The agony of choice in dermatophyte diagnostics—performance of different molecular tests and culture in the detection of Trichophyton rubrum and Trichophyton interdