[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.

Phylogenetic analysis of Trichophyton mentagrophytes human and animal isolates based on MnSOD and ITS sequence comparison

Dermatophytes are keratinophilic fungi able to infect keratinized tissues of human or animal origin. Among them, Trichophyton mentagrophytes is known to be a species complex composed of several species or variants, which occur in both human and animals. Since the T. mentagrophytes complex includes both anthropophilic and zoophilic pathogens, accurate molecular identification is a critical issue for comprehensive understanding of the clinical and epidemiological implications of the genetic heterogeneity of this complex. Here, 41 T. mentagrophytes isolates from either human patients (14 isolates) or animals (27 isolates) with dermatophytosis were prospectively isolated by culture and identified on morphological bases at the University Hospital Centres of Lille and Poitiers, and the Veterinary School of Alfort, respectively. The isolates were differentiated by DNA sequencing of the variable internal transcribed spacer (ITS) regions flanking the 5.8S rDNA, and of the housekeeping gene encoding the manganese-containing superoxide dismutase (MnSOD), an enzyme which is involved in defence against oxidative stress and has previously provided interesting insight into both fungal taxonomy and phylogeny. ITS1-ITS2 regions and MnSOD sequences successfully differentiate between members of the T. mentagrophytes complex and the related species Trichophyton rubrum. Whatever the phylogenetic marker used, members of this complex were classified into two major clades exhibiting a similar topology, with a higher variability when the ITS marker was used. Relationships between ITS/MnSOD sequences and host origin, clinical pattern and phenotypic characteristics (macroscopic and microscopic morphologies) were analysed.

Widespread tinea corporis caused by Trichophyton rubrum with non-typical cultural characteristics--diagnosis via PCR

From the epidemiological point of view, Trichophyton rubrum is the most important dermatophyte in the Western world. Mostly, the lesions of fungal infections of the skin are restricted and circumscribed. Immunodeficiency, diabetes or treatment with steroids, however, favour widespread disease involving the entire integument. In the present study, we describe a patient without immunodeficiency or diabetes presenting with widespread tinea corporis caused by T. rubrum. The fungal isolate showed atypical morphological features. Moreover, the typical metabolic features (negative urease test, production of red pigment on potato dextrose agar) were expressed with delay after 6 weeks of cultivation. Thus, sequencing of the internal transcribed spacer of the ribosomal DNA was applied to identify the fungal isolate and led us to the correct diagnosis, before conventional mycological methods were successful.

cDNA representational difference analysis used in the identification of genes expressed by Trichophyton rubrum during contact with keratin

Dermatophytes are adapted to infect skin, hair and nails by their ability to utilize keratin as a nutrient source. Trichophyton rubrum is an anthropophilic fungus, causing up to 90% of chronic cases of dermatophytosis. The understanding of the complex interactions between the fungus and its host should include the identification of genes expressed during infection. To identify the genes involved in the infection process, representational difference analysis (RDA) was applied to two cDNA populations from T. rubrum, one transcribed from the RNA of fungus cultured in the presence of keratin and the other from RNA generated during fungal growth in minimal medium. The analysis identified differentially expressed transcripts. Genes related to signal transduction, membrane protein, oxidative stress response, and some putative virulence factors were up-regulated during the contact of the fungus with keratin. The expression patterns of these genes were also verified by real-time PCR, in conidia of T. rubrum infecting primarily cultured human keratinocytes in vitro, revealing their potential role in the infective process. A better understanding of this interaction will contribute significantly to our knowledge of the process of dermatophyte infection.

Var. raubitschekii of Trichophyton rubrum as a cause of tinea in Germany

Trichophyton raubitschekii was originally described as a distinct dermatophyte species but is now classified as a variant of Trichophyton rubrum. The variant raubitschekii differs from common strains of T. rubrum with regard to morphology, physiology, epidemiology and patterns of infection. It is mostly found in Africa, Asia and South America, but the literature and our observations reveal that seven patients (four men, three women) with T. rubrum var. raubitschekii-infections were meanwhile seen in Germany. All of them were born in Africa and they suffered from tinea corporis or tinea pedum, but onychomycosis was seen as well. All strains matched the typical characteristics of the variant raubitschekii except that one strain had a minimal capacity to perforate hair. Until now, the strains of T. rubrum var. raubitschekii isolated in Germany were probably imported by migration of the patients and so far no further spreading within Germany was observed. However, such a spreading is likely to occur in the future and therefore a monitoring is needed. This can be achieved only when the variant raubitschekii is looked for in the laboratories and is reported with its full name.

