Trichophyton indotineae and other terbinafine-resistant dermatophytes in North America

Dermatophyte infections (a.k.a. ringworm, tinea) affect an estimated 20%-25% of the world's population. In North America, most dermatophytoses are caused by Trichophyton rubrum or Trichophyton mentagrophytes species complexes. Severe and antifungal-resistant dermatophytoses are a growing global public health problem. A new species of the T. mentagrophytes species complex, Trichophyton indotineae, has recently emerged and is notable for the severe infections it causes, its propensity for antifungal resistance, and its global spread. In this issue of the Journal of Clinical Microbiology, C. F. Cañete-Gibas, J. Mele, H. P. Patterson, et al. (J Clin Microbiol 61:e00562-23, 2023, https://doi.org/10.1128/JCM.00562-23) summarize the results of speciation and AFST performed on North American dermatophyte isolates received at a fungal diagnostic reference laboratory. Within their collection, 18.6% of isolates were resistant to terbinafine (a first-line oral antifungal for dermatophytoses), and similar proportions of T. rubrum and T. indotineae demonstrated terbinafine resistance. The authors also found that T. indotineae has been present in North America since at least 2017. These findings highlight the importance of increased surveillance efforts to monitor trends in severe and antifungal-resistant dermatophytoses and the need for antifungal stewardship efforts, the success of which is contingent upon improving laboratory capacity for dermatophyte speciation and AFST.

Internal Transcribed Spacer Region Typing of Trichophyton interdigitale Isolated from Japanese Patients

Trichophyton interdigitale, an anthropophilic species, is one of the main causative agents of tinea unguium and tinea pedis. T. interdigitale and the zoophilic species T. mentagrophytes are morphologically and physiologically very similar. Isolates of the T. interdigitale/T. mentagrophytes complex from around the world have been classified into more than 10 internal transcribed spacer (ITS) genotypes. In this study, we isolated T. interdigitale from Japanese patients and investigated which ITS type was more common. The ITS regions of 29 clinical isolates of T. interdigitale and one clinical isolate of T. mentagrophytes were sequenced. The phylogenetic analysis of the ITS region sequences revealed that the 29 isolates of T. interdigitale belong to ITS type II of T. interdigitale. The one clinical isolate of T. mentagrophytes was in the same cluster with ITS type II* of T. mentagrophytes. One terbinafine-resistant strain of T. interdigitale also belonged to ITS type II of T. interdigitale.

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.

[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.

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.

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.

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.

Mating type gene (MAT1-2) of Trichophyton verrucosum

Trichophyton verrucosum is a zoophilic dermatophyte species that is the most frequent etiologic agent of bovine dermatophytosis throughout the world. Since no teleomorph of T. verrucosum has been found, polymerase chain reaction (PCR) analysis on the genome of T. verrucosum isolated from the Czech Republic and Japan was performed to confirm the presence of a mating type locus in the genome of the fungus and to clarify its classification and ecological characteristics. The mating type gene (MAT1-2) allele was detected by PCR analysis in all 22 isolates (four isolates from the Czech Republic and 18 isolates from Japan). The nucleotide sequence of the region exhibited 99-100 % identity among all isolates, including the reference strain of T. verrucosum. Phylogenetic analysis revealed that the sequences of the internal transcribed spacer region at the MAT1-2 locus clustered together in the isolates examined, forming a branch distinct from that of the other dermatophyte species. These results suggest that T. verrucosum is a clonal offshoot that has drifted away from Arthroderma benhamiae.

Genotype Analysis of the Variable Internal Repeat Region in the rRNA Gene ofTrichophyton tonsuransIsolated from Japanese Judo Practitioners

Tinea capitis due to Trichophyton tonsurans is currently epidemic among Japanese Judo practitioners. T. tonsurans has seven genotypes in a variable internal repeat (VIR) region of the rRNA gene. All 101 isolates obtained from Japanese Judo practitioners had the identical genotype. This suggests that a specific genotype strain occurs throughout Japan.

[Influence of the ecological group on the in vitro antifungal susceptibility of dermatophytic fungi]

BACKGROUND

Dermatophytes can be divided into geophilic (soil), zoophilic (animals) and anthropophilic (humans) strains, depending on the source of the keratin that they use for nutritional purposes.

AIMS

The in vitro susceptibility of clinical isolates of dermatophyte fungi has been studied in the 3 ecological groups with several antifungal agents for the topical management of dermatophytoses in order to determine their relationship with the ecological group.

