Polymorphisms in the ITS rDNA regions for differentiating strains of the Trichophyton mentagrophytes complex in Sfax‐Tunisia

The Trichophyton mentagrophytes complex is the main cause of superficial mycoses in humans and animals. Molecular research has provided useful insights into the taxonomy of this complex to overcome the challenges with conventional diagnostics. The aim of this study was to identify, type and differentiate anthropophilic and zoophilic species of the T. mentagrophytes complex. Sixty clinical samples identified as T. mentagrophytes by morphological characteristics were isolated using polymerase chain reaction‐restriction fragment length polymorphism and sequence analysis of the internal transcribed spacer (ITS) regions. The identification of our strains by conventional methods was confirmed using polymerase chain reaction (PCR) sequencing in 93.34% of the cases. The strains under investigation were recategorised as T. rubrum (Tr2711). In addition, PCR products were independently digested with the restriction endonucleases, MvaI and HinfI, to produce a single dominant profile for T. interdigitale. ITS sequence analysis revealed a polymorphism in the ITS1 and 5.8S regions. Analysis of the consensus sequences distinguished four types of genotypes among our T. interdigitale species. Moreover, ITS type I was the dominant genotype characterising the anthropophilic variant of T. interdigitale. The phylogenetic study showed that only 5% of our strains were zoophilic. PCR sequencing was useful for distinguishing anthropophilic and zoophilic species of T. interdigitale, in which the differentiation is relevant because it helps to prescribe the correct treatment and to identify the surrounding source of infection.     

High terbinafine resistance in Trichophyton interdigitale isolates in Delhi,India harbouring mutations in the squalene epoxidase gene

In the last few years, infections caused by dermatophytes along with a concomitant increase in the number of difficult to treat cases have increasingly been recognised, indicating that dermatophytosis remains a challenging public health problem. The majority of infections are caused by Trichophyton rubrum and Trichophyton mentagrophytes complex. Terbinafine, an allylamine antifungal used orally and topically is considered to be a first‐line drug in the therapy of dermatophyte infections. Terbinafine resistance has been predominately attributed to point mutations in the squalene epoxidase (SQLE) target gene a key enzyme in the ergosterol biosynthetic pathway leading to single amino acid substitutions. Here, we report the largest series of 20 terbinafine‐resistant Trichophyton interdigitale isolates obtained predominately from cases of tinea corporis/cruris in three hospitals in Delhi, India exhibiting elevated MICs (4 to ≥32 μg/mL) to terbinafine and all harbouring single‐point mutations Leu393Phe or Phe397Leu in the SQLE gene. In 12 (60%) T. interdigitale isolates, the Phe397Leu substitution was observed, whereas in the remaining 8 (40%) isolates the substitution Leu393Phe was reported for the first time in T. interdigitale. Furthermore, 10 susceptible T. interdigitale isolates (0.125‐2 μg/mL) had a wild‐type genotype. Remarkably, considerably high terbinafine resistance rate of 32% was observed among 63 T. interdigitale isolates identified by sequencing of the internal transcribed spacer region. This high level of terbinafine resistance of Indian dermatophyte isolates is worrisome warranting antifungal susceptibility testing and mutation analysis for monitoring this emerging resistance.     

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

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

Perspectives on misidentification of Trichophyton interdigitale/Trichophyton mentagrophytes using internal transcribed spacer region sequencing: Urgent need to update the sequence database

The taxonomy of the dermatophytes has been revisited using a novel multilocus phylogenetic approach, and several neotypes and reference strains have been assigned for Trichophyton species. Single gene sequencing, that is the ITS region, for identification of highly related species T. mentagrophytes/T. interdigitale, warrant reassessment. The sequence database (Westerdijk and NCBI) needs to be updated as several incorrect/obsolete entries of reference and neotype strains of T. interdigitale/T. mentagrophytes hampers correct identification of this complex.     

Epizootic and epidemic dermatophytose outbreaks caused by Trichophyton mentagrophytes from rabbits in Portugal, 2015

We report an outbreak of dermatophytoses in rabbits, which was the origin of a dermatophytose epidemic in an agricultural school in central Portugal, affecting 15 people. Both the phenotypic characteristics and internal transcribed spacer (ITS) sequence of the dermatophytes isolated from the rabbits and patients were identical, suggesting that a single strain was responsible for both the epizootic and epidemic dermatophytoses and confirming that these two outbreaks were linked. The ITS sequences were also 100% identical to the ITS sequence of five strains isolated from rabbits in Greece and Italy, but different from that of Trichophyton mentagrophytes commonly isolated from dogs and cats. These results suggest that a particular T. mentagrophytes genotype could be prevalent in rabbits in southern Europe.     

High prevalence of superficial white onychomycosis by Trichophyton interdigitale in a Japanese nursing home with a geriatric hospital

A mycological survey on feet was performed in a nursing home with a geriatric hospital to ascertain the prevalence of tinea lesions. Of 100 subjects, comprising 62 in the nursing home and 38 in the geriatric wing, 70 were diagnosed with tinea pedis, tinea unguium (onychomycosis) or both of which 54 had onychomycosis alone, nine tinea pedis alone and seven had co‐existing onychomycosis and tinea pedis. The most common clinical type of onychomycosis was distal lateral subungual onychomycosis (DLSO) at 30 cases, followed by superficial white onychomycosis (SWO) at 23 cases. Fifteen strains of Trichophyton (T.) interdigitale isolated from 23 SWO patients comprised six molecular types (D2II, nine cases; C2II, two cases; four other types, one case of each), based on the non‐transcribed spacer region (NTS) of the ribosomal DNA. The pathogen of three other SWO cases was identified as T. rubrum. Direct physical contact between the subjects was unlikely because they were bedridden most of the time. Nine T. interdigitale strains were isolated from a bathtub used by patients on the floor with a high incidence of SWO alone, and all nine strains were D2II type, which suggests nosocomial infection. Consequently, the hospital infection control policy committee was consulted, bathing arrangements were changed, and nursing staff were educated about onychomycosis.     

Detection of dermatophytes in human nail and skin dust produced during podiatric treatments in people without typical clinical signs of mycoses

Pedicures are the most common cosmetic foot treatment. Many pedicurists and podiatrists suffer from respiratory infections and diseases such as asthma, sinusitis, chronic cough and bronchitis. Skin and nail dust may play an important role in the development of occupational diseases and the transmission of mycosis to other clients. To examine the presence of dermatophytes in nail and skin dust produced during podiatric treatments of people without typical symptoms of mycosis and to assess the epidemiological hazards of tinea pedis for podiatrists as well as other clients. Seventy‐seven samples underwent direct microscopy and culture. The results of direct microscopy were positive in 28/77 samples (36.36%) and doubtful in 3/77 (3.9%). Fungi were cultured from 36/77 samples (46.75%), including 8/77 (10.3%) positive for dermatophytes (Trichophyton rubrum‐6 isolates and Trichophyton mentagrophytes‐2). Material collected during podiatric treatments is potentially infected by pathogenic fungi; thus, there is a need to protect both workers who perform such treatments, as well as other clients, to prevent the transmission of pathogens in the Salon environment. Exposure to this occupational hazard may increase not only the risk of respiratory infections but also increase asthmatic or allergic reactions to Trichophyton.     

A clarion call for preventing taxonomical errors of dermatophytes using the example of the novel Trichophyton mentagrophytes genotype VIII uniformly isolated in the Indian epidemic of superficial dermatophytosis

An alarming pan Indian increase in the incidence of superficial dermatophytosis has been noticed over the past 5‐6 years. Recent studies have demonstrated emerging predominance of Trichophyton (T.) mentagrophytes as the causative organism in such cases. Interestingly, a distinct Indian genotype of T. mentagrophytes has been identified and recognised with the help of sequencing of the ITS region of the rDNA. That has, however, led to a basic confusion owing to the newly introduced taxonomy of dermatophytes in 2017. According to this most recently suggested classification and new taxonomy of dermatophytes, the former “T. mentagrophytes complex” is differentiated into T. mentagrophytes (zoophilic strains) and T. interdigitale (anthropophilic strains). We have noticed that in some recent studies the causative agent of the chronic, relapsing dermatophytosis outbreak in India has been described as T. interdigitale. In our opinion, it is very likely that these T. interdigitale strains isolated in Delhi and Chennai in India are indeed strains more closely related to the neotype of T. mentagrophytes and not strains of T. interdigitale. We therefore want to underscore the importance of a common nomenclature of species in accordance with the new taxonomy of dermatophytes. This would most likely facilitate better understanding of the issue amongst dermatologists and microbiologists in general. Mistaken identification of Trichophyton isolates not limited to India is very likely to occur due to the lack of appropriate molecular diagnosis which in turn is based on the already published data that presumably wrongly identify one species instead of the other.     