In vitro antifungal susceptibility patterns of dermatophyte strains causing tinea unguium

BACKGROUND

Dermatophytes are the major responsible organisms in onychomycosis. Although recent antifungal agents have high success rates in treating this condition, lack of clinical response may occur in 20%. Antifungal drug resistance may be one of the causes of treatment failure. The need for in vitro antifungal drug resistance in daily practice is still under discussion.

OBJECTIVE

We aimed to determine the in vitro susceptibility patterns of dermatophytes causing onychomycosis, against the traditionally available systemic antifungal agents terbinafine, itraconazole and fluconazole.

METHODS

In total, 100 otherwise healthy patients with suspected onychomycosis were included. Nail clippings were cultured on Sabouraud dexrose agar, mycobiotic agar and dermatophyte test medium. Antifungal susceptibility tests were carried out, mainly following The National Committee for Clinical and Laboratory Standards (M38-P) protocol standard for filamentous fungi. Different concentrations of terbinafine (0.008-8 microg/mL), itraconazole (0.015-16 microg/mL) and fluconazole (0.06-64 microg/mL) were tested. Minimum inhibitory concentration end-point determination was chosen as 100% growth inhibition for terbinafine and 80% for azoles.

RESULTS

Of the 100 nail samples, 43% grew dermatophytes. The main causative organism was Trichophyton rubrum (91%) followed by Trichophyton mentagrophytes (9%). Terbinafine had the lowest minimum inhibitory concentration (0.008 microg/mL) followed by itraconazole. Fluconazole showed the greatest variation in minimum inhibitory concentration (0.03-2 microg/mL) and had different susceptibility patterns for the two species.

CONCLUSIONS

Of the three antifungals tested, terbinafine had the most potent in vitro antifungal activity against dermatophytes. Antifungal susceptibility tests would be useful to screen antifungal-resistant dermatophyte strains.

Fast and sensitive detection of Trichophyton rubrum DNA from the nail samples of patients with onychomycosis by a double-round polymerase chain reaction-based assay

BACKGROUND

Trichophyton rubrum is one of the most frequently isolated pathogens in onychomycosis. Isolation of T. rubrum from nail samples by traditional methods is time-consuming and has a high false-negative rate of detection.

OBJECTIVES

To investigate the detection of T. rubrum in nail samples using DNA detection methods.

METHODS

A total of 62 nail samples from onychomycosis patients with T. rubrum infection were evaluated by culture on Sabouraud's dextrose agar plus chloramphenicol, cycloheximide and gentamicin and compared with genotyping methods utilizing DNA extracted directly from nails. Trichophyton rubrum DNA isolated directly from nails was amplified using two different conserved regions [actin gene and internal transcribed spacer 1 (ITS)] in double-round polymerase chain reaction (PCR) assays.

RESULTS

Forty-eight of 62 (77.4%) samples were potassium hydroxide (KOH) positive, but T. rubrum culture was positive in only 14 of 62 (22.6%) samples. By contrast, direct T. rubrum DNA detection rate was 59.7% (37/62) by actin gene and 45.2% (28/62) by ITS1 region PCR assays corresponding to higher detection frequencies compared with culture with P < 0.001 and < 0.008, respectively. The combined detection of actin and ITS1 was 69.4% (43/62). Interestingly, T. rubrum DNA was detected in 9 out of 14 (64.3%) of KOH- and culture-negative samples. Importantly, 15 culture-negative samples collected from patients undergoing antifungal treatment tested PCR positive using the actin region.