METHODS

A standardised dilution micromethod in a liquid medium was used for the determination of the in vitro antifungal activity of 9 topical antifungal drugs: amorolfine (AMR), bifonazole (BFZ), clotrimazole, econazole, ketoconazole, miconazole, oxiconazole, terbinafine (TRB) and tioconazole. The in vitro activity was obtained against 124 clinical isolates of dermatophyte moulds from the anthropophilic, zoophilic and geophilic ecological groups.

RESULTS

The in vitro antifungal activity was different depending on the ecological group, although a species-dependent profile was also observed.

CONCLUSIONS

Azole derivatives showed a similar antifungal profile, being more active against anthropophilic dermatophytes > zoophilic > geophilic. Activity of TRB and AMR was different from that of azole derivatives (zoophilic > anthropophilic > geophilic). A higher in vitro antifungal activity against the 3 ecological groups was observed with TRB and AMR, whilst BFZ was the less active drug.

Molecular epidemiology of Trichophyton tonsurans strains isolated in Japan between 2006 and 2010 and their susceptibility to oral antimycotics

Trichophyton tonsurans has been isolated among judo practitioners, wrestlers, and sumo wrestlers during an epidemic of tinea corporis and tinea capitis in Japan. A previous study using restriction fragment length polymorphism (RFLP) analysis of the non-transcribed spacer (NTS) region of the ribosomal RNA gene revealed that different sources for the causative fungus in epidemics among judo practitioners and among wrestlers. Many different fungal strains have since been isolated from practitioners of these sports. The present study evaluated fungal characteristics of strains newly isolated between July 2006 and December 2010 using this molecular method. PCR-RFLP analysis using MvaI and AvaI was performed on 263 strains, composed of 186 isolates from judo practitioners, 32 from wrestlers, 30 from sumo wrestlers, 5 from other sports, 7 from family members or friends of the sports practitioner patients, and 3 from sporadic (non-epidemic) cases. Four molecular types, NTS I, II, III, and VII were detected. Of these, NTS I was the most predominant, occurring in 243 of 263 strains (92.4%). All of the 30 strains isolated from sumo wrestlers were classified as NTS I, suggesting that the epidemic among sumo wrestlers originated from an earlier epidemic among judo practitioners. Thirteen strains were classified as NTS II; all were related to wrestling and were isolated mainly from Chubu and Kansai areas in the central part of Honshu island. NTS III was detected in 6 strains, and one strain classified as NTS VII was isolated from a sporadic case of tinea capitis in a Peruvian immigrant. The minimum inhibitory concentrations (MICs) of terbinafine, itraconazole, fluconazole, and griseofulvin on 10 strains of NTS I and NTS II and 4 strains of NTS III were examined; there were no differences in MIC between these molecular types.

[A tinea incognito case caused by Trichophyton rubrum with clinical and mycological cure and review of the literature]

Tinea incognito is the result of lack of diagnosis of dermatophyte infection of the glabrous skin and the misuse of steroids or calcineurin inhibitors. In this case report a 20-years-old female patient diagnosed as tinea incognito and Trichophyton rubrum isolated from her skin lesions, was presented. The patient suffered from an itchy skin lesion on her neck and right breast. Physical examination revealed and plaques with erythema and papules on neck and breast area. The patient had used several corticostero- ids suggested by dermatologists for 10 months. Direct microscopic examination of the skin scrapings with 10% potassium hydroxide preparation revealed fungal elements and Trichophyton rubrum was isolated in culture. Use of corticosteroids was ceased and terbinafine (250 mg tb and cream) therapy was initiated to continue for four weeks. Following treatment, total clinical and mycological cure was established. It was concluded that tinea incognito which was not a rare clinical entity, could be presented in various clinical forms and usually resulted from the wrong treatment modalities. Thus atypical erythematous plaques should be investigated in terms of presence of fungi and treated accordingly to establish total clinical and mycological cure.

Prevalence of tinea capitis and the causative agent among school children in Gondar, North West Ethiopia

BACKGROUND

Tinea capitis is a worldwide public health problem that poses specific therapeutic challenge. This dermatophytosis of the scalp is characteristically a fungal infection affecting children between 5 and 15 years of age. A decision on treatment of tinea capitis requires identification of the specific causative fungal agent or at least establishment of the prevalence of a given dermatophyte in a given community.

OBJECTIVE

to estimate the prevalence of tinea capitis, assess predisposing risk factors and identify the causative fungal agent in school children in north Gonder zone, Northwest Ethiopia.

METHODS

This was a cross sectional study conducted in two elementary schools in Gondar town. Clinico-dermatological data and questionnaire on socio-demographic information, living and hygienic conditions were collected. Mycological investigation was done by microscopic examination culture.

