Ocorrência de dermatófitos em amostras de unhas, pés e mãos coletadas de estudantes universitários

Este trabalho teve como objetivo, avaliar a presença de dermatófitos, especificamente em unhas, pés e mãos de estudantes universitários com e sem lesões sugestivas de dermatofitose. Foram coletadas 280 amostras dessas regiões, das quais 31 (11,1%) apresentaram positividade apenas pelo exame direto, e 20 (7,1%) tiveram, além do exame direto positivo, crescimento de dermatófito, mediante cultivo da amostra biológica. T. rubrum foi o dermatófito isolado com maior freqüência (80%), seguido por T. mentagrophytes (20%). Considerando os sítios analisados neste trabalho, a ocorrência de dermatófitos foi observada em 10,4% nas unhas dos pés, 5% nas escamas de pés, 2,5% nas unhas das mãos e apenas 0,4% nas escamas das mãos.

Forty-eight-hour diagnosis of onychomycosis with subtyping of Trichophyton rubrum strains

A novel strategy for the molecular identification of fungal agents of onychomycosis (including Trichophyton rubrum) has been designed based on the use of species-specific and universal primers in conjunction with a commercial kit that allows the extraction of DNA directly from the nail specimens. The microsatellite marker T1, which is based on a (GT)n repeat, was applied for the species-specific identification of Trichophyton rubrum. To evaluate how often Scopulariopsis spp. are detected in nail specimens, a second primer pair was designed to amplify specifically a 336-bp DNA fragment of the 28S region of the nuclear rRNA gene of S. brevicaulis and closely related species. Other fungal species were identified using amplification of the internal transcribed spacer (ITS) region of the rRNA gene, followed by restriction fragment length polymorphism analysis or sequencing. In addition, polyacrylamide gel separation of the T1-PCR product allowed subtyping of T. rubrum strains. We studied 195 nail specimens (the "nail sample") and 66 previously collected etiologic strains (the "strain sample") from 261 onychomycosis patients from Bulgaria and Greece. Of the etiologic agents obtained from both samples, T. rubrum was the most common organism, confirmed to be present in 76% of all cases and serving as the sole or (rarely) mixed etiologic agent in 199 of 218 cases (91%) where the identity of the causal organism(s) was confirmed. Other agents seen included molds (6% of cases with identified etiologic agents; mainly S. brevicaulis) and other dermatophyte species (4%; most frequently Trichophyton interdigitale). Simultaneous infections with two fungal species were confirmed in a small percentage of cases (below 1%). The proportion of morphologically identified cultures revealed by molecular study to have been misidentified was 6%. Subtyping revealed that all but five T. rubrum isolates were of the common type B that is prevalent in Europe. In comparison to microscopy and culture, the molecular approach was superior. The PCR was more sensitive (84%) than culture (22%) in the nail sample and was more frequently correct in specifically identifying etiologic agents (100%) than microscopy plus routine culture in either the nail or the strain samples (correct culture identifications in 96% and 94% of cases, respectively). Using the molecular approach, the time for diagnosing the identity of fungi causing onychomycosis could be reduced to 48 h, whereas culture techniques generally require 2 to 4 weeks. The early detection and identification of the infecting species in nails will facilitate prompt and appropriate treatment and may be an aid for the development of new antifungal agents.

Strain differentiation of Trichophyton rubrum by randomly amplified polymorphic DNA and analysis of rDNA nontranscribed spacer

Trichophyton rubrum is the most common pathogen causing dermatophytosis. Molecular strain-typing methods have recently been developed to tackle epidemiological questions and the problem of relapse following treatment. A total of 67 strains of T. rubrum were screened for genetic variation by randomly amplified polymorphic DNA (RAPD) analysis, with two primers, 5′-d[GGTGCGGGAA]-3′ and 5′-d[CCCGTCAGCA]-3′, as well as by subrepeat element analysis of the nontranscribed spacer of rDNA, using the repetitive subelements TRS-1 and TRS-2. A total of 12 individual patterns were recognized with the first primer and 11 with the second. Phylogenetic analysis of the RAPD products showed a high degree of similarity (>90 %) among the epidemiologically related clinical isolates, while the other strains possessed 60 % similarity. Specific amplification of TRS-1 produced three strain-characteristic banding patterns (PCR types); simple patterns representing one copy of TRS-1 and two copies of TRS-2 accounted for around 85 % of all isolates. It is concluded that molecular analysis has important implications for epidemiological studies, and RAPD analysis is especially suitable for molecular typing in T. rubrum.

Real-time PCR TaqMan assay for detectingTrichophyton tonsurans, a causative agent of tinea capitis, from hairbrushes

Tinea capitis caused by Trichophyton tonsurans is currently an epidemic in the United States, Europe, and Japan, and the cultivation of this microorganism is necessary for a definitive diagnosis. We recently developed a real-time PCR TaqMan assay as a culture-independent method for the rapid detection of T. tonsurans from hairbrushes.

Arthroderma olidum, sp. nov. A new addition to theTrichophyton terrestrecomplex

In 1981, four fungal isolates from hair of the European badger (Meles meles) were examined by Dr Phyllis Stockdale at the Commonwealth Mycological Institute, Kew, and deposited in the UK National Collection of Pathogenic Fungi as an undescribed member of the Trichophyton terrestre complex. The present paper formalizes the complete description of a new ascomycete taxon, Arthroderma olidum following successful recent attempts to re-isolate the same fungus from the soil of Badger holes in South West England. Furthermore, using ribosomal RNA gene sequencing, we show that the asexual form of A. olidum is conspecific with the recently described Trichophyton eboreum1 isolated from a human skin specimen in Germany.

Aetiological agents of tinea capitis in Tehran (Iran)

A total of 1568 patients with suspected tinea capitis were examined for causative fungal agents between 1994 and 2001. Laboratory examination confirmed tinea capitis in 209 patients. Males were affected more frequently (67.5%) than females (32.5%) and in both sexes, those who were 3-11 years old, were more infected. Trichophyton violaceum was the most common aetiological agent (37.3%) followed by Trichophyton schoenleinii (21.5%), Microsporum canis (18.6%), Trichophyton verrocosum (14.8%), Trichophyton tonsurans (5.3%), Trichophyton rubrum (1%), Microsporum gypseum (1%) and Trichophyton mentagrophytes (0.5%). A higher incidence of the disease was found to be correlated with larger family and class size. The findings are discussed in relation to different socioeconomic and hygienic backgrounds of the children.

Trichophyton eboreum sp. nov. isolated from human skin

An unusual dermatophyte was isolated from the plantar scales of a human immunodeficiency virus-positive man with tinea pedis. Morphology, physiology, and molecular data provided evidence to support the new species Trichophyton eboreum. This dermatophyte is characterized by rapid growth on common mycological media, a flat powdery off-white colony, formation of clavate microconidia, smooth- and thin-walled cylindrical or club-shaped macroconidia with two to nine cells, the presence of hook-shaped hyphae, the production of cleistothecium-like structures and spiral hyphae in older cultures, positive hair perforation, the absence of pigmentation on potato glucose agar, the absence of a requirement for vitamins, a weak positive urease reaction, no growth at 37 degrees C, resistance to 5% NaCl, resistance to fluconazole, good growth on human epidermal keratin, and the production of various enzymes on different media by the API-ZYM test. More than 5% divergence from any known species of dermatophyte was revealed by sequence analysis of the internal transcribed spacer of the rRNA gene.

White variants of Trichophyton violaceum isolated in Ethiopia

Certain dermatophytes are geographically restricted and endemic in particular parts of the world, while other species may have a sporadic but worldwide distribution. Trichophyton violaceum is one of the most common dermatophytes causing tinea capitis, and is the predominant cause of tinea in Africa, South America and the Indian subcontinent. Among 1187 dermatophyte isolates collected from Ethiopian patients with various types of tinea, 32 isolates had uncharacteristic phenotypic features. Based on conventional methods complemented by sequence analysis of the rDNA ITS2 region, these isolates were identified as white variants of T. violaceum. This is the first time that white isolates of T. violaceum have been identified in Ethiopia.

Superficial mycoses due to Trichophyton violaceum in Athens, Greece: a 15-year retrospective study

This is a retrospective study on the superficial mycoses due to Trichophyton violaceum in the greater Athens area for the last 15 years - 1989-2003. During this period 104 patients were found to have an infection due to T. violaceum- an incidence rate of 0.75% of all dermatophytosis. Of the patients 59 were Greeks, 15 Greek Gypsies and 30 immigrants mostly from Albania (50%). Of them 58 were children, 46 adults (mainly women, 34 cases). Trichophyton violaceum infection was presented with a variety of manifestations (127 cases). The prevailing was tinea capitis present in 85 patients - 57 children, 24 women and four men (women : men 6 : 1). Tinea capitis together with other forms of the infection was found in 14 patients. Tinea facie, corporis, manuum, barbae and unguium were seen in nineteen patients. The isolation rate of T. violaceum infection in the Greek population remained at a low level for three decades after the mid-1960s. However, a substantial increase in the isolation rate is observed in the mid-1990s attributed mainly to the influx of economic immigrants from countries where the infection is endemic.

Majocchi's granuloma of the vulva caused by Trichophyton mentagrophytes

We report a case of Majocchi's granuloma caused by Trichophyton mentagrophytes on the vulva in a 23-year-old girl who had used topical steroids for many years. Her dog was a source of the infection.

Onychomycosis in Ceará (Northeast Brazil): epidemiological and laboratory aspects

Knowledge of epidemiological and mycological characteristics of onychomycosis has been noted by many authors as being an important tool for control of these fungal infections. This study seeks to improve knowledge of onychomycosis epidemiology and mycological features. Samples were taken from infected fingernails and toenails of 976 patients undergoing treatment at a respected Dermatology Center in Ceará, Fortaleza, CE, Brazil. Specimens from 512 patients (52%) were positive for onychomycosis. From the culture-positive samples, yeasts of the genus Candida (C. albicans, C. tropicalis, C. krusei, C. parapsilosis) were dominant. The dermatophytes isolated (Trichophyton rubrum, T. tonsurans, T. mentagrophytes var. mentagrophytes) were dominant in 46 patients (12.99%). The mould Fusarium spp. was isolated from 29 patients (8.19%). Yeast of the genus Candida is the main causal factor in onychomycosis in our region. Also, the study showed the importance of performing direct examination and culture in diagnosis of onychomycosis.

Dermatophytes growth curve and in vitro susceptibility test: a broth micro-titration method

The introduction of systemic antifungal drugs which act upon different targets is the main issue of the in vivo antifungal resistance control. Different factors, such as growth curve phase, quality of the specimen, quantity of the inoculum, temperature, pH, culture medium composition, incubation duration and solvent, are believed important factors affecting minimum inhibitory concentration (MIC) value to most of the antifungal agents. We assayed an in vitro susceptibility test with 40 isolates of dermatophytes: Microsporum canis, Trichophyton rubrum, Trichophyton mentagrophytes and Epidermophyton floccosum against griseofulvin, fluconazole, itraconazole and terbinafine, using the guidelines of the M38-P document approved by the NCCLS. We determined the growth curves, to estimate the specific growth rate (mu max) and the generation time (G) of each dermatophyte, using dry weight and spectrophotometry methods. We demonstrate that, at 192 h, all fungi tested had a constant growth curve and we considered this as the optimal time for MIC determination. Terbinafine, griseofulvin and itraconazole possessed the highest antifungal activity against the four groups of dermatophytes studied. Fluconazole demonstrated no efficacy. Our MIC results differ from other authors and this difference is due to the timing of the MIC determination based on the growth curve of each fungi tested.

Prevalence of Dermatophytic Fungal Infections in Children: A Recent Study in Anambra State, Nigeria

We conducted a recent survey of dermatological fungal infections amongst children in both urban and rural parts of Anambra State in the south-east geographical flank of Nigeria during the period January 2003 to December 2003. Samples were collected from 1624 children with clinically suggestive lesions and also between the ages of 4 and 16. Young children aged 7-11 and 4- 6 years had significantly higher incidences (P < 0.05) than their older colleagues aged 12-16 years among samples proved to be mycologically positive by microscopy, culture or both. There was a significant difference in the incidence of dermatophytoses amongst children in urban and rural areas investigated (P < 0.05). Tinea capitis was the predominant clinical type. Trichophyton tonsurans was the most prevalent etiological agent while Microsporum audouinii was the least in occurrence. We compared our result with a recent study in the northern geographical zone and observed that although incidence of dermatophytoses is higher in northern Nigeria, tinea capitis was the predominant clinical type in both regions. In addition, the etiological agents appear to vary from time to time in their occurrence and the reasons for these observations are discussed. A regular surveillance and assessment of the etiologic agent and its prevalence by medical mycologists is strongly recommended to facilitate monitoring, reduce/prevent transmission and spread of dermatophytes in countries like Nigeria where they constitute a public health problem.

First report on autochthonous urease-positive Trichophyton rubrum (T. raubitschekii) from South-east Europe

BACKGROUND

Trichophyton raubitschekii is a dermatophyte belonging to the T. rubrum complex and is differentiated principally by its positive urease activity and production of profuse macroconidia and microconidia in culture. It is classically isolated from African, South-east Asian and Australian aboriginal patients with tinea corporis or tinea cruris.

OBJECTIVES

This study was undertaken to screen Greek and Bulgarian clinical isolates identified as T. rubrum for T. raubitschekii and to delineate these strains by two molecular methods used for the first time in T. rubrum epidemiological studies.

METHODS

Ninety-five Greek and 10 Bulgarian strains, originating from various body sites, initially identified as T. rubrum, were screened for urease activity. The biochemical properties and morphology of the urease-positive strains were determined. Strains were delineated with polymerase chain reaction (PCR)-ribotyping amplifying repeat elements of the intergenic spacer region and by PCR fingerprinting.

RESULTS

Five Greek and one Bulgarian T. raubitschekii strains were identified comprising isolates from patients with tinea manuum (one), tinea corporis (one), tinea cruris (one) and tinea unguium (three). Only one strain had the classical T. raubitschekii microscopic morphology, whereas the remaining five presented a dominant arthroconidial phenotype. Both typing methods clustered all T. raubitschekii and T. rubrum isolates together in the same group, indicating strain homogeneity in the genetic regions examined.

CONCLUSIONS

The reported isolation of T. raubitschekii in the Balkan and South-eastern Mediterranean regions extends the geographical distribution of this species. As the more primitive T. raubitschekii probably represents the parental population of T. rubrum, the Greek and Bulgarian T. raubitschekii strains could represent a remnant of the T. rubrum spread that took place after the First World War, rather than being a recent epidemiological event.

Die Variante Raubitschekii von Trichophyton rubrum hat Deutschland erreicht

This is the second report on an isolation of the variety raubitschekii of Trichophyton (T.) rubrum in Germany. The patient was a young man born in Cameroon who presented with an extensive tinea corporis et manuum. The variety raubitschekii can be distinguished from similar looking dermatophytes by its brownish color, by the formation of abundant T. rubrum-like macroconidia, by the production of urease, by a negative hair perforation test, and by DNA analysis. In addition, further characteristics of this variety were determined. So far, the variety raubitschekii has been primarily found as a cause of tinea corporis in patients from Asia or Africa. In the future, it should be considered as a potential pathogen in Germany as well.