CONCLUSIONS

These results suggest that a direct DNA detection protocol is more sensitive, accurate and faster than traditional culture-based methods. It can be useful to detect T. rubrum in patients undergoing antifungal therapy and who have been reported mycologically cured on the basis of a culture-based method.

Tinea capitis: ringworm of the scalp

The guideline tinea capitis, as passed by three German medical societies, is presented in the present study.

Genotyping of Trichophyton rubrum by analysis of ribosomal-DNA intergenic spacer regions

An attempt was made to explore the genotyping of Trichophyton rubrum (T. rubrum) and the relationship between genotype and geographical origin using ribosomal restriction endonuclease polymorphic analysis. The total DNA was extracted by cetyltrimethyl ammonium bromide (CTAB). The probe was amplified from part of the 18S, ITSI, 5.8S, and ITSII region of T. rubrum standard strain with the universal fungal primers NS5 [5'-AACTT AAAGG AATTG ACGGA AG-3'] and ITS4 [5'-TCCTC CGCTT ATTGA TATGC-3']. The genomic DNA of 49 clinical T. rubrum isolates digested by EcoR1 were hybridized with this probe, and the hybridization patterns were used as the basis of genotyping. Of the data from 49 strains of T. rubrum studied (21 from Nanjing, 26 from Dalian, and two from Beijing), 20 individual patterns (DNA Type A-T) were identified, among which Type A-C accounted for 48.98% of all the strains. The DNA patterns of Nanjing strains were represented by three bands, those of Dalian strains were represented by four bands. The DNA typing of T. rubrum by Southern blotting was highly sensitive and highly distinguishable. The DNA patterns of Nanjing strains were obviously different from those of Dalian strains.

Multilocus genotyping identifies infections by multiple strains of Trichophyton tonsurans

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.

Exacerbated inflammatory reaction to Trichophyton rubrum infection on an HIV-positive patient successfully treated with fluconazole

A 33 year-old HIV-positive Brazilian female patient was diagnosed with a cutaneous inflammatory reaction on her left forearm. The lesion spread rapidly affecting most of her forearm. The clinical diagnosis of tinea corporis (ringworm) was confirmed by wet mount preparations on 20% KOH and by the isolation of Trichophyton rubrum on pure cultures. Treatment with Fluconazole for a period of four weeks successfully cured the infection.

Species distribution and antifungal susceptibilities of dermatophytes during a one year period at a university hospital in Turkey

Dermatophyte infections have been considered to be a major public health problem in many parts of the world. The aim of this study was to determine the causative agents of dermatophytoses and their antifungal susceptibilities in a Turkish University Hospital, west of Turkey. A total of 926 patients suspected to have dermatophytic lesions were examined over a period of 1 year (2001-2002). Samples collected from skin, hair and nails were submitted to direct microscopical examination using KOH and Calcofluor white stain, cultured on Sabouraud dextrose agar and Mycosel agar. The prevalence of dermatophytoses was 7.34% (68/926). Trichophyton rubrum was the most frequent dermatophyte isolated (56%) followed by T. mentagrophytes (38%), T. violaceum (1.5%), T. verrucosum (1.5%), Microsporum canis (1.5%) and Epidermophyton floccosum (1.5%). Tinea pedis (47%) was the most common type of infection, followed by tinea unguium (29%), tinea inguinalis (15%), tinea corporis (7.4%) and tinea capitis (1.6%). Secondary, we have tested 68 strains of dermatophytes against four antifungal agents following mainly the National Committee for Clinical Laboratory Standards M38-P standard for filamentous fungi. In general, all antifungals were shown to be highly effective and itraconazole and naftifine appeared more active than ketoconazole and oxiconazole.