RESULTS

A total of 372 students were screened for Tinea capitis infection, 262 from Meseret elementary school and 110 from Chechela elementary school. Among these, 61% (n = 227) were female and 39% (n = 145) were male. The median age was 10 years old, 98% of the study subjects were within the age range of 5 to 15. From the screened 372 children 47.5% (n = 177) were clinically suspected for Tinea capitis and 174 scalp samples were collected Microscopic examination in KOH (10%)-wet-mount preparation revealed 65.5% (n = 14) had fungal elements (hyphae and/or arthroconidia) in their clinical samples. Out of 174 specimen 50.0% (87) were culture positive. 33.9% (59) were contaminated and in 16.0% (28) were culture negative. From the positive samples 86.2% (75) were identified as Trichophyton violaceum. The rest 13.8% (12) were further sub-cultured at 37 degrees C and studied morphologically, and identified as Trichophyton verrucosum.

CONCLUSION

A high prevalence of Tinea capitis caused by T. violaceum was found in school children in Gondar. Ethiopia. Provisions for prevention and control should be set in the schools focused on hygiene control and health education.

Tinea incognito due to Trichophyton mentagrophytes

Tinea incognito is a dermatophytosis of atypical clinical character, usually misdiagnosed and treated with corticosteroids. We report a case of tinea faciei modified by high potency topical corticosteroids in a 54-year-old woman. Deep, intense inflammatory plaque with boggy, pustular surface located on the right cheek was found. Direct microscopy and culture confirmed dermatophytosis and led to the identification of Trichophyton mentagrophytes var. mentagrophytes. Complete resolution occurred after treatment with oral terbinafine.

A large outbreak of Trichophyton tonsurans among health care workers in a pediatric hospital

BACKGROUND

Although Trichophyton tonsurans remains a major cause of dermataophytoses in US children, nosocomial spread may go unrecognized in health care settings. We describe a staff outbreak of T tonsurans infection among health care workers in a freestanding pediatric hospital.

METHODS

Epidemiologic evaluation (retrospective and prospective) was performed in the health care providers and ancillary staff assigned to a 27-bed inpatient medical unit in which the suspected outbreak occurred.

RESULTS

Twenty-one individuals, including staff, a hospital volunteer, and a patient, developed tinea corporis during a 5-month period. All infections coincided with multiple admissions of a 2-year-old suspected index patient who demonstrated persistent infections of the scalp and arm. Fungal isolates obtained from the index patient and affected staff (when available) were subjected to multilocus strain typing, which revealed an identical genetic match between the index case and infected hospital personnel.

CONCLUSION

T tonsurans can spread widely among staff members caring for children with recalcitrant dermatophyte infections. Recognition that workplace transmission may be the etiology of a succession of infections occurring in a single inpatient unit is necessary to limit the number of infected individuals.

Dermatophyte infections in Cairo, Egypt

In this study, we examined dermatophyte infections in patients referred to the Department of Dermatology, EL-Houd El-Marsoud Hospital, Cairo, during March 2004 to June 2005. Of 506 patients enrolled in this investigation, 403 (79.6%) were clinically diagnosed as having dermatophytoses (age range 6-70 years; males 240; females 163). Species identification determined by observation of their macroscopic and microscopic characteristics was complemented with sequencing of the internal transcribed spacer ITS1-5.8S-ITS2 rDNA region. The most common dermatophyte infection diagnosed was tinea capitis (76.4%), followed by tinea corporis (22.3%) and tinea unguium (1.2%). The most frequently isolated dermatophyte species was Trichophyton violaceum, which accounted for most (71.1%) of all the recovered dermatophytes, followed by Microsporum canis (21.09%), Trichophyton rubrum (6.2%), and Microsporum boullardii (0.49%); both Epidermophyton floccosum and Trichophyton tonsurans were each only rarely isolated (0.24%).

[Trichophyton violaceum: an emerging pathogen]

Population changes taking place in recent years, such as more frequent travel to endemic areas, immigration, and international adoptions, have all contributed to a resurgence of certain pathogens in our geographical area. This is the case of Trichophyton violaceum. A retrospective review was made of all cases of superficial mycosis caused by T. violaceum in patients receiving in-hospital treatment during the years 2000 to 2006. This microorganism accounted for 18.5% of the 275 dermatophytes isolated during the above-mentioned period. In 96% of T. violaceum infections, the lesion manifested as tinea capitis, and all the patients were foreigners. We report in increase of tinea capitis caused by T. violaceum among pediatric patients that appears to be directly related to immigration.