Prevalence of tinea capitis in Ethiopian schoolchildren

The prevalence of dermatophytosis and the spectrum of dermatophyte species were determined in children attending two schools in Addis Ababa, Ethiopia. Demographic and clinico-dermatological data were collected. Specimens were taken for microscopy and culture from all suspected lesions. Dermatophyte species were identified by morphology and biochemical tests, supplemented by sequencing of the rDNA ITS 2 region in selected isolates. From the Biruh Tesfa Elementary School (BTES) 824 students, and from Mount Olive Academy (MOA) all 124 students, were included. In BTES 513 (62.3%) students were clinically diagnosed with dermatophytosis, 463 (90.3 %) of them with tinea capitis. In 200 consecutive samples from BTES, and in 66 from MOA, 75 and 62%, respectively, contained fungal elements at microscopy. From BTES, 163/496 (33%) samples were culture-positive, of which 149 (91.4%) grew with dark purple colonies identified as Trichophyton violaceum, while 244 (49.4%) samples were contaminated. A few strains grew slowly developing white to cream colonies, two were identified as T. verrucosum, and 12 as white T. violaceum. From MOA 44 (66.7%) of samples were culture-positive, 38 (87%) were identified as T. violaceum, and one (2.3%) as T. verrucosum, while 33% showed no growth. Four white isolates of T.violaceum were confirmed by DNA-sequencing. Dermatophytosis was thus diagnosed in 55-62% of children screened at two schools of different socioeconomic standards in the Ethiopian capital. Trichophyton violaceum constituted 87-90% of all isolates. White variants of T. violaceum were diagnosed in 16 cases.

Mycological examinations on the fungal flora of the chicken comb

A total of 500 combs of adult chickens from two different locations in Germany (Hessen and Schleswig-Holstein) were clinically and mycologically examined. The chickens came from three battery cages (n = 79), one voliere system (n=32), six flocks maintained on deep litter (n = 69) and 12 flocks kept on free outdoor range (n=320). Twenty-two of the 500 chicken combs (4.4%) were found to have clinical signs: only non-specific lesions neither typical of mycosis nor of avian pox such as desquamation with crust formation, yellow to brown or black dyschromic changes, alopecia in the surrounding area and moist inflammation. Only seven of the 22 clinically altered combs showed a positive mycological result; the non-pathogenic and geophilic Trichophyton terrestre in one case and non-pathogenic yeast in six cases. The following fungi were seen in the different housing systems: 13 dermatophytes (2.6% of 500 samples): 12 x T. terrestre, 1 x Trichophyton mentagrophytes, 11 isolates of Chrysosporium georgiae (2.2% of 500 samples) and 149 isolates of yeasts (29.8%): Malassezia sympodialis: n = 52, Kloeckera apiculata: n = 33, Trichosporon capitatum (syn. Geotrichum capitatum): n = 23, Trichosporon cutaneum/Trichosporon mucoides: n = 12, Trichosporon inkin (syn. Sarcinosporon inkin): n = 8 and Candida spp.: n = 21, including pathogenic or possibly pathogenic species: Candida albicans: n = 3, Candida famata: n = 4, Candida guilliermondii: n = 3, Candida lipolytica: n = 3, Candida dattila: n = 2 and one isolate each of Candida glabrata, Candida parapsilosis, Candida aaseri, Candida catenulata sive brumpti, Candida fructus and Candida kefyr sive pseudotropicalis. There is no stringent correlation between the clinical symptoms diagnosed on the chicken combs and the species of yeasts isolated. The causative agent of favus in chickens, Trichophyton gallinae, and the saprophytic yeast in pigeons, Cr. neoformans were not isolated. The most frequently isolated yeasts M. sympodialis and Kloeckera apiculata are suggested to be classified as members of the resident flora of the chicken comb.

