Mapping the Global Spread of T. indotineae: An Update on Antifungal Resistance, Mutations, and Strategies for Effective Management

INTRODUCTION

The global spread of Trichophyton indotineae presents a pressing challenge in dermatophytosis management. This systematic review explores the current landscape of T. indotineae infections, emphasizing resistance patterns, susceptibility testing, mutational analysis, and management strategies.

METHODS

A literature search was conducted in November 2023 using Embase, PubMed, Scopus, and Web of Science databases. Inclusion criteria covered clinical trials, observational studies, case series, or case reports with T. indotineae diagnosis through molecular methods. Reports on resistance mechanisms, antifungal susceptibility testing, and management were used for data extraction.

RESULTS AND DISCUSSION

A total of 1148 articles were identified through the systematic search process, with 45 meeting the inclusion criteria. The global spread of T. indotineae is evident, with cases reported in numerous new countries in 2023. Tentative epidemiological cut-off values (ECOFFs) suggested by several groups provide insights into the likelihood of clinical resistance. The presence of specific mutations, particularly Phe397Leu, correlate with higher minimum inhibitory concentrations (MICs), indicating potential clinical resistance. Azole resistance has also been reported and investigated in T. indotineae, and is a growing concern. Nevertheless, itraconazole continues to be an alternative therapy. Recommendations for management include oral or combination therapies and individualized approaches based on mutational analysis and susceptibility testing.

CONCLUSION

Trichophyton indotineae poses a complex clinical scenario, necessitating enhanced surveillance, improved diagnostics, and cautious antifungal use. The absence of established clinical breakpoints for dermatophytes underscores the need for further research in this challenging field.

Resistance Profile, Terbinafine Resistance Screening and MALDI-TOF MS Identification of the Emerging Pathogen Trichophyton indotineae

The emerging pathogen Trichophyton indotineae, often resistant to terbinafine (TRB), is known to cause severe dermatophytoses such as tinea corporis and tinea cruris. In order to achieve successful treatment for these infections, insight in the resistance profile of T. indotineae strains and rapid, reliable identification is necessary. In this research, a screening medium was tested on T. indotineae strains (n = 20) as an indication tool of TRB resistance. The obtained results were confirmed by antifungal susceptibility testing (AST) for TRB following the in vitro broth microdilution reference method. Additionally, AST was performed for eight other antifungal drugs: fluconazole, itraconazole, voriconazole, ketoconazole, griseofulvin, ciclopirox olamine, naftifine and amorolfine. Forty-five percent of the strains were confirmed to be resistant to terbinafine. The TRB resistant strains showed elevated minimal inhibitory concentration values for naftifine and amorolfine as well. DNA sequencing of the squalene epoxidase-encoding gene showed that TRB resistance was a consequence of missense point mutations in this gene, which led to amino acid substitutions F397L or L393F. MALDI-TOF MS was used as a quick, accurate identification tool for T. indotineae, as it can be challenging to distinguish it from closely related species such as Trichophyton mentagrophytes or Trichophyton interdigitale using morphological characteristics. While MALDI-TOF MS could reliably identify ≥ 95% of the T. indotineae strains (depending on the spectral library), it could not be used to successfully distinguish TRB susceptible from TRB resistant strains.

[Conventional and molecular diagnostics in onychomycosis-part 2 : Molecular identification of causative dermatophytes by polymerase chain reaction and sequence analysis of the internal transcribed spacer region of ribosomal DNA]

Dermatophyte identification using traditional methods such as optics-based direct fluorescence microscopy and culture is nowadays supplemented by molecular biological methods. The validity of dermatophyte DNA detection with direct uniplex-polymerase chain reaction-enzyme immunoassay (PCR-EIA) in nail samples was proven by sequence analysis of the ribosomal internal transcribed spacer (ITS) region. A total of 108 dermatophytes, isolated from patients with onychomycosis, were positive for Trichophyton rubrum (TR) and Trichophyton interdigitale (TI) in culture and/or uniplex-PCR-EIA. Conventional methods for dermatophyte identification were complemented by direct uniplex-PCR-EIA and sequence analysis of the ribosomal ITS region (18S rRNA, ITS1, 5.8S rRNA, ITS2, 28S rRNA). Of 108 patients (average age 62, median age 73), 56 showed cultural growth with 31 of them being identified as TR and 23 as TI. There was high agreement with the sequence analysis. Surprisingly, the pathogen of a single nail sample was identified as T. quinckeanum (formerly T. mentagrophytes sensu stricto), a rare zoophilic dermatophyte in Germany. A single TI strain turned out to be a misidentified T. tonsurans based on the sequence analysis. In all, 34 of the 52 specimens lacking cultural growth were detected by PCR as TR, and 18 specimens could be identified as TI. The results of dermatophyte identification of culture-negative nail samples were also in agreement with the results of sequence analysis. Molecular biological methods are well applicable, and they show high reliability for direct dermatophyte identification in nail samples without prior cultivation. Especially for nail samples without cultural growth, PCR-based dermatophyte identification was highly specific and sensitive.

Deep-seated dermatophytosis caused by Trichophyton rubrum in patient with Becker muscular dystrophy

Trichophyton rubrum is a common fungal pathogen that usually causes superficial infection limited to epidermis only, so called dermatophytosis. However in immunocompromised patients, dermatophytosis can be exceptionally more invasive with extensive lesions involving deep tissues and generating sometimes systemic course. We report the case of a 43-year-old heart transplanted man, who presented with multiple deep-seated nodules and papules in the inguinal areas and in the buttocks. Involvement of Trichophyton rubrum was confirmed by culture, DNA sequencing and histological examination that showed granulomatous inflammatory infiltrates with the presence of hyphae in the dermis. Antifungal therapy with oral terbinafine for four weeks was successful; in spite of initial remnant atrophic scars, the lesions were completely cleared after four month evolution. Deep-seated invasive dermatophytosis is rare, but should be considered with immunocompromised conditions, especially when history of previous superficial dermatophytosis is present.

Severe kerion Celsi caused by Trichophyton quinckeanum: Severe kerion Celsi due to Trichophyton quinckeanum

We report a severe case of kerion Celsi of the scalp in a previously healthy 13-year-old girl due to Trichophyton quinckeanum, an emerging dermatophyte species in Europe. The species was definitely identified by DNA sequencing and the patient was successfully treated by oral terbinafine for 6 weeks. Kerion Celsi is a severe inflammatory form of tinea capitis, which is characterised by a purulent discharge and alopecia [1]. It typically occurs in children infected with zoophilic dermatophytes, such as Trichophyton mentagrophytes, and an increasing number of cases caused by other Trichophyton species has recently been reported [2]. Herein we report a severe case of kerion Celsi of the scalp caused by the emerging species Trichophyton quinckeanum, which was successfully treated by oral antifungal.

Deep dermatophytosis caused by Trichophyton rubrum in an elderly patient with CARD9 deficiency: A case report and literature review

Deep dermatophytosis is an invasive and sometimes life-threatening fungal infection mainly reported in immunocompromised patients. However, a caspase recruitment domain-containing protein 9 (CARD9) deficiency has recently been reported to cause deep dermatophytosis. Herein, we report the first Japanese case of deep dermatophytosis associated with CARD9 deficiency. An 80-year-old Japanese man with tinea corporis presented with subcutaneous nodules on his left sole. Histopathological findings revealed marked epithelioid cell granulomas with filamentous fungal structures in the deep dermis and subcutis, and the patient was diagnosed with deep dermatophytosis. Despite antifungal therapy, the subcutaneous nodule on his left sole gradually enlarged, his left calcaneal bone was invaded, and the patient finally underwent amputation of his left leg. Genetic analysis revealed a homozygous CARD9 c.586 A > G (p. Lys196Glu) variant, suggesting a CARD9 deficiency. Here, we discuss the clinical features of CARD9 deficiency-associated deep dermatophytosis with a case report and review of the literature.

Development of an agar-based screening method for terbinafine, itraconazole, and amorolfine susceptibility testing of Trichophyton spp

Resistance in dermatophytes is an emerging global public health issue. We, therefore, developed an agar-based method for screening Trichophyton spp. susceptibility to terbinafine (TRB), itraconazole (ITC), and amorolfine (AMF) and validated it using molecularly characterized isolates. Α total of 40 Trichophyton spp. isolates, 28 TRB wild type (WT) (13 T. rubrum, 10 T. mentagrophytes, 5 T. interdigitale) and 12 TRB non-WT (7 T. rubrum, 5 T. indotineae) with different alterations in the squalene epoxidase (SQLE) gene, were used. The optimal test conditions (inoculum and drug concentrations, incubation time, and temperature) and stability over time were evaluated. The method was then applied for 86 WT Trichophyton spp. clinical isolates (68 T. rubrum, 7 T. interdigitale, 6 T. tonsurans, 5 T. mentagrophytes) and 4 non-WT T. indotineae. Optimal growth of drug-free controls was observed using an inoculum of 20 µL 0.5 McFarland after 5-7 days of incubation at 30°C. The optimal concentrations that prevented the growth of WT isolates were 0.016 mg/L of TRB, 1 mg/L of ITC, and 0.25 mg/L of AMF, whereas 0.125 mg/L of TRB was used for the detection of Trichophyton strong SQLE mutants (MIC ≥0.25 mg/L). The agar plates were stable up to 4 months. Inter-observer and inter-experimental agreement were 100%, and the method successfully detected TRB non-WT Trichophyton spp. strains showing 100% agreement with the reference EUCAST methodology. An agar-based method was developed for screening Trichophyton spp. in order to detect TRB non-WT weak and strong mutant isolates facilitating their detection in non-expert routine diagnostic laboratories.

[Trichophyton mentagrophytes genotype VII increasingly causes anogenital infections]

In the course of globalization, migration and global warming, we are increasingly confronted with pathogens that do not occur naturally in our latitudes or appear in a different form. We know keratinophilic dermatophytes as the cause of tinea pedis, onychomycosis and also tinea corporis and capitis. Transmission usually occurs via domestic or farm animals and via autoinoculation. In recent years dermatophytes have gained additional importance as a possible sexually transmitted disease between immunocompetent persons. For the first time, dermatophytosis was described as a sexually transmitted infection in travelers who developed pronounced pubogenital or anogenital tinea after travelling in Southeast Asia, including Thailand, mostly after intensive sexual contact. Molecular and cultural analyses have identified Trichophyton (T.) mentagrophytes ITS (internal transcribed spacer) genotype VII as the main pathogen. Although this dermatophyte genotypically belongs to the zoophilic complex, direct (sexual) and occasionally indirect human-to-human contact with infected persons is suspected to be the current route of transmission. The infection can lead to inflammatory and purulent dermatophytosis, causing a high level of suffering. In this respect, a rapid and reliable diagnosis is essential in order to be able to initiate targeted treatment. The discovery of infection pathways and the awareness of the need to take rare diseases into account in our everyday lives will increasingly accompany us over the next few years and present us with new challenges, particularly in terms of prevention and treatment.

TrCla4 promotes actin polymerization at the hyphal tip and mycelial growth in Trichophyton rubrum

IMPORTANCE

Superficial fungal infections, such as athlete's foot, affect more than 10% of the world's population and have a significant impact on quality of life. Despite the fact that treatment-resistant fungi are a concern, there are just a few antifungal drug targets accessible, as opposed to the wide range of therapeutic targets found in bacterial infections. As a result, additional alternatives are sought. In this study, we generated a PAK TrCla4 deletion strain (∆Trcla4) of Trichophyton rubrum. The ∆Trcla4 strain exhibited deficiencies in mycelial growth, hyphal morphology, and polarized actin localization at the hyphal tip. IPA-3 and FRAX486, small chemical inhibitors of mammalian PAK, were discovered to limit fungal mycelial proliferation. According to our findings, fungal PAKs are interesting therapeutic targets for the development of new antifungal medicines.

PCR-based methods in detection and identification of dermatophytes in dogs and cats with suspected dermatophytosis in 2021 in Poland

Dermatophytes from Microsporum, Trichophyton and Epidermophyton genera are divided into geophilic, zoophilic and anthropophilic species which cause skin infection in humans and wide group of animals, mainly mammals. Main species causing dermatophytosis in dogs and cats are Microsporum and Trichophyton. Conventional mycological diagnostic technique includes Saburaud Dextrose Agar (SAD) and others medium cultures, 10% KOH mount and direct microscopy of hairs and scraping. Molecular diagnostic become more frequent in veterinary practice due to shortening of waiting time. In this study we based on two PCR methods. The nested PCR amplified CHS1 gene for dermatophytes detection, and multiplex PCR coding ITS1 and ITS2 fragments for species identification of detected derpatophytes. Most frequently detected species was Microsporum canis, mainly in young cats. Geophilic Microsporum gypseum and anthropophilic Trichophyton rubrum was found primarily in dogs. Molecular methods in dermatophytosis identification are rapid in contrast to routinely, long lasting culture.

Genomic Analysis of Antifungal Drug Resistance Induced in Trichophyton rubrum After Prolonged Culture with Terbinafine

In this study, we induced terbinafine (TRF) resistance in a T. rubrum strain in vitro for 18 months then compared the genomes of the TRF-resistant (N42-3) and TRF-susceptible wild-type (N42WT) strains to identify mutations. In the SQLE gene, N42WT had no mutation while N42-3 had a F397L mutation. We sequenced approximately 22.53 Mb of the genomes of the N43WT and N42-3 strains. Other than the F397L mutation in SQLE, there were three other genetic mutations in three different genes that were found in N42-3, but not in N43WT; however, these three mutations were not detected in other TRF-resistant T. rubrum strains. From this genome sequencing analysis, the only variation that was confirmed to be associated with drug resistance in the genome of the TRF-resistant T. rubrum was a hotspot mutation in SQLE.

Long Amplification PCR (LA-PCR) Detection of Azole Resistant Trichophyton indotineae

Trichphyton indotineae, a species newly designated in 2020 independent of T. interdigitale, comprises highly terbinafine (TRF)-resistant dermatophytosis that is epidemic in North India and spreding to worldwide. Some clinical isolates of T. indotineae have been resistance both TRF and azoles that might be caused the treatment failure. To detect the azole resistance strains, we developed a long amplification PCR (LA-PCR) detection method for the tandem repeat of the CYP51B (encoding sterol 14a-demethylase gene) in T. indotineae. Contrasting the drug susceptibility test results with the LA-PCR results confirmed a trend toward low susceptibility to azole antifungal agents in strains with amplifications of 9.5 kbp or greater (3 or more copies of CYP51B). Our results suggest that the method could be detected rapidly of low-susceptibility strains to azole antifungal agents.

Erythroderma combined with deeper dermal dermatophytosis due to Trichophyton rubrum in a patient with myasthenia gravis: first case report and literature review

BACKGROUND

Dermatophytes are the most common causative pathogens of mycoses worldwide and usually cause superficial infections. However, they can enter deep into the dermis lead to invasive dermatophytosis such as deeper dermal dermatophytosis on rare occasions. Erythroderma is a severe dermatological manifestation of various diseases resulting in generalized skin redness, but erythroderma due to fungi infections is barely reported. In this article, we reported the first case of erythroderma combined with deeper dermal dermatophytosis due to Trichophyton rubrum (T. rubrum) in a patient with myasthenia gravis.

CASE PRESENTATION

A 48-year-old man was hospitalized because of erythema with scaling and nodules covering his body for a month. The patient had a history of myasthenia gravis controlled by regularly taking prednisolone for > 10 years and accompanied by onychomycosis and tinea pedis lasting > 8 years. Based on histopathological examinations, fungal cultures, and DNA sequencing results, the patient was finally diagnosed with dermatophyte-induced erythroderma combined with deeper dermal dermatophytosis caused by T. rubrum. After 2 weeks of antifungal treatment, the patient had recovered well.

CONCLUSIONS

This case report shows that immunosuppressed patients with long histories of superficial mycoses tend to have a higher risk of developing invasive dermatophytic infections or disseminated fungal infections. Dermatologists should be alert to this condition and promptly treat the superficial dermatophytosis.

Antifungal Resistance, Susceptibility Testing and Treatment of Recalcitrant Dermatophytosis Caused by Trichophyton indotineae: A North American Perspective on Management

There is an ongoing epidemic of chronic, relapsing dermatophytoses caused by Trichophyton indotineae that are unresponsive to one or multiple antifungal agents. Although this new species may have originated from the Indian subcontinent, there has been a notable increase of its reporting in other countries. Based on current literature, antifungal susceptibility testing (AFST) showed a large variation of terbinafine minimum inhibitory concentrations (MICs) (0.04 to ≥ 32 µg/ml). Elevated terbinafine MICs can be attributed to mutations in the squalene epoxidase gene (single mutations: Leu393Phe, Leu393Ser, Phe397Leu, and double mutations: Leu393Phe/Ala448Thr, Phe397Leu/Ala448Thr). Itraconazole MICs had a lower range when compared with that of terbinafine (0.008-16 µg/ml, with most MICs falling between 0.008 µg/ml and < 1 µg/ml). The interpretation of AFST results remains challenging due to protocol variations and a lack of established breakpoints. Adoption of molecular methods for resistance detection, coupled with AFST, may provide a better evaluation of the in vitro resistance status of T. indotineae. There is limited information on treatment options for patients with confirmed T. indotineae infections by molecular diagnosis; preliminary evidence generated from case reports and case series points to itraconazole as an effective treatment modality, while terbinafine and griseofulvin are generally not effective. For physicians working outside of endemic regions, there is currently an unmet need for standardized clinical trials to establish treatment guidelines; in particular, combination therapy of oral and topical agents (e.g., itraconazole and ciclopirox), as well as with other azoles (i.e., fluconazole, voriconazole, ketoconazole), warrants further investigation as multidrug resistance is a possibility for T. indotineae.

Trichophyton mentagrophytes Internal Transcribed Spacer Genotype VIII

This case report describes large, annular, scaly, and erythematous plaques in the axillae and legs extending from the groin as well as involvement of the chest surrounding the areola.

Reliable and rapid identification of terbinafine resistance in dermatophytic nail and skin infections

BACKGROUND

Fungal infections are the most frequent dermatoses. The gold standard treatment for dermatophytosis is the squalene epoxidase (SQLE) inhibitor terbinafine. Pathogenic dermatophytes resistant to terbinafine are an emerging global threat. Here, we determine the proportion of resistant fungal skin infections, analyse the molecular mechanisms of terbinafine resistance, and validate a method for its reliable rapid identification.

METHODS

Between 2013 and 2021, we screened 5634 consecutively isolated Trichophyton for antifungal resistance determined by hyphal growth on Sabouraud dextrose agar medium containing 0.2 μg/mL terbinafine. All Trichophyton isolates with preserved growth capacity in the presence of terbinafine underwent SQLE sequencing. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method.

RESULTS

Over an 8-year period, the proportion of fungal skin infections resistant to terbinafine increased from 0.63% in 2013 to 1.3% in 2021. Our routine phenotypic in vitro screening analysis identified 0.83% (n = 47/5634) of Trichophyton strains with in vitro terbinafine resistance. Molecular screening detected a mutation in the SQLE in all cases. Mutations L393F, L393S, F397L, F397I, F397V, Q408K, F415I, F415S, F415V, H440Y, or A398 A399 G400 deletion were detected in Trichophyton rubrum. Mutations L393F and F397L were the most frequent. In contrast, all mutations detected in T. mentagrophytes/T. interdigitale complex strains were F397L, except for one strain with L393S. All 47 strains featured significantly higher MICs than terbinafine-sensitive controls. The mutation-related range of MICs varied between 0.004 and 16.0 μg/mL, with MIC as low as 0.015 μg/mL conferring clinical resistance to standard terbinafine dosing.

CONCLUSIONS

Based on our data, we propose MIC of 0.015 μg/mL as a minimum breakpoint for predicting clinically relevant terbinafine treatment failure to standard oral dosing for dermatophyte infections. We further propose growth on Sabouraud dextrose agar medium containing 0.2 μg/mL terbinafine and SQLE sequencing as fungal sporulation-independent methods for rapid and reliable detection of terbinafine resistance.

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.

Clinical evaluation of a dermatophyte RT-PCR assay and its impact on the turn-around-time: A prospective study

Onychomycosis is an important public health problem whose prevalence continues to grow and impact public health at several levels. Nevertheless, today the main diagnostic methods used in routine practice have many drawbacks. The aim of this study was to evaluate, for the first time, the clinical performance of a new multiplex polymerase chain reaction (PCR) (Novaplex®) in the identification of the causative agent on nail samples, and its impact on the turnaround time, compared to our traditional laboratory methods. From June 2022 to December 2022, all nail samples sent to our laboratory for suspected onychomycosis were included in this prospective study. We collected for each sample the results obtained with the Novaplex® PCR method and with the traditional direct microscopy examination and culture. Each discordant result was checked using a third method, which is another PCR method (DermaGenius® kit) as a resolver. For culture-positive samples, a turnaround time was calculated and compared to the one obtained with the Novaplex® method. A total of 131 samples were included. Among them, 5 were positive (3.8%) on direct microscopy, 33 were positive (25.2%) after culture, and 98 were negative (74.8%). All positive (n = 33) and negative (n = 69) cultures were also positive/negative with the Novaplex® PCR. Twenty-nine samples were positive with the Novaplex® method but negative with culture (discordant results). The percentage agreement between the culture and the Novaplex® methods was 77.9% (102 out of 131). While tested with the resolver (DermaGenius® PCR), 28 out of 29 discordant results were similarly found positive. The percentage agreement between the two PCR methods (Novaplex® and DermaGenius®) was 96.6%. The Novaplex® PCR method evaluated proved to be very reliable and allowed the direct identification of 62 out of 131 positive samples (47.3%) with the following distribution: 79.0% of Trichophyton rubrum complex, 11.3% of Trichophyton mentagrophytes complex, 6.5% of both Trichophyton rubrum complex and Trichophyton mentagrophytes complex, and 3.2% of Candida albicans. The median time [± 95% CI] for positive culture (between incubation and validation of the final identification) was 15 [12-23] days, while the turnaround time for the Novaplex® method adapted to our clinical laboratory routine is ≤7 days. Laboratory confirmation of onychomycosis is crucial and should always be obtained before starting treatment. The evaluated PCR method offered a rapid, reliable, robust, and inexpensive method of identification of the causative agent compared to traditional methods.

The Domestic Isolation of Terbinafine- and Itraconazole-Resistant Trichophyton indotineae in Chinese Mainland

BACKGROUND

Trichophyton indotineae, a new species of dermatophytes, has become a significant concern in treating dermatophytosis due to the high level of terbinafine resistance reported in India and even worldwide.

OBJECTIVES

This study aimed to report the terbinafine- and itraconazole-resistant T. indotineae in Chinese mainland, by identifying the phylogenetic classification of the isolate strain, and detecting the drug resistance, gene mutation and expression.

PATIENTS/METHODS

The skin scales of the patient were cultured on SDA and the isolate was authenticated by DNA sequencing and MALDI-TOF MS. Antifungal susceptibility testing was performed following the M38-A2 CLSI protocol to examine the MICs values of terbinafine, itraconazole, fluconazole, etc. The strain was screened for mutations in the squalene epoxidase (SQLE) gene by Sanger sequencing and detected the expression of CYP51A and CYP51B by qRT-PCR.

RESULTS

A multi-resistant ITS genotype VIII sibling of the T. mentagrophytes complex (T. indotineae) was isolated in Chinese mainland. The strain harbored high terbinafine MIC of > 32 μg/mL and itraconazole MIC of 1.0 μg/mL, which was identified a mutation in the squalene epoxidase gene with amino acid substitution (Phe397Leu, mutation 1191C > A). In addition, overexpression of CYP51A and CYP51B was observed. With multiple relapses, the patient finally achieved clinical cure by itraconazole pulse therapy and topical clotrimazole cream for 5 weeks.

CONCLUSIONS

The first domestic strain of terbinafine- and itraconazole-resistant T. indotineae from a patient in Chinese mainland was isolated. Itraconazole pulse therapy can be an effective method for the treatment of T. indotineae.

An update on the myriad antifungal resistance mechanisms in dermatophytes and the place of experimental and existential therapeutic agents for Trichophyton complex implicated in tinea corporis and cruris

INTRODUCTION

There is an epidemic emergence of increased resistance in dermatophytes with to antifungal drugs with ergosterol1 (Erg1) and Erg11 mutations to terbinafine and azoles. Apart from mutations, mechanisms that predict clinical failure include efflux pumps, cellular kinases, heat shock proteins (Hsp), and biofilms. Apart from itraconazole and SUBATM (Super-Bioavailable) itraconazole, measures that can be used in terbinafine failure include efflux-pump inhibitors, Hsp inhibitors and judicious use of antifungal drugs (topical + systemic) combinations.

AREAS COVERED

A PubMed search was done for the relevant studies and reviews published in the last 22 years using keywords dermatophytes OR Trichophyton, anti-fungal, resistance, mechanism and fungal AND resistance mechanisms. Our aim was to look for literature on prevalent species and we specifically researched studies on Trichophyton genus. We have analyzed varied antifungal drug mechanisms and detailed varied experimental and approved drugs to treat recalcitrant dermatophytosis.

EXPERT OPINION

Apart from administering drugs with low minimum inhibitory concentration, combinations of oral and topical antifungals (based on synergy data) and new formulations of existing drugs are useful in recalcitrant cases. There is a need for research into resistance mechanism of the existent Trichophyton strains in therapeutic failures in tinea corporis & cruris instead of data derived from laboratory strains which may not mirror clinical failures.

Sexually Transmitted Trichophyton mentagrophytes Genotype VII Infection among Men Who Have Sex with Men

Transmission of dermatophytes, especially Trichophyton mentagrophytes genotype VII, during sexual intercourse has been recently reported. We report 13 such cases in France. All patients were male; 12 were men who have sex with men. Our findings suggest sexual transmission of this pathogen within a specific population, men who have sex with men.

Review on host-pathogen interaction in dermatophyte infections

Dermatophytosis is a common superficial fungal infection of the skin and its appendages caused by dermatophytes. Recent times have witnessed a dynamic evolution of dermatophytes driven by their ecology, reproduction, pathogenicity and host immune response, influenced by population migration and socioeconomic status. Dermatophytes establish infection following successful adherence of arthroconidia to the surface of keratinized tissues. The proteolytic enzymes released during adherence and invasion not only ascertain their survival but also allow the persistence of infection in the host. While the cutaneous immune surveillance mechanism, after antigen exposure and presentation, leads to activation of T lymphocytes and subsequent clonal expansion generating effector T cells that differentially polarize to a predominant Th17 response, the response fails to eliminate the pathogen despite the presence of high levels of IFN-γ. In chronic dermatophytosis, antigens are a constant source of stimulus promoting a dysregulated Th17 response causing inflammation. The host-derived iTreg response fails to counterbalance the inflammation and instead polarizes to Th17 lineage, aggravating the chronicity of the infection. Increasing antifungal resistance and recalcitrant dermatophytosis has impeded the overall clinical remission. Human genetic research has the potential to generate knowledge to explore new therapeutic targets. The review focuses on understanding specific virulence factors involved in pathogenesis and defining the role of dysregulated host immune response against chronic dermatophytic infections for future management strategies.

Dual RNA-Sequencing and Liquid Chromatography-Mass Spectrometry Unveil Specific Insights on the Pathogenicity of Trichophyton mentagrophytes Complex

Trichophyton mentagrophytes is increasingly considered to be a public health hazard because it causes the most severe manifestations of dermatophytosis. In this study, we performed a series of studies to determine the pathogenicity of the T. mentagrophytes complex. We show that the T. mentagrophytes complex interacts with keratinocytes through pattern-recognition receptors‒MAPK/noncanonical NF-κB pathways and that the hyphal form of T. mentagrophytes is responsible for the increased inflammatory responses in keratinocytes. Moreover, SN-38 is likely a toxin of T. mentagrophytes that induces apoptosis in keratinocytes both in vivo and in vitro. Our results explain the severe pathogenicity and destructiveness of T. mentagrophytes observed in the clinic and pave the way for designing novel toxin-directed therapies to improve patient outcomes.

Metabolic phenotype analysis of Trichophyton rubrum after laser irradiation

BACKGROUND

Biological phenotypes are important characteristics of microorganisms, and often reflect their genotype and genotype changes. Traditionally, Trichophyton rubrum (T. rubrum) phenotypes were detected using carbon source assimilation tests, during which the types of tested substances are limited. In addition, the operation is complicated, and only one substance can be tested at once. To observe the changes of the metabolic phenotype of T. rubrum after laser irradiation, a high-throughput phenotype microarray system was used to analyze the metabolism of different carbon, nitrogen, phosphorus and sulfur source substrates in a Biolog metabolic phenotyping system.

RESULTS

The strain of T. rubrum used in this study can effectively utilize 33 carbon, 20 nitrogen, 16 phosphorus, and 13 sulfur source substrates prior to laser irradiation. After laser irradiation, the strain was able to utilize 10 carbon, 12 nitrogen, 12 phosphorus, and 8 sulfur source substrates. The degree of utilization was significantly decreased compared with the control. Both groups efficiently utilized saccharides and organic acids as carbon sources as well as some amino acids as nitrogen sources for growth. The number of substrates utilized by T. rubrum after laser irradiation were significantly reduced, especially carbon substrates. Some substrates utilization degree in the laser treated group was higher than control, such as D-glucosamine, L-glutamine, D-2-Phospho-Glyceric Acid, D-glucosamine-6-phosphate, and D-methionine.

CONCLUSION

Laser irradiation of T. rubrum may lead to changes in the metabolic substrate and metabolic pathway, thus weakening the activity of the strain.

European Hedgehogs (Erinaceus europaeus L.) as a Reservoir of Dermatophytes in Poland

The European hedgehog (Erinaceus europaeus Linnaeus) frequently colonises areas located close to human life in cities, as these are more suitable nest sites offering an abundance of food and allowing avoidance of predators. However, urbanisation has a significant impact on the epidemiology of infectious diseases, including dermatophytoses, the primary source of which are wild animals. In this study, we determined the spectrum of dermatophytes isolated from the European hedgehog and assessed their susceptibility profile to antifungal drugs. Symptomatic and asymptomatic dermatophyte infections were observed in 7.7% and 8% of the 182 examined free-living hedgehogs, respectively. In the pool of the isolated dermatophyte strains, Trichophyton erinacei was dominant (29.9%), followed by Trichophyton mentagrophytes (17.9%), Trichophyton benhamiae (13.4%), Nannizzia gypsea (11.9%), Microsporum canis (10.4%), Nannizzia nana (7.5%), Paraphyton cookei (6.0%), and Nannizzia fulva (3.0%). Susceptibility tests revealed the highest activity of luliconazole and the lowest of activity fluconazole among the azole drugs applied. Although terbinafine generally exhibited high efficacy, two Trichophyton mentagrophytes isolates showed resistance to this drug (MIC = 2 µg/ml) resulting from missense mutations in the SQLE gene corresponding to the amino acid substitution Leu393Phe. Summarising, our study has also revealed that such wildlife animals as hedgehogs can be a reservoir of pathogenic human dermatophytes, including harmful strains resistant to commonly used antifungal drugs.

Extensive Dermatophytosis Caused by Terbinafine-Resistant Trichophyton indotineae, France

Extensive dermatophytosis caused by terbinafine-resistant Trichophyton indotineae harboring Phe397Leu and Leu393Ser substitutions in the squalene epoxidase enzyme was diagnosed in France. Analysis of internal transcribed spacer sequences revealed the wide spread of this species in Asia and Europe. Detection of T. indotineae in animals suggests their possible role as reservoirs.

Emergence of Difficult-to-Treat Tinea Corporis Caused by Trichophyton mentagrophytes Complex Isolates, Paris, France

We describe 7 cases of extensive tinea corporis since 2018 in a hospital in Paris, France, after failure to cure with terbinafine. Molecular analysis indicated Trichophyton mentagrophytes internal transcribed spacer type VIII (T. indotineae). This strain, which has mutations in the squalene epoxidase gene, is spreading on the Indian subcontinent.

Molecular identification and antifungal susceptibility of 75 clinical isolates of Trichophyton spp. from southern Brazil

BACKGROUND

Dermatophytoses affect more than 20% of the world's population and is caused by filamentous fungi, mainly of the genus Trichophyton. The species identification through microscopic direct examination and culture methods is challenging, with molecular presenting high sensitivity and specificity. Although there are several therapy options for dermatophyte infections, treatment failures and antifungal resistance are growing concerns.

OBJECTIVE

This study aimed to identify clinical isolates of Trichophyton spp. from southern Brazil using molecular methods and determine their in-vitro antifungal susceptibility.

MATERIAL AND METHODS

Seventy-five isolates were identified through sequencing of the ITS region. The exposure to seven antifungals drugs was performed according to protocol M28-A2 of the Clinical and Laboratory Standards Institute (CLSI).

RESULTS

Sixty-one isolates (81%) were identified as T. interdigitale, which differs from the epidemiological data present in the literature. Thirteen isolates were identified as T. rubrum and one as T. tonsurans. Terbinafine was the most effective antifungal, followed by itraconazole and voriconazole, which is in accordance with the results reported in previous studies.

CONCLUSIONS

The use of molecular methods to identify Trichophyton spp. clinical isolates and the performance of susceptibility tests are relevant to epidemiological data, identification of the emergence of antifungal resistance, and to help to translate the in-vitro antifungal susceptibility results into clinical practice.

Taxonomy of the Trichophyton mentagrophytes/T. interdigitale Species Complex Harboring the Highly Virulent, Multiresistant Genotype T. indotineae

A severe outbreak of highly virulent and multi-resistant dermatophytosis by species in the Trichophyton mentagrophytes/T. interdigitale complex is ongoing in India. The correct identity of the etiologic agent is a much-debated issue. In order to define species limits, a taxonomic study was undertaken combining molecular, morphological, and physiological characteristics as evidence of classification. Molecular characteristics show that T. mentagrophytes s. str. and T. interdigitale s. str. can be distinguished with difficulty from each other, but are unambiguously different from the Indian genotype, T. indotineae by sequences of the HMG gene. The entities were confirmed by multilocus analysis using tanglegrams. Phenotypic characters of morphology and physiology are not diagnostic, but statistically significant differences are observed between the molecular siblings. These properties may be drivers of separate evolutionary trends. Trichophyton mentagrophytes represents the ancestral, homothallic cloud of genotypes with a probable geophilic lifestyle, while T. indotineae and T. interdigitale behave as anthropophilic, clonal offshoots. The origin of T. indotineae, which currently causes a significant public health problem, is zoonotic, and its emergence is likely due to widespread misuse of antifungals.

Assessment of the mechanism of drug resistance in Trichophyton mentagrophytes in response to various substances

BACKGROUND

Trichophyton mentagrophyte (TM), a zoonotic pathogen, has been endangering public health due to emerging drug resistance. Although increased attention is paid to this issue, there is very limited research available on drug resistance in TM. In this study, we studied the gene and proteomic changes, morphological changes, cellular fat localization, fat content changes, and biofilm of TM treated with different substances.

RESULTS

The TM growth curve showed a positive correlation with the concentration of Fenarimol (FE), genistein (GE), clotrimazole (KM), and Miconazole nitrate salt (MK). The morphology of TM cells changed in different degrees after treatment with different substances as observed by TEM and SEM. The results showed that under KM and berberine hydrochloride (BB) treatment, a total of 3305 differentially expressed genes were detected, with the highest number in the KM-treated group (578 up-regulated and 615 down-regulated). A total of 847 proteins and 1850 peptides were identified in TM proteomics. Nile red staining showed that the fat content of TM was significantly higher in the BB-, ethidium bromide- (EB), FE-, KM-, Adriamycin hydrochloride- (YA), and MK-treated group compared to the control group. Results of the biofilm thickness showed that it gradually increased under treatment with specific concentrations of KM or BB, which may be related to the up-regulation of ERG25 and CYP related gene proteins.

CONCLUSIONS

It is suggested that in order to effectively deal with dermatomycosis caused by TM, it is necessary to inhibit the expression of ERG25 and CYP related genes and fat metabolism, which can result in the inhibition of the production of biofilm by the fungus and solve the problem of fungal drug resistance in clinical settings.

Molecular and Phenotypic Characterization of Nannizzia (Arthrodermataceae)

Phylogenetic studies of the family Arthrodermataceae have revealed seven monophyletic dermatophyte clades representing the genera Trichophyton, Epidermophyton, Nannizzia, Lophophyton, Paraphyton, Microsporum, and Arthroderma. Members of the genus Nannizzia are geo- or zoophiles that occasionally infect humans. With the newly proposed taxonomy, the genus Nannizzia comprises thirteen species, i.e., Nannizzia aenigmatica, N. corniculata, N. duboisii, N. fulva, N. graeserae, N. gypsea, N. nana, N. incurvata, N. perplicata, N. persicolor, N. praecox, and two novel species. Nannizzia polymorpha sp. nov. was isolated from a skin lesion of a patient from French Guiana. For the strain originally described as Microsporum racemosum by Borelli in 1965, we proposed Nannizzia lorica nom. nov. The species are fully characterized with five sequenced loci (ITS, LSU, TUB2, RP 60S L1 and TEF3), combined with morphology of the asexual form and physiological features. A key to the species based on phenotypic and physiological characters is provided.

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.

Genes coding for LysM domains in the dermatophyte Trichophyton rubrum: A transcription analysis

The filamentous fungus Trichophyton rubrum is a pathogen that causes superficial mycoses in humans, predominantly in keratinized tissues. The occurrence of dermatophytoses has increased in the last decades, mainly in immunocompromised patients, warranting research on the mechanisms involved in dermatophyte virulence. The genomes of dermatophytes are known to be enriched in genes coding for proteins containing the LysM domain, a carbohydrate-binding module, indicating the possible involvement of these genes in virulence. Although the LysM domains have already been described in other fungi, their biological functions in dermatophytes are unknown. Here we assessed the transcription of genes encoding proteins containing the LysM domains in T. rubrum grown on different substrates using quantitative real-time polymerase chain reaction. Some of these genes showed changes in transcription levels when T. rubrum was grown on keratin. In silico analyses suggest that some of these proteins share features, namely, they are anchored in the plasma membrane and contain the catalytic domain chitinase II and signal peptide domains. Here we show a detailed study of genes encoding the proteins with LysM-containing domains in T. rubrum, aiming to contribute to the understanding of their functions in dermatophytes.

Rapid detection of terbinafine resistance in Trichophyton species by Amplified refractory mutation system-polymerase chain reaction

Dermatophytosis has gained interest in India due to rise in terbinafine resistance and difficulty in management of recalcitrant disease. The terbinafine resistance in dermatophytes is attributed to single nucleotide polymorphisms (SNPs) in squalene epoxidase (SE) gene. We evaluated the utility of amplified refractory mutation system polymerase chain reaction (ARMS PCR) for detection of previously reported point mutations, including a mutation C1191A in the SE gene in Trichophyton species. ARMS PCR was standardized using nine non-wild type isolates and two wild type isolates of Trichophyton species. Study included 214 patients with dermatophyte infection from March through December 2017. Antifungal susceptibility testing of isolated dermatophytes was performed according to CLSI-M38A2 guidelines. Among dermatophytes isolated in 68.2% (146/214) patients, Trichophyton species were predominant (66.4%). High (>2 mg/L, cut off) minimum inhibitory concentrations to terbinafine were noted in 15 (15.4%) Trichophyton mentagrophytes complex isolates. A complete agreement was noted between ARMS PCR assay and DNA sequencing. C to A transversion was responsible for amino acid substitution in 397th position of SE gene in terbinafine resistant isolates. Thus, the ARMS PCR assay is a simple and reliable method to detect terbinafine-resistant Trichophyton isolates.

Auxotrophic mutations of Trichophyton rubrum created by in vitro synthesized Cas9 ribonucleoprotein

BACKGROUND

Trichophyton rubrum is an obligate human parasitic fungus and responsible for approximately 80-90% of dermatomycosis in human. Molecular genetic manipulations of this pathogen are challenging and available tools and protocols are only rudimentary. We adapt molecular genetics methods of well established fungal model organism, to knock out genes in T. rubrum. For the adaptation, crucial modifications are necessary. With the implementation of in vitro synthesized Cas9-sgRNA ribonucleoprotein complex, it is possible to adapt molecular genetic methods, to knock out genes in T. rubrum.

RESULTS

The gene knock-out method is based on integration of a selection marker into the target site, to interrupt the gene translation. The target gene gets preassigned by the homologous sequence of the in vitro synthesized Cas9-sgRNA ribonucleoprotein complex. To develop the method, we first isolated and characterized a T. rubrum strain with a high amount of microconidia. Next, we developed a transformation protocol, whereby the Cas9-sgRNA ribonucleoprotein gets delivered into the fungal protoplast by the PEG method. We knocked out the URA3 gene and resulted, as predicted, uracil auxotrophic strains. These strains can be used for specific gene knock-outs by reintegrating the URA3 fragment and selection on uracil lacking cultivation media. Exemplary, we knocked out the TRP3 gene and got the predicted phenotype, tryptophan auxotrophic strains. The mutation had been verified by sequencing.

CONCLUSIONS

We developed a method, based on in vitro synthesized Cas9-sgRNA ribonucleoprotein complex, for target specific gene knock-outs in T. rubrum. We knocked out the Ura3 gene and resulted uracil auxotrophic strains. These strains were used for target specific gene knock-outs by reintegrating the Ura3 fragment into the target gene site to interrupt the gene transcription. The developed method allows to adapt sophisticate gene manipulation methods of model fungal species to non-model species.

Whole-genome resequencing of Trichophyton rubrum provides insights into population differentiation and drug resistance

Trichophyton rubrum (T. rubrum) is anthropophilic fungus and thus a very common cause of dermatophyte infections around the world. Infection of T. rubrum could result in conditions such as tinea capitis, tinea corporis, tinea inguinalis, tinea manus, tinea unguium, or tinea pedis. Because of this, the resistance of T. rubrum to antifungal therapies has drawn extensive research interest. However, the pathogenic characteristics of T. rubrum, such as site of infections, geographic location and host groups, have yet to be explored. In this study, the whole genome of 48 strains from different regions is resequenced and the population structure and association of single nucleotide polymorphism with resistance to six widely used antifungal drugs are analyzed. A total of 23,394 genomic variations are detected, which cover 2165 genes with only 15.14% of the variations located in exons. The population structure of T. rubrum is monomorphic, and genetic diversity is very low. Population structure analysis shows that the 48 sampled strains can be divided into two sub-populations. The gene TERG_08771 harboring the highest SNPs density is found to be associated with resistance to voriconazole. Although many proteins have yet to be identified and explored, association studies could still be useful to identify drug resistance or drug-susceptible loci, which would warrant further insightful investigations.

Terbinafine resistance conferred by multiple copies of the salicylate 1-monooxygenase gene in Trichophyton rubrum

Resistance to antifungals is a leading concern in the treatment of human mycoses. We demonstrate that the salA gene, encoding salicylate 1-monooxygenase, is involved in resistance of the dermatophyte Trichophyton rubrum to terbinafine, one of the most effective antifungal drugs against dermatophytes. A strain with multiple copies of salA was constructed and exhibited elevated expression of salA and increased terbinafine resistance. This reflects a mechanism not yet reported in a pathogenic fungus.

[Tinea barbae profunda due to Trichophyton mentagrophytes : Case report and review]

Tinea barbae is a rare dermatomycocis, by definition follicular bound in the beard area of adult men. Manifestation usually starts with erythema accompanied by desquamation. Deeper distribution along terminal hairs leads to folliculitis with formation of pustules and nodes as well as abscesses; fixed adherent yellowish crusts may appear. Frequently there is locoregional swelling of the lymph nodes and occasionally a deterioration of general condition with (sub)febrile temperatures. Often this leads to the initial suspected diagnosis of a bacterial folliculitis barbae or impetigo contagiosa. Tinea barbae is mostly induced by species of the genus Trichophyton (T.). The pathogens are diverse and are mostly zoophilic, sometimes anthropophilic and rarely geophilic dermatophytes. With the help of a specific anamnesis and diagnostic procedure, including mycological examinations, histology and molecular detection of dermatophytes via polymerase chain reaction (PCR), tinea barbae-in our patient induced by T. mentagrophytes-can be rapidly diagnosed. Early initiation and adequate treatment duration lead to restitutio ad integrum.

Extensive tinea capitis and corporis in a child caused by Trichophyton verrucosum

A 3-year-old boy presented with multiple lesions of tinea corporis with dermatophytids, and subsequent inflammatory lesions with alopecia on the scalp. At the beginning, topical clobetasone butyrate was prescribed. The infection was diagnosed as dermatophytosis on the basis of positive direct microscopy and fungal culture. The etiological agent was isolated from all sampled sites and identified as Trichophyton verrucosum. Clonal nature of the infection was confirmed by random amplified polymorphic DNA (RAPD) analysis. The child lived in close vicinity of cattle. He was successfully treated with itraconazole.

STE20/PAKA Protein Kinase Gene Releases an Autoinhibitory Domain through Pre-mRNA Alternative Splicing in the Dermatophyte Trichophyton rubrum

Signaling pathways are highly diverse in filamentous fungi, allowing the cells to receive and process ambient information. Interaction of components from different pathways results in signaling networks. The mitogen-activated protein kinase (MAPK) pathway is dependent on phosphorylation that is accomplished by kinase proteins. Thus, the STE/PAK protein kinase family plays essential roles in MAPK signal transduction, regulating several cellular functions. The STE/PAK protein displays an autoinhibitory (Cdc42/Rac interactive binding-CRIB) domain on its N-terminal portion, which interacts with the C-terminal catalytic kinase domain. Based on current knowledge, for the STE/PAK kinase to be activated, molecular signals (e.g., interaction with the activated form of Rac1 and Cdc42 proteins) or proteolytic cleavage by caspase 3 is necessary. Both mechanisms release the kinase domain from the CRIB interaction. Here, we hypothesize a novel molecular mechanism for the activation of STE20/PAKA kinase in Trichophyton rubrum based on an alternative pre-mRNA splicing process. Our data suggest that, because of the retention of intron 1 of this gene, it is theoretically possible that the translation of STE20/PAKA kinase will be free of its autoinhibitory CRIB domain. These findings indicate a rapid response system to environmental changes. Furthermore, STE20/PAKA may be a potential T. rubrum virulence factor and an interesting target for new drugs against dermatophytes.

PRP8 intein in dermatophytes: Evolution and species identification

Dermatophytes are keratinophilic fungi belonging to the family Arthrodermataceae. Despite having a monophyletic origin, its systematics has always been complex and controversial. Sequencing of nuclear ribosomal ITS and D1/D2 rDNA has been proposed as an efficient tool for identifying species in this group of fungi, while multilocus analyses have been used for phylogenetic species recognition. However, the search for new markers, with sequence and size variation, which enable species identification in only one polymerase chain reaction (PCR) step, is very attractive. Inteins seems to fulfill these characteristics. They are self-splicing genetic elements present within housekeeping coding genes, such as PRP8, that codify the most important protein of the spliceosome. The PRP8 intein has been described for Microsporum canis in databases but has not been studied in dermatophytes in any other published work. Thus, our aim was to determine the potential of this intervening element for establishing phylogenetic relationships among dermatophytes and for identifying species. It was found that all studied species have a full-length PRP8 intein with a Homing Endonuclease belonging to the family LAGLIDADG. Phylogenetic analyses were consistent with other previous phylogenies, confirming Epidermophyton floccosum in the same clade of the Arthroderma gypseum complex, Microsporum audouinii close to M. canis, differentiating A. gypseum from Arthroderma incurvatum, and in addition, better defining the Trichophyton interdigitale and Trichophyton rubrum species grouping. Length polymorphism in the HE region enables identification of the most relevant Microsporum species by a simple PCR-electrophoresis assay. Intein PRP8 within dermatophytes is a powerful additional tool for identifying and systematizing dermatophytes.