Epidemiology of sporadic (non-epidemic) cases of Trichophyton tonsurans infection in Japan based on PCR-RFLP analysis of non-transcribed spacer region of ribosomal RNA gene

A number of cases of Trichophyton tonsurans infection have been reported among sportsmen and women participating in wrestling, judo, and sumo wrestling in Japan, but there have also been sporadic reports of cases with no history of contact with these sports. A molecular method using restriction enzyme analysis of PCR-amplified fragments targeting the non-transcribed spacer region (NTS) of ribosomal RNA gene in fungal nuclei was applied to T. tonsurans strains isolated from sporadic cases in Japan. Five of 6 molecular types recorded in Japan, i.e., NTS types I, II, IV, V, and VI, and two new types, designated NTS VII and NTS VIII, were observed among 10 strains isolated from sporadic cases. The NTS IV strains, considered not to be related to the present epidemic, were found to be the most prevalent molecular type accounting for 4 of the 10 strains isolated. NTS I was the most prevalent type in the current epidemic in Japan, but it was cultured from only one patient who was later noted to be the daughter of a retired judo practitioner. Four subjects had histories of living abroad and were considered to have been infected outside Japan. The strains in these cases were NTS II, V, VI, and VII. The results of this study suggested that the NTS IV strains were originally present in Japan at a low incidence, but that there has been a recent influx of NTS I, II, V, VI, and VII from abroad, which has been accompanied by the secondary spread of strains from wrestlers and practitioners of martial arts to the general community.

Domain II hairpin structure in ITS1 sequences as an aid in differentiating recently evolved animal and plant pathogenic fungi

The hypothesis that ITS structural features can be used to define fungal groups, where sequence analysis is unsatisfactory, was examined in plant and animal pathogenic fungi. Structural models of ITS1 regions were predicted for presumed closely related species in Colletotrichum and Trichophyton anamorphs of Arthroderma species. Structural alignment of models and comparison with ITS sequence analysis identified a variable region in a conserved hairpin formed from a common inverted repeat. Thirteen different hairpin structure models were obtained for Colletotrichum species and five different models were obtained for Trichophyton species. The different structure types could be matched to individual species and species complexes as defined by ITS sequence analysis.

[Investigation of the agents and risk factors of dermatophytosis: a hospital-based study]

The aims of this study were the detection of distribution of dermatophyte species isolated from the clinical samples of patients with dermatophytosis and the evaluation of risk factors for the development of dermatophytosis. A total of 441 skin, nail and scalp/hair specimens obtained from 301 patients (151 were male; age range 2 months-80 years, median 42 years) and 884 foot and hand skin and nail specimens obtained from 221 control subjects (110 were male; age range 5-75 years, median 36 years) were included to the study between the period of January to December 2005. All the samples have been evaluated by direct microscopic (DM) examination and by culture. A total of 121 (40.2%) patients yielded positivity for dermatophytes, of them 63 were positive by both DM and culture methods, seven were only culture positive, and 51 were only DM positive. Nine (9.8%) of 92 culture positive samples from 70 patients were found negative in DM, while 85 (50.6%) of 168 DM positive samples from 114 patients were negative in culture. 23.5% (12/51) of DM positive but culture negative patients were given antifungal therapy previously. The most prominent species isolated from the cultures were Trichophyton rubrum with a rate of 68.4% (63/92), followed by T. mentagrophytes (18.4%); T. violaceum (3.3%); T. verrucosum, T. tonsurans and Epidermophyton floccosum (2.2% for each); T. schoenleini, Microsporum canis and Trichophyton sp. (1.1% for each). Of the patient samples whose cultures were positive, 45% were from the foot skin. The presence rate of dermatophytes in controls was found as 3.2% (7/221); T. rubrum was isolated from the foot skin of five and T. mentagrophytes was isolated in toenail of two control subjects. About 42% of the samples belonged to the patients who admitted to hospital between December to February period. The evaluation of the risk factors revealed that presence of trauma, pet contact, ritual cleansing and diabetes mellitus had no effect on the development of dermatophytoses, however the presence of fungal infection in the family, male gender, some professions (being farmer, worker and retired), and the use of immunosupressive drugs have been found to increase the risk of dermatophytosis. The number of cases with dermatophytoses started to increase beginning from the age of 20 and peaked in the ages between 40-59 years old. As a result T. rubrum was determined as the most frequently isolated dermatophyte and tinea pedis was the most frequently observed clinical form in our hospital, emphasizing the importance of early diagnosis and effective treatment in superficial fungal infections which have high morbidity.