Prevalence of tinea capitis and tinea pedis in Barcelona schoolchildren

BACKGROUND

Although dermatophytoses can appear at any age, some types are particularly prevalent in children. There are no prior data on the prevalence of tinea capitis and tinea pedis in Barcelona, Spain. To identify the prevalence of tinea in school children in the area with the highest immigrant population in this city, a cross-sectional study was performed. A second objective was to identify the etiologic agent to study the possibility of the introduction of foreign dermatophyte species and to evaluate the possibility of encountering healthy hosts.

METHODS

From October 2002 until June 2003, we evaluated 1305 schoolchildren, ages 3-15 years, belonging to 21 schools located in the inner city of Barcelona to determine the prevalence of tinea capitis and pedis in school children. Cultures of scalp and feet were done in each child.

RESULTS

36(2.8%) children had tinea pedis and 3 (0.23%) had tinea capitis. One child had tinea capitis and tinea pedis, caused by different species (t. capitis caused by Trichophyton mentagrophytes and tinea pedis caused by Trichophyton rubrum). Of the 39 positive cases for dermatophytes, the etiologic agent in 18 (46.1%) was T. mentagrophytes, 17 (43.5%) T. rubrum, 2 (5.5%) Epidermophyton floccosum and 2 (5.5%) Trichophyton tonsurans. Of these 39 cases of tinea, 15 (38.5%) were Spanish natives and 22 (56.4%) were immigrants.

CONCLUSION

The prevalence of tinea capitis was lower that we had expected, and it was noted that there was a greater prevalence of tinea pedis among schoolchildren 13-15 years of age (64.10%), the great majority of them male. The number of cases of tinea was significantly greater in immigrants.

Strain differentiation of Trichophyton rubrum by random amplification of polymorphic DNA (RAPD)

Trichophyton rubrum is an important cause of dermatomycoses. Molecular strain typing methods have recently been developed to address questions about epidemiology and source of relapse following treatment. This report describes the application of RAPD for molecular strain differentiation of this fungus utilizing the primers 1- (5'-d[GGTGCGGGAA]-3') and 6- (5'-d[CCCGTCAGCA]-3'). A total of five RAPD patterns were observed among 10 strains of T. rubrum, with each of the primers used. We conclude that RAPD analysis using primers 1 and 6 can be used in epidemiological studies.

Dermatophytosis in Tulugudu Island, Ethiopia

The objective of this investigation was to assess the prevalence of dermatophytoses in children in a geographically restricted area in the Ethiopian countryside, and to determine the aetiological agents of these infections. Demographical and clinical-dermatological data were collected from all children 4-15 years of age on Tulugudu Island, Southern Ethiopia. Mycological specimens were taken and species identification determined through morphological observations and biochemical tests, complemented with sequencing of rDNA ITS2 region when necessary. Of 171 children, 96% shared combs, 85% shared beds and 97% had animal contact. Family size was > 5 persons in 50% of the test subjects and prevalence of tinea capitis was elevated in this group (P < 0.005). Dermatophytoses were clinically diagnosed in 136 cases (79.5%). Tinea capitis (T. capitis) was the most common manifestation with 104 cases (76.5%). T. capitis was combined with dermatophytic infections at other sites in 19 cases. Tinea faciae and Tinea corporis were found in four and two cases, respectively, and pediculosis capitis was diagnosed in 2.9% of the test subjects. Of 135 samples from hair (n = 112), skin (n = 19) and finger-nail (n = 4), 74.1% were microscopy-positive for dermatophytes, 73% were positive in culture, giving an overall prevalence of dermatophytoses in 57.3% of all children examined. Trichophyton violaceum was identified in 80.6% of cultures, Trichophyton verrucosum in 16.3% and Trichophyton tonsurans in 2.0%. One isolate was identified as a white variant of T. violaceum. Tinea capitis was highly prevalent in children on Tulugudu Island, Southern Ethiopia. The anthropophilic species T. violaceum dominated as an aetiological agent. Zoophilic dermatophytes were relatively rarely isolated from clinical specimens, despite the children's frequent contact with animals.

Origins of microsatellite diversity in the Trichophyton rubrum-T. violaceum clade (Dermatophytes)

We analyzed the population structure of the anthropophilic dermatophyte species Trichophyton violaceum, which mainly causes tinea capitis, and T. rubrum, the most frequently isolated agent of dermatophytosis worldwide. A microsatellite marker (T1) was developed by using the enrichment technique for microsatellites. The T1 marker containing a (GT)(8-10) repeat was proven to specifically amplify both species, underlining their close kinship. Four polymorphic alleles were detected within a set of about 130 strains by using polyacrylamide gel electrophoresis with this marker. An association with geographic origin of the isolates was apparent. Given the close relatedness of both species, these data suggest an African origin of the entire T. rubrum complex, followed by the emergence of a new genotype (B) in Asia with subsequent spread of this genotype over Europe and the United States.

Multiplication of an ancestral gene encoding secreted fungalysin preceded species differentiation in the dermatophytes Trichophyton and Microsporum

Dermatophytes are human and animal pathogenic fungi which cause cutaneous infections and grow exclusively in the stratum corneum, nails and hair. In a culture medium containing soy proteins as sole nitrogen source a substantial proteolytic activity was secreted by Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum canis. This proteolytic activity was 55-75 % inhibited by o-phenanthroline, attesting that metalloproteases were secreted by all three species. Using a consensus probe constructed on previously characterized genes encoding metalloproteases (MEP) of the M36 fungalysin family in Aspergillus fumigatus, Aspergillus oryzae and M. canis, a five-member MEP family was isolated from genomic libraries of T. rubrum, T. mentagrophytes and M. canis. A phylogenetic analysis of genomic and protein sequences revealed a robust tree consisting of five main clades, each of them including a MEP sequence type from each dermatophyte species. Each MEP type was remarkably conserved across species (72-97 % amino acid sequence identity). The tree topology clearly indicated that the multiplication of MEP genes in dermatophytes occurred prior to species divergence. In culture medium containing soy proteins as a sole nitrogen source secreted Meps accounted for 19-36 % of total secreted protein extracts; characterization of protein bands by proteolysis and mass spectrometry revealed that the three dermatophyte species secreted two Meps (Mep3 and Mep4) encoded by orthologous genes.

Genetic Heterogeneity in the rRNA Gene Locus of Trichophyton tonsurans

Trichophyton tonsurans is the major pediatric pathogen in tinea capitis, causing disparate disease presentations. Little is known about genetic variation, which may ultimately be linked to divergent disease status. This investigation was aimed at identifying genetic variants of T. tonsurans by methods that can facilitate strain discrimination in population-based studies. Ninety-two isolates were acquired from six U.S. microbiology laboratories, and genomic DNA was isolated from mature colonies. The nontranscribed spacer (NTS) was amplified by PCR, and products from isolates with various amplicon sizes were fully sequenced. Nested amplification, targeting a variable internal repeat (VIR) region, allowed assignment of variant type by fragment size. Subvariant type was assigned by a combination of PCR-restriction fragment length polymorphism-based assays. Five variants differing in size (348 to 700 bp) and sequence were identified within the VIR region comprised of several large repeats (104, 140, and 194 bp) arranged in tandem. Seven single-nucleotide polymorphisms (SNPs) were detected across the NTS, with five occurring in the constant regions flanking the VIR region and two occurring in the VIR region. Additionally, a 10-bp insertion and a 14-bp deletion were identified upstream of the VIR region. The combination of SNPs revealed seven haplotype patterns which were stable upon serial passage over 1 year. No sequence variations were identified within the internal transcribed spacer regions. Unique NTS sequences were utilized to develop a duplex PCR assay that discriminated T. tonsurans from other dermatophytes. Of the 92 isolates evaluated, this genotyping scheme distinguished 12 distinct strains, providing evidence of genetic heterogeneity in T. tonsurans.