Molecular epidemiology and in vitro antifungal susceptibility of Trichophyton schoenleinii,agent of tinea capitis favosa

Trichophyton schoenleinii is an anthropophilic dermatophyte usually causing tinea favosa. Only few studies have provided data on molecular epidemiology and antifungal profiles of this fungus due to its limited prevalence after 1950s. Forty‐nine strains from Asia (n = 27), Africa (n = 10), Europe (n = 10) and from unknown regions (n = 2) were analysed with amplified fragment length polymorphism fingerprinting (AFLP) to reveal intraspecific genetic diversity in this dataset. Amplified fragment length polymorphism fingerprinting genotyping revealed five clusters which did not correspond to geographic origins or clinical characteristics. Additionally, in vitro antifungal susceptibility to seven antifungals was provided for all strains. Terbinafine, ketoconazole, miconazole and itraconazole proved to be the most effective drugs, followed by griseofulvin. No correlation between genotypes and differences in antifungal susceptibility was observed. It is concluded that the AFLP groups are lineages within a single species.     

Would you like to purchase a rodent with dermatophytes?

The zoophilic dermatophyte Trichophyton benhamiae has received attention due to increasing infections in human in recent years. Trichophyton benhamiae has been found on asymptomatic rodents from pet shops in several countries posing a potential risk for transmission to humans. The aim of this study was to determine the prevalence of positive dermatophyte cultures from rodents in Danish pet shops in order to clarify the magnitude of potential sources of zoophilic infections and to prevent further spread. Specimen sampling was performed in 17 Danish pet shops using the brush technique (MacKenzie technique). After incubation, cultures were sent to ITS DNA sequencing for molecular species identification. Pet shop employees were asked to fulfil a five‐question survey regarding purchase and procedures of diseased animals. A total of 98 animals were sampled (N = 32 rabbits, N = 32 guinea pigs and N = 34 hamsters). Trichophyton benhamiae was found in 14/98 samples (14%); 12/32 guinea pigs (38%) were positive with T benhamiae, 2/34 (6%) hamsters and 0/32 rabbits (0%). We found that hamsters and particularly guinea pigs from Danish pet shops are common asymptomatic carriers of the dermatophyte T benhamiae. Although a larger study is warranted to test this postulate, and it raises the question if infection control measures should be implemented in pet shops.     

A clinico‐epidemiological study on tinea gladiatorum in Iranian wrestlers and mat contamination by dermatophytes

Dermatophytosis is still being considered as one of the major public health problems in wrestlers. Objectives: To identify the prevalence, clinical pattern, aetiological agents and the predominant transmission route of dermatophytoses in Iranian wrestlers, a study was carried out in 2008. In total, 270 wrestlers from eight wrestling salons were evaluated. Classical mycological techniques were performed on 135 skin scraping samples of 110 wrestlers suspicious for dermatophytoses and 240 touch preparation samples of wrestling mats. Diagnosis of the fungus type was made based on macroscopical and microscopical characteristics of the colonies. 19.2% of the evaluated wrestlers were inflicted with tinea gladiatorum. The head and neck were the most prevalent (36.5%) areas of involvement, followed by arms and forearms (28.8%), trunk (21.2%), as well as groin and knee (13.5%). The mean age of patients was 21 years and the most frequent age group was 10–19 years (51.9%). Trichophyton tonsurans was the most frequently isolated species representing 82.7% of isolates, followed by T. rubrum (5.8%), T. mentagrophytes var. interdigitale and Epidermophyton floccosum (3.8% each), and T. mentagrophytes var. mentagrophytes and T. verrucosum (1.9% each). Of 24 wrestling mats surveyed, 33.3% were heavily contaminated with T. tonsurans. Tinea gladiatorum in Iran is a common phenomenon among wrestlers, transmission pattern of which appears to be through man‐to‐man and mat‐to‐man contact. Furthermore, the clinical features of the disease are not consistent with those of the general population of Iran.     

Onychomycosis observed in children over a 20‐year period

There are few reports studying the aetiology of onychomycosis in children in Spain. To study childhood dermatophyte onychomycosis, a retrospective study of children was carried out, who were <16 years of age with dermatophyte onychomycosis diagnosed between 1987 and 2007. Of 4622 nail samples from 3550 patients, 218 came from 181 children up to 16 years old. Onychomycosis caused by dermatophytes was demonstrated in 28 (15.5%) cases. Trichophyton rubrum (18 cases) was the most prevalent species, followed by Trichophyton tonsurans (five cases), Trichophyton mentagrophytes var. interdigitale (four cases) and Trichophyton mentagrophytes var. mentagrophytes (one case). Concomitant dermatophytosis at other locations was confirmed in seven cases (25%). Toenail onychomycosis was associated with tinea pedis in five cases. Distal and lateral subungual onychomycosis was the most common clinical pattern. The superficial white type was found in two cases of toenail onychomycosis caused by T. rubrum and T. tonsurans. During the period of study, only 5.1% of all investigated people were children up to 16 years. The prevalence of onychomycosis tended to increase over the years and represented 15.5% of all nail dystrophies in children. Therefore, dermatologists must consider onychomycosis in the differential diagnosis of nail alterations in children and always perform a mycological study to confirm the diagnosis.     