Trichophyton mentagrophytes sive interdigitale? A dermatophyte in the course of time

Originally, the Trichophyton (T.) mentagrophytes complex distinguished between the anthropophilic subspecies T. mentagrophytes var. interdigitale, T. mentagrophytes var. nodulare (synonym T. krajdenii), and T. mentagrophytes var. goetzii and the zoophilic subspecies T. mentagrophytes var. granulosum (rodents), T. mentagrophytes var. erinacei (hedgehog), and T. mentagrophytes var. quinckeanum (mice). In addition, two sexual species (teleomorph) of this complex are known. These are Arthroderma (A.) benhamiae Ajello and Cheng 1967 and Arthroderma vanbreuseghemii Takashio 1973. According to recent molecular studies,the species T.mentagrophytes is synonymous with only the zoophilic subspecies T.mentagrophytes var. quinckeanum which is rare in Western Europe. The anthropophilic subspecies of T. mentagrophytes, as well as many of the zoophilic strains, formerly differentiated as var. mentagrophytes or var. granulosum, are indistinguishable and are now designated T.interdigitale. The morphological differentiation between anthropophilic and zoophilic T. interdigitale strains by classical microscopical and biochemical methods is often problematic. In particular, it is impossible to differentiate between the zoophilic strains of T. interdigitale, T. mentagrophytes, and the Trichophyton anamorph of A. benhamiae. In these cases, molecular identification methods may be applied to answer epidemiological, taxonomical and therapeutic questions.

Molecular typing and antifungal susceptibility of Trichophyton rubrum isolates from patients with onychomycosis pre- and post-treatment

Forty sequential isolates of Trichophyton rubrum were obtained from patients suffering from onychomycosis at two time points, before and after antifungal oral therapy. Strain differentiation by specific amplification of the two tandemly repeated elements (TRS-1 and TRS-2) of the ribosomal DNA of T. rubrum was performed. In addition, susceptibility tests were executed by the microdilution method with nine antifungal drugs: ketoconazole, itraconazole, fluconazole, miconazole, clotrimazole, isoconazole, griseofulvin, cyclopiroxolamine and terbinafine. The combination of TRS-1 with TRS-2 PCR amplification patterns configured 11 T. rubrum genotypes and the three most prevalent (genotypes 1-I, 5-I and 2-I) accounted for 67.5% of the isolates. Seven isolates (35%) obtained before antifungal oral therapy exhibited genotype 1-I compared to the 11 (55%) obtained after the treatment. Twelve patients exhibited different strains before and after the antifungal therapy. With respect to in vitro susceptibility testing, terbinafine was the most potent agent, followed by itraconazole, clotrimazole, isoconazole, miconazole, cyclopiroxolamine, ketoconazole, griseofulvin and fluconazole. Furthermore, an increase in the minimum inhibitory concentrations (MIC) were observed for most of the azole agents when testing isolates obtained post-treatment from four patients. This increase in MIC occurred concomitantly with the major occurrence of genotype 1-I for isolates obtained after oral therapy. These data attempt to consider the relevance of in vivo drug resistance for onychomycosis caused by T. rubrum.

Growth inhibition of Trichophyton species by Pseudomonas aeruginosa

OBJECTIVE

To assess the ability of Pseudomonas aeruginosa to inhibit the growth of Trichophyton mentagrophytes (TM) and Trichophyton rubrum (TR).

DESIGN

Pseudomonas aeruginosa, Escherichia coli, or Staphylococcus epidermidis were grown in co-culture with either TM or TR.

SETTING

An academic medical center.

MAIN OUTCOME MEASURES

The total fungal units and hyphal-spore ratio were measured at days 1, 5, 10, and 15.

RESULTS

There was a 73% and 46% reduction of total fungal units and a final hyphal-spore ratio of 0.16 and 0.04, respectively, when TM and TR were co-cultured with P aeruginosa. The number of fungal units increased when TM and TR were cultured with E coli (28% and 42%, respectively), S epidermidis (13% and 18%, respectively), and control media (44% and 62%, respectively), and the hyphal-spore ratio increased to above 30 in the presence of S epidermidis, E coli, and control media.

CONCLUSION

Pseudomonas aeruginosa exhibits growth inhibitory properties against TM and TR.