Mutation in the Squalene Epoxidase Gene of Trichophyton interdigitale and Trichophyton rubrum Associated with Allylamine Resistance

Dermatophytosis, the commonest superficial fungal infection, has gained recent attention due to its change of epidemiology and treatment failures. Despite the availability of several agents effective against dermatophytes, the incidences of chronic infection, reinfection, and treatment failures are on the rise. Trichophyton rubrum and Trichophyton interdigitale are the two species most frequently identified among clinical isolates in India. Consecutive patients (n = 195) with suspected dermatophytosis during the second half of 2014 were included in this study. Patients were categorized into relapse and new cases according to standard definitions. Antifungal susceptibility testing of the isolated Trichophyton species (n = 127) was carried out with 12 antifungal agents: fluconazole, voriconazole, itraconazole, ketoconazole, sertaconazole, clotrimazole, terbinafine, naftifine, amorolfine, ciclopirox olamine, griseofulvin, and luliconazole. The squalene epoxidase gene was evaluated for mutation (if any) in 15 T. interdigitale and 5 T. rubrum isolates exhibiting high MICs for terbinafine. A T1189C mutation was observed in four T. interdigitale and two T. rubrum isolates. This transition leads to the change of phenylalanine to leucine in the 397th position of the squalene epoxidase enzyme. In homology modeling the mutant residue was smaller than the wild type and positioned in the dominant site of squalene epoxidase during drug interaction, which may lead to a failure to block the ergosterol biosynthesis pathway by the antifungal drug.

Whole-Genome Analysis Illustrates Global Clonal Population Structure of the Ubiquitous Dermatophyte Pathogen Trichophyton rubrum

Dermatophytes include fungal species that infect humans, as well as those that also infect other animals or only grow in the environment. The dermatophyte species Trichophyton rubrum is a frequent cause of skin infection in immunocompetent individuals. While members of the T. rubrum species complex have been further categorized based on various morphologies, their population structure and ability to undergo sexual reproduction are not well understood. In this study, we analyze a large set of T. rubrum and T. interdigitale isolates to examine mating types, evidence of mating, and genetic variation. We find that nearly all isolates of T. rubrum are of a single mating type, and that incubation with T. rubrum "morphotype" megninii isolates of the other mating type failed to induce sexual development. While the region around the mating type locus is characterized by a higher frequency of SNPs compared to other genomic regions, we find that the population is remarkably clonal, with highly conserved gene content, low levels of variation, and little evidence of recombination. These results support a model of recent transition to asexual growth when this species specialized to growth on human hosts.

Single-nucleotide polymorphism in a local population of Trichophyton rubrum

Trichophyton rubrum is an important causative agent of superficial mycoses worldwide. To uncover a genetic composition of a local population of this fungus, we sequenced A7C99_6411 and A7C99_6714 loci, coding for hypothetical proteins and revealed two complex genotypes, differing by a single missense mutation in each locus. One of the two A7C99_6411/6714 genotypes was not found in tinea pedis cases and demonstrated mostly longer TRS-1 elements when compared to another genotype. Thus, we present a description of nucleotide polymorphism in protein-coding loci in T. rubrum and provide evidence for ecological preferences of T. rubrum genotypes at a local scale.

Compensatory expression of multidrug-resistance genes encoding ABC transporters in dermatophytes

Genomic sequencing of several dermatophyte species has revealed that they show small differences in genetic content and genome organization, although each fungus has adapted to specific niches. Thus, it seemed relevant to compare gene expression between species. Here, we examined the transcription modulation of three ATP-binding cassette (ABC) transporter genes (pdr1, mdr2 and mdr4), which code for membrane transporter proteins in four species of Trichophyton ; T. interdigitale, T. rubrum, T. tonsurans and T. equinum . These fungal species were challenged with sub-lethal doses of griseofulvin, itraconazole, terbinafine and amphotericin B. A mutant strain of T. interdigitale, Δmdr2, was also analysed for the modulation of pdr1 and mdr4 genes to evaluate the possible functional interaction among these three genes. Disruption of the mdr2 gene resulted in the accumulation of high levels of mdr4 transcripts when challenged with griseofulvin, suggesting that the mdr4 gene is compensating for the inactivation of mdr2 by providing resistance to this antifungal. Although the three ABC transporter genes have high homology between the four dermatophytes analysed, it is likely that they have specific functions, suggesting that the action of each drug is dependent on other factors inherent to each species. Our data suggest that these ABC transporter genes act synergistically in dermatophytes, and they may compensate for one another when challenged with antifungal drugs. This may be an important cause of therapeutic failure when treating fungal infections.

Trichphyton violaceum and T. soudanese: re-emerging pathogens in Italy, 2005-2013

Dermatomycoses due to Trichophyton violaceum are described in Mediterranean Countries, North Africa and in the Horn of Africa where T. soudanense is present too, but it was rare until few years ago in Italy. Aim of the present study was to evaluate an Italian multicenter 9 year (2005-2013) experience concerning these re-emerging pathogens. Fifty three fungal strains were sent from clinical laboratories to the Medical Mycology Committee (CoSM)--Italian Association of Clinical Microbiology (AMCLI) for mycological confirmation. Strains were identified as T. violaceum (23) and T. soudanense (30) by phenotypic and genotypic methods. These dermatophytes present epidemiological (high rate of inter-human transmission, high risk among adopted children coming from countries of either the Horn of Africa or Sub-Saharan Africa also in outbreaks of tinea capitis) and clinical peculiarities (reduced alopecia, presence of exudative lesions) confirming the originality of these "imported" dermatophyte infections.

Generalized superficial mycosis caused by Trichophyton raubitschekii in China: case report and review of the literature

This is a generalized superficial mycosis case from which Trichophyton raubitschekii was isolated. A male adult was presented with a 3-year history of fingernail and toenail changes, and a 50-day history of severe and multiple skin lesions. He also complained of intense itching. T. raubitschekii was identified from every skin lesion (trunk, extremities and nail) through microscopic examination, physiological experiment and DNA sequencing. Generalized superficial mycosis was diagnosed and treated by administering a combination of oral (terbinafine tablets) and topical (naftifine hydrochloride and ketoconazole cream) antimycotic drugs. After treatment, the patient was cured and no recurrence has been observed.

The use of a one-step PCR method for the identification of Microsporum canis and Trichophyton mentagrophytes infection of pets

INTRODUCTION

Dermatophytes are a closely related group of keratinophilic fungi. They encompass important etiological agents of superficial fungal infections. These fungi are able to invade keratinized tissues of humans and animals, causing dermatophytosis (ringworm) of hair, nails or skin.

THE AIM

Traditional diagnostics of ringworm is based on morphological identification of cultured fungi and is time-consuming.

MATERIALS AND METHODS

In this study, we applied a method patented by Brillowska-Dabrowska and coworkers (Brillowska-Dąbrowska A, Saunte DM, Arenderup MC, 2007, Five-hour diagnosis of dermatophyte nail infections with specific detection of Trichophyton rubrum. J Clin Microbiol 45: 1200-1204) which involves extraction of fungal DNA and PCR amplification with pan-dermatophyte primers to confirm the presence of dermatophytes.

RESULTS

The method used here is able to confirm the presence of dermatophyte DNA in pure cultures in less than 5 hours.