tinea pedis and we highlight the pathogenesis, prevention and control parameters of this infection.

Development and validation of a microsatellite marker-based method for tracing infections by Microsporum canis

BACKGROUND

Microsporum canis is a dermatophyte fungus harbored by cats and dogs and is frequently transmitted to humans. Molecular tools able to discriminate fungal isolates at the strain level would prove extremely useful for confirming the route of infection, thus contributing to optimization of prophylaxis and hygienic regimens.

OBJECTIVE

To develop and validate a microsatellite marker-based method for use in tracking infections by M. canis.

METHODS

Primers were designed against sequences flanking the microsatellites individuated by a BLAST search using the nucleotide sequence information assembled by the M. canis CBS 113480 genome project. The PCR conditions were standardized and fragment analysis was performed using a genetic analyzer. The resolving power of the markers was investigated on 26 unrelated M. canis strains while the reproducibility of the technique and the stability of the markers were evaluated on a single strain subcultured in time as well as on 36 strains isolated from nine outbreak episodes.

RESULTS

Eight markers were recognized as being the most polymorphic within the set of M. canis strains isolated from unrelated distant hosts, with a total of 22 multilocus genotypes, which corresponded to a genotypic diversity of 97%. Repeated tests on subcultures of M. canis reference strain CBS 113480 always yielded the same results. Identical multilocus genotypes were obtained for all the isolates from each outbreak episode.

CONCLUSION

The high resolving power and reproducibility of the markers that were identified support the potential of these tools to detect sources and routes of infection by M. canis.

Griseofulvin Only Modestly Diminishes Persistence of Trichophyton tonsurans on the Scalp of Carriers

OBJECTIVES

Using genetic strain typing, we previously identified a high rate of T. tonsurans carriage among preschool-aged children attending an urban daycare center. No treatment was provided as part of the observational study; however, children when symptomatic were treated in accordance with daycare policies. This retrospective investigation examines antifungal drug therapy received during the previous investigation and characterizes the impact of treatment on persistence of the fungus on the scalp.

METHODS

Children in whom serial typeable isolates of T. tonsurans were recovered were eligible for evaluation. Clinic charts were reviewed and dispensing records obtained from the primary pharmacies serving the daycare. Infection patterns were examined before and after treatment.

RESULTS

We identified 72 dispensing records for 53 children, all of whom received griseofulvin. Nine children could not be evaluated because treatment was coincident with their last study visit. Thus, 63 treatment events in 44 children with 331 discrete infection events remained. After a single course of griseofulvin, 22.7% of children became culture negative, 6.8% acquired another strain of T. tonsurans and, 70.5% remained persistently positive with the same strain carried prior to treatment. Among those receiving a second course of therapy, 54% remained positive and the cumulative percent of children that became culture negative increased to 36.4%. If children subsequently acquiring a different strain are considered together with those that became culture negative, cumulative strain clearance was observed in 43% of children. Neither the griseofulvin dose nor the duration of time over which children were infected prior to treatment differed between those that remained positive and those that became negative.

CONCLUSIONS

Griseofulvin eradicates dermatophyte scalp carriage in less than one-half of preschool-aged children receiving between one and four 4-week courses of the drug.

CD4+ and CD8+ T cells mediated direct cytotoxic effect against Trichophyton rubrum and Trichophyton mentagrophytes

BACKGROUND

The cellular immune system is the most dominant factor in curing acute dermatophytosis. However, the exact immune mechanisms involved in generating this defense are complex and still obscure. The aim of this study was to investigate the fungicidal mechanism of T cells in the normal population versus patients with chronic fungal infections.

METHODS

Thirty patients were included in the study: 15 patients with chronic dermatophytosis and 15 normal healthy patients with a history of acute dermatophytosis. The procedures were performed as follows. 1) Proliferation and cytotoxic activity of lymphocytes cultured with various dermatophytes homogenate such as, Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum gypseum. 2) CD4(+) and CD8(+) T cells were separated by magnetic beads before culture with fresh spores of either T. mentagrophytes or T. rubrum. 3) Routine histology and ultrastructural study were performed to illustrate the mode of activity of the T cells against the dermatophytes.

RESULTS

The study showed that both CD4 and CD8 possess cytotoxic activity against dermatophytes. However, the results demonstrated a suppression of lymphocyte proliferation response and a significant lower cytotoxic effect in chronic patients. Ultra structure and histological evaluation of the culture of hyphae with CD4(+) or CD8(+) T cells showed more prominently destructive effects in the culture of cells that had been obtained from normal population than those of patients with long-lasting fungal infections.

CONCLUSION

The study suggests a selective impairment of lymphocyte function against dermatophytes, in patients with chronic dermatophytoses.

Evaluation of a PCR melting profile method for intraspecies differentiation of Trichophyton rubrum and Trichophyton interdigitale

In order to identify the source of infections caused by dermatophytes, as well as the pathogen transmission pathway, there is a need to determine methods that allow detailed genetic differentiation of the strains within the dermatophyte genera. In this work, a PCR melting profile (PCR-MP) technique based on the ligation of adaptors and the difference in melting temperatures of DNA restriction fragments was used for the first time for intraspecies genotyping of dermatophytes. Clinical isolates and reference strains of dermatophytes isolated from skin, scalp, toenails and fingernails were used for this study. PCR-MP and random amplification of polymorphic DNA (RAPD) were used to type 11 isolates of Trichophyton rubrum, 40 isolates of Trichophyton interdigitale and 14 isolates of Microsporum canis. The results distinguished five types (containing one subtype) characteristic for T. rubrum and seven types characteristic for T. interdigitale using the PCR-MP technique. Analysis conducted using RAPD revealed five types for T. rubrum and four types for T. interdigitale isolates. No differentiation was observed for the M. canis isolates with either method. These results demonstrate that PCR-MP is a reliable method for the differentiation of T. rubrum and T. interdigitale strains and yields a discriminatory power that is at least equal to that of RAPD.