Analysis of the dermatophyte species isolated in the British Isles between 1980 and 2005 and review of worldwide dermatophyte trends over the last three decades

Infections of the skin, hair and nails by dermatophyte fungi are common in developed and developing countries alike. However, the species involved and the resulting clinical entities vary both geographically and with time. We have surveyed 15,333 dermatophytes obtained from primary isolations at the Mycology Reference Laboratory, Bristol, UK from 1980 through 2005. Several striking trends in dermatophyte prevalence were apparent over this period. The relative frequencies of isolations of Microsporum canis (cat and dog ringworm), Trichophyton verrucosum (cattle ringworm), T. mentagrophytes var. mentagrophytes (rodent ringworm) and Epidermophyton floccosum (a cause of human groin and foot infections) all decreased by 90%. Conversely, the contributions of T. tonsurans and T. violaceum (two anthropophilic scalp-infecting species) to total dermatophyte isolations increased by 1000% over the same period. Finally, T. rubrum and T. mentagrophytes var. interdigitale, the two common causes of foot infection comprised 80% of all dermatophytes isolated in 1980 and 90% of isolations in 2005. Similar trends in dermatophyte prevalence were evidenced throughout the British Isles, based on the voluntary reporting of isolations from a large number of British laboratories at 5-yearly intervals over the same period. The implications of these changing patterns of dermatophyte species, and the clinical entities they produce are discussed in the context of a review of worldwide dermatophyte isolations over the last three decades, with emphasis on the causal agents of tinea capitis.

In vitro activity of panomycocin, a novel exo-?-1,3-glucanase isolated from Pichia anomala NCYC 434, against dermatophytes

Killer proteins that are produced and secreted into the environment by certain yeast strains are considered as promising antifungal agents. In this study, in vitro activity of Pichia anomala NCYC 434 (K5) killer protein, panomycocin, which is a 49 kDa glycoprotein with an exo-beta-1,3-glucanase activity was tested against 41 isolates of dermatophytes. Minimum inhibitory concentrations (MICs) were determined by a broth microdilution method based on the reference document M38-A of Clinical and Laboratory Standards Institute (CLSI; formerly NCCLS). For panomycocin MIC determinations two end point criteria MIC-2 (prominent growth inhibition) and MIC-0 (complete growth inhibition) were recorded. All the tested isolates (Microsporum spp. and Trichophyton spp.) were found susceptible to panomycocin. The MIC-2 values ranged from 0.25 to 2 microg ml(-1) and MIC-0 values ranged from 1 to 8 microg ml(-1). These results showed that panomycocin is active in vitro against fungal strains that cause superficial infections and highlighted its probable use as a topical antifungal agent.

Tinea incognito due to Trichophyton mentagrophytes

Tinea incognito is a ringworm infection modified by corticosteroids. We report a case of a 2-year-old girl who developed tinea incognito due to Trichophyton mentagrophytes after applying methylprednisolone aceponate for 3 months. Diagnosis was confirmed by histopathologic and mycological examination, which led to the identification of Trichophyton mentagrophytes var. mentagrophytes, a zoophilic dermatophyte. Previous corticosteroid use in dermatophyte infections can alter their clinical appearance leading to misdiagnosis and delay in appropriate therapy.

ITS barcodes forTrichophyton tonsuransandT. equinum

Early molecular biosystematic studies of dermatophytes created considerable confusion about the taxonomic status of the horse-associated Trichophyton equinum vis-à-vis the anthropophilic T. tonsurans. Though this matter has recently been clarified, routine identification of these species based on the commonly used ribosomal internal transcribed spacer (ITS) sequence has been impractical. This is because, in the available sequences attributed to the species in GenBank, a clear species-level distinction does not appear to exist. In the present study, resequencing the ITS regions of several anomalous isolates is shown to eliminate this problem, which was mainly based on read errors in older sequences. Newly generated sequences and recent GenBank additions are analysed to show that T. equinum appears to be uniform in ITS sequence worldwide, while T. tonsurans is also uniform, excepting a single-base change found in one otherwise typical strain. Analysis also reveals a distinct, as yet incompletely classified Asian genotype that may belong to one or the other of these species. Standard ITS 'barcode sequences' are proposed for T. tonsurans and T. equinum, and a taxonomic neotype is designated to anchor the latter species. T. equinum var. autotrophicum is further evidenced as very closely related to T. equinum var. equinum, and the anomaly of its plesiomorphous phenotype is discussed in a population genetics context.

