Variation in Restriction Fragment Length Polymorphisms among Serial Isolates from Patients with
            <i>Trichophyton rubrum</i>
            Infection

Gupta, Aditya K.; Kohli, Yatika; Summerbell, Richard C.

doi:10.1128/jcm.39.9.3260-3266.2001

Cited by 36 publications

(37 citation statements)

References 36 publications

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“…The T1 microsatellite developed in our study is the second DNA marker displaying polymorphisms among strains that are otherwise genetically homogenous. Using the TRS marker, a repeat region within the NTS region of the rDNA, several authors were also able to detect variability among isolates of this species (7,6,15). However, no clear association was found with the clinical picture or the geographic origin.…”

Section: Discussionmentioning

confidence: 96%

Origins of Microsatellite Diversity in the Trichophyton rubrum - T. violaceum Clade (Dermatophytes)

et al. 2004

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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.Despite large phenetic differences, Trichophyton rubrum and T. violaceum are closely related dermatophytes, composing a single, robust clade in ribosomal DNA (rDNA) internal transcribed spacer (ITS) phylogeny (5). T. rubrum is remarkable because its molecular variability is minimal. Some polymorphisms among clinical isolates have been detected in the copy number of a repetitive element (TRS) in the nontranscribed spacer (NTS) of the ribosomal operon (7), but no clear correlation with either clinical picture or geographic origin was apparent. Detection of additional markers therefore remains necessary.Trichophyton rubrum mostly causes mild tinea pedis and onychomycosis. Its transmission from human to human has particularly been promoted by the general use of closed footwear in urban populations. Gräser et al. (3), by using PCR fingerprinting, amplified fragment length polymorphism, and anonymous DNA markers, proved that T. rubrum evolved only very recently, possibly from a single clone. A detectable degree of polymorphism, combined with the rapid transmission from human to human, would enable the localization of the origin of this species before it emerged on a worldwide scale. In older literature (14) the species has been hypothesized to originate from the Far East and subsequently to have been spread by soldiers during the First World War.In contrast, the T. violaceum complex seems to have gone through speciation processes in Africa and the Middle East. The species comprises some variants or sister species which all mainly cause inflammatory tinea capitis or tinea corporis but differ slightly in cultural characteristics and production of extracellular metabolites: T. gourvilii, T. soudanense, and T. yaoundei. These taxa were reduced to synonymy of T. violaceum on the basis of ITS sequence data (5), but this unification conceals possible evolutionary diversification. Microsatellite markers developed for the model species T. rubrum are likely to produce polymorphisms in the entire T. rubrum clade that includes T. violaceum. This provides significant possibilities for diagnostic and epidemiological typing studies.The aim of the present stud...

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Section: Discussionmentioning

confidence: 96%

Origins of Microsatellite Diversity in the Trichophyton rubrum - T. violaceum Clade (Dermatophytes)

et al. 2004

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“…Given the failure of some of the aforementioned techniques to distinguish T. tonsurans strains (9,10,14,16) and the paucity of sequence information for the species, the rDNA gene locus was selected for this investigation because the flanking 25S, 18S, and 5.8S rDNA sequences are highly conserved among species. In order to unequivocally determine the nature of this locus in T. tonsurans, multiple strains (n ϭ 20), including all those exhibiting length variation in an initial long PCR of the NTS region, were entirely sequenced.…”

Section: Discussionmentioning

confidence: 99%

Genetic Heterogeneity in the rRNA Gene Locus of Trichophyton tonsurans

Gaedigk

Abdel‐Rahman

2003

J Clin Microbiol

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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 polymorphismbased 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.Cutaneous infections caused by the dermatophyte species remain pervasive in every age group worldwide. Millions of individuals are affected by these pathogens, which contribute to health care costs in excess of $400 million a year for treatment alone (4,20). In fact, the impact of dermatophyte infections on human disease is so clearly established that a recent white paper by the fungal research community identified Trichophyton rubrum as one of five medically relevant pathogens targeted as initial sequencing candidates by the Fungal Genome Project (2). While T. rubrum is the primary agent of dermatomycoses in adults, Trichophyton tonsurans remains the principal etiologic agent of tinea capitis in the United States and is on the rise in regions of Europe and Japan (5,16,19).Disparate clinical presentations of T. tonsurans tinea capitis are well recognized, with infection spanning the spectrum from an asymptomatic carrier state to a chronic noninflammatory state and a severe acute inflammatory state. While it is likely that interindividual variabilities in both host and fungus work in concert to create these differences, the primary elements that dictate the course of the disease remain to be elucidated. We have recently determined that a significant degree of int...