Trichophyton verrucosum infection in cattle farms of Umbria (Central Italy) and transmission to humans

Trichophyton verrucosum is the most common ringworm agent in cattle. Epidemiology of cattle dermatophytoses in Central Italy is not clear. Its diffusion among cattle and herdsmen was investigated in 20 Umbrian farms, Central Italy. Hairs and scales were taken from 395 animals and 31 workers. Typical ringworm was present in 71.7% of cattle under 6 months and in 11% of animals over 6 months. T. verrucosum was isolated from 98.9% of symptomatic heads and was the most prevalent dermatophyte in all herds investigated (isolated in 18 of the 20 farms). T. mentagrophytes var. mentagrophytes was found in 16 symptomatic and in eight asymptomatic young animals. Prevalence of asymptomatic carriers of both species was significantly higher in young heads (21.1% vs. 8.1%) and the age below 6 months was the only statistically significant risk factor associated with dermatophytosis. About the workers, all the 14 men with lesions were positive for T. verrucosum; copresence of T. verrucosum and Microsporum gypseum was noticed in one case. Results indicate a high diffusion of T. verrucosum among both animals and humans in Umbrian farms and confirm the dermatophyte infection as a public health problem. Periodic epidemiological surveys, treatment of sick livestock and workers, cleaning/sanitisation of herds and vaccination programmes may be useful in controlling the infection.     

The current Indian epidemic of superficial dermatophytosis due to Trichophyton mentagrophytes—A molecular study

The disease burden of chronic‐relapsing and therapy‐refractory superficial dermatophytosis dramatically increased in India within the past 5‐6 years. In order to evaluate the prevalence of this trend, 201 skin scrapings were collected from patients from all parts of India and were tested for dermatophytes using both fungal culture and a PCR‐ELISA directly performed with native skin scrapings. Fungal culture material was identified by genomic Sanger sequencing of the internal transcribed spacer (ITS) region and the translation elongation factor (TEF)‐1α gene. In total, 149 (74.13%) out of the 201 samples showed a dermatophyte‐positive culture result. Out of this, 138 (92.62%) samples were identified as Trichophyton (T.) mentagrophytes and 11 (7.38%) as Trichophyton rubrum. The PCR‐ELISA revealed similar results: 162 out of 201 (80.56%) samples were dermatophyte‐positive showing 151 (93.21%) T mentagrophytes‐ and 11 (6.79%) T rubrum‐positive samples. In this study, we show for the first time a dramatic Indian‐wide switch from T rubrum to T mentagrophytes. Additionally, sequencing revealed a solely occurring T mentagrophytes “Indian ITS genotype” that might be disseminated Indian‐wide due to the widespread abuse of topical clobetasol and other steroid molecules mixed with antifungal and antibacterial agents.     

Asymptomatic groin dermatophyte carriage detected during routine gynaecologic examinations

We investigated the epidemiological characteristics of both symptomatic and asymptomatic dermatophytic groin infections in 1970 women (age: 36.2 ± 12.5) during routine gynaecologic examinations. Bilateral groin samples were collected with sterile cotton swabs premoistened with sterile physiological saline. The samples were then separately inoculated onto Sabouraud glucose agar. Fungi were identified by sequencing the rDNA internal transcribed spacer region. Dermatophytes were recovered from five patients (four Trichophyton rubrum and one Arthroderma vanbreuseghemii, 0.25%) with a diagnosis of asymptomatic carriers (four) and tinea inguinalis (one). In one case, groin carriage converted into tinea inguinalis after 3 weeks. Analysis of risk factors indicated that patients of at least 49 years were more likely to be positive for dermatophyte isolation (P = 0.002). In conclusion, groin dermatophyte carriage is more common than tinea inguinalis and can potentially convert into a symptomatic infection.     