Isolation of Trichophyton violaceum and Trichophyton soudanense in Baltimore, Maryland

Tinea capitis is of public health importance because of its transmissibility. Trichophyton violaceum and Trichophyton soudanense, which are common causes of tinea capitis in parts of Africa and West Asia, have only rarely been reported to cause dermatophytoses in the United States. We identified 24 patients with 25 positive cultures for T. violaceum or T. soudanense that were processed in a single hospital laboratory in Baltimore, Maryland, between 1 January 2000 and 30 June 2006. Most patients for whom clinical information was available had tinea capitis. There was a marked increase in the isolation of these organisms between the period from 2000 to 2002 and the period from 2003 to 2006, possibly associated with changes in immigration to the Baltimore metropolitan area. The changing epidemiology of this transmissible fungal infection not only is of public health interest as an example of the introduction of a "new" pathogen to an area where it traditionally was not endemic but also is of clinical and microbiological importance given reports suggesting an increasing incidence of tinea capitis in some areas and increasing clinical failure rates of current therapies.

Tracking Trichophyton tonsurans through a large urban child care center: defining infection prevalence and transmission patterns by molecular strain typing

OBJECTIVES

Trichophyton tonsurans is the single most common cause of pediatric dermatophytoses in North America and is observed with increasing frequency in other countries. This investigation was designed to gain insight into the natural course of T. tonsurans infection.

PATIENTS AND METHODS

This 2-year prospective, longitudinal study evaluated all preschool-aged children attending a single child care center. Scalp cultures were collected monthly from each child in attendance, and the presence of disease symptoms recorded at each visit. Dermatophyte genotype was assigned based on the combination of stable sequence variations (2 length variants, 8 single-nucleotide polymorphisms, a 10-base pair insertion, a 14-base pair deletion) present in 2 gene loci.

RESULTS

A total of 3541 scalp cultures were collected from 446 children during 24 months. Twenty-two percent to 51% of scalp cultures per month were positive, contributing 1390 fungal cultures of which 1048 were typeable. Among children with multiple typeable isolates, 51% exclusively carried the same strain, 37% demonstrated a single predominant strain with secondary strains transiently acquired, and 12% harbored a different strain of T. tonsurans with each typeable culture. The probability that the same strain persisted in subsequent months was 0.898 and unlikely to have arisen by chance. Rates of symptomatic disease were significantly different between exclusive, predominant, and transient carriers of T. tonsurans.

CONCLUSIONS

In contrast to dermatophyte infections in older individuals, where symptomatic disease seems to be a consequence of pathogen acquisition and carriers can be traced to an index case, in this preschool-aged population infection was endemic, and symptomatic disease seemed to represent activation of a single strain that persisted on the scalp.

PCR fingerprinting of Trichophyton mentagrophytes var. interdigitale using polymorphic subrepeat loci in the rDNA nontranscribed spacer

The sequence of the nontranscribed spacer (NTS) region of the rDNA of Trichophyton mentagrophytes var. interdigitale strain 2111 was determined, and three individual subrepeat loci identified. The first repeat region contained eight tandem copies of a degenerate 33-43 bp sequence, whilst the second had two complete and two partial 300 bp repeats. The third locus contained six tandemly repetitive elements of between 67 and 89 bp, which showed sequence identity to the TrS2 repeats of Trichophyton rubrum. PCR amplification of the individual repetitive regions from 42 random isolates of T. mentagrophytes var. interdigitale identified fragment length polymorphisms at each locus. Sequence analysis of the PCR products revealed that the size variations resulted from differences in the copy number of each of the three sets of subrepeat elements, TmiS0, TmiS1 and TmiS2. In addition, some indels were present in the flanking regions of the TmiS1 repeats. Combining PCR fingerprints from each of the three polymorphic loci produced a total of 19 individual strain profiles. The method was rapid, reproducible and discriminatory, and the fragment patterns simple to interpret. PCR fingerprint analysis of variable tandem repeat loci in the T. mentagrophytes var. interdigitale NTS represents a valuable molecular typing method for future epidemiological investigations in this species.