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“…Several investigations targeting the rRNA locus report the presence of only one strain contributing to infections of the feet and toenails (10,16). In one study, serial isolates were described as switching back and forth between two strain types, but in no sample did the strains occur together (10). In contrast, a single study reported that 60% of onychomycosis specimens were comprised of multiple strains (21).…”

Section: Discussionmentioning

confidence: 95%

“…Yet multistrain infections are infrequently reported in clinical investigations that have evaluated dermatophytes at the molecular level. Several investigations targeting the rRNA locus report the presence of only one strain contributing to infections of the feet and toenails (10,16). In one study, serial isolates were described as switching back and forth between two strain types, but in no sample did the strains occur together (10).…”

Section: Discussionmentioning

confidence: 99%

“…Without the ability to reliably discriminate variants within a species one cannot adequately determine the extent of genetic variation within and between pathogen populations, investigate the origins of phenetic diversity within a species, or gain insight into the relationship between the organism and its host (17). For many fungal pathogens, strain-typing methods have been developed for neutrally evolving areas of the genome, with typing strategies aimed at detecting intraspecific genetic variation in the dermatophytes almost exclusively represented by the ribosomal DNA (rDNA) locus (9,10,11,16,18,21).…”

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Multilocus Genotyping Identifies Infections by Multiple Strains of Trichophyton tonsurans

2007

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Acquisition of multiple genetic strains of a single dermatophyte species should not be unexpected in areas of high endemicity, and yet multistrain infections are infrequently reported. This communication details mixed Trichophyton tonsurans infections and highlights the need to confirm the presence of multiple strains in a clinical single isolate by use of a multilocus approach.Clinical and epidemiological investigations, along with population-based evolutionary studies, all benefit from the ability to distinguish pathogen strains. Without the ability to reliably discriminate variants within a species one cannot adequately determine the extent of genetic variation within and between pathogen populations, investigate the origins of phenetic diversity within a species, or gain insight into the relationship between the organism and its host (17). For many fungal pathogens, strain-typing methods have been developed for neutrally evolving areas of the genome, with typing strategies aimed at detecting intraspecific genetic variation in the dermatophytes almost exclusively represented by the ribosomal DNA (rDNA) locus (9,10,11,16,18,21).The rDNA region remains popular for investigations of microbial pathogens. The intergenic spacer is known to exhibit a large degree of variation, and the highly conserved flanking rDNA genes make it relatively easy to target the region. Nevertheless, it is not uncommon for papers describing straintyping methods using this region to report amplification patterns that are difficult to interpret (11,12). We similarly reported challenges with initial attempts at characterizing this region from Trichophyton tonsurans. However, careful optimization of the PCR amplification procedures ensured a singular, discernible pattern for each strain in the validation set (9). Yet subsequent application of our PCR-restriction fragment length polymorphism (PCR-RFLP)-based strain-typing methods to a large-scale epidemiologic investigation revealed composite RFLP patterns at this locus (2). Notably, examining coding region variations in conjunction with variations in the rDNA locus offered evidence that these patterns were consistent with infections comprised of more than one strain.Given that clinically derived samples and samples acquired in large-scale studies are rarely plated in a clonal fashion, typing strategies require the ability to discriminate mixed infections (i.e., infections by more than one strain). This is particularly relevant when studies are conducted in areas of high endemicity where more than half of the relevant sample population may be harboring the pathogen and multiple strain types are known to occur. This communication provides details on multistrain T. tonsurans infections confirmed from a single clinical isolate by use of a multilocus approach. MATERIALS AND METHODSClinical isolates. The T. tonsurans isolates described for this investigation were obtained from a prospective epidemiologic investigation reported on previously by the investigators (2). Scalp cultures were performed ...

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Variation in Restriction Fragment Length Polymorphisms among Serial Isolates from Patients with Trichophyton rubrum Infection

Cited by 36 publications

References 36 publications

Origins of Microsatellite Diversity in the Trichophyton rubrum - T. violaceum Clade (Dermatophytes)

Origins of Microsatellite Diversity in the Trichophyton rubrum - T. violaceum Clade (Dermatophytes)

Genetic Heterogeneity in the rRNA Gene Locus of Trichophyton tonsurans

Multilocus Genotyping Identifies Infections by Multiple Strains of Trichophyton tonsurans

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