Inflammatory Tinea capitis: a 12‐year study and a review of the literature

Inflammatory Tinea capitis (TC) is a rare form of TC. The aim of this study was to review epidemiological, clinical and mycological profile of inflammatory TC. We present a retrospective study (1999–2010), enrolled all the cases of inflammatory TC observed at a referral hospital in the northern Tunisia. One hundred and twenty‐one patients with inflammatory TC, 83 male patients (68.6%) and 38 female patients (31.4%) were enrolled. The mean age was about 8 years. A majority of TC (71.9%) were in patients lesser than 10 years of age. Positive family history and contact with animals were noted in seven and 35 cases respectively. Direct examination was positive in 110 cases (59 ectothrix, 51 endothrix) and positive cultures were obtained in 105 patients (49 Trichophyton violaceum, 31 Microsporum canis, 13 Trichophyton interdigitale complex, 12 Trichophyton verrucosum). Systemic treatment was carried out in 115 patients with griseofulvin, in one with terbinafine. A complete recovery was noted in 88 cases; and persistent alopecia in 28 cases. The inflammatory TC is rare, but more common in rural families. The disease mostly affected male genders (68.6%) and T. violaceum remains the common pathogen of inflammatory TC in northern Tunisia.     

Inflammatory tinea capitis mimicking dissecting cellulitis in a postpubertal male: a case report and review of the literature

Tinea capitis in postpubertal patients is unusual and may be misdiagnosed as dissecting cellulitis. We report a case of a healthy 19‐year‐old Hispanic male presenting with a 2‐month history of a large, painful subcutaneous boggy plaque on the scalp with patchy alopecia, erythematous papules, cysts and pustules. Although initially diagnosed as dissecting cellulitis, potassium hydroxide evaluation (KOH preparation) of the hair from the affected region was positive. A punch biopsy of the scalp demonstrated endothrix consistent with tinea capitis, but with a brisk, deep mixed inflammatory infiltrate as can be seen with chronic dissecting cellulitis. Fungal culture revealed Trichophyton tonsurans, and a diagnosis of inflammatory tinea capitis was made. The patient was treated over the course of 17 months with multiple systemic and topical antifungal medications, with slow, but demonstrable clinical and histopathological improvement. A rare diagnosis in adults, clinicians should have a high index of suspicion for this condition in an adult with an inflammatory scalp disorder not classic for dissecting cellulitis or with a recalcitrant dissecting cellulitis. Prompt, appropriate diagnosis and treatment is necessary to prevent the long‐term complications of scarring alopecia.     

Connubial tinea gladiatorum due to Trichophyton mentagrophytes

Trichophyton mentagrophytes is one of the most common dermatophytes causing cutaneous human fungal disease worldwide. Pubic and/or vulvar localisation of dermatophytosis has rarely been reported and may often be misdiagnosed as bacterial infections. We present a connubial case of severe inflammatory tinea in the genital region caused by T. mentagrophytes. The case illustrates the importance of getting material for cultivation before treatment and emphasises the difficulty of diagnosis and treatment of fungal infections in the genital region.     

Dermatophytoses in Würzburg 1976–1985*,**

Summary: In the decade 1976–1985, 8973 dermatophytes were isolated from patients at the University Dermatological Clinic, Würzburg. Trichophyton rubrum comprised 73.9% und Trichophyton mentagrophytes 19.6% of all isolates, while isolation rates of all other species of dermatophytes were under 5%. The most common dermatomycoses were tinea pedum in 43.8% and tinea unguium pedum in 28.8% of all localizations of tinea. A comparison of our results with those of an investigation in the same clinic undertaken between 1956–1958 (Veltman et al.) reveals that the epidemiological shift from T. mentagrophytes to T. rubrum as the most common causative agent of dermatomycoses, a shift that has been observed world-wide, must have taken place in Würzburg between 1959 and 1975. Zusammenfassung: Im Zehnjahreszeitraum 1976–1985 wurden von Patienten der Universitäts-Hautklinik Würzburg 8973 Dermatophyten isoliert. Trichophyton rubrum machte 73,9% und Trichophyton mentagrophytes 19,6% alter Dermatophytenisolate aus, während alle übrigen Dermatophytenspezies in unter 5% isoliert wurden. Die häufigsten Dermatomykosen waren die Tinea pedum mit 43,8% und die Tinea unguium pedum mit 28,8% aller Tinea-Krankheiten. Der Vergleich mit einer Untersuchung an unserer Klinik aus den Jahren 1956–1958 (Veltman und Mitarb.) ergibt, daß die weltweit beobachtete epidemiologische Verschiebung von T. mentagrophytes zu T. rubrum als dem häufigsten Erreger von Dermatomykosen in Würzburg zwischen 1959 und 1975 stattgefunden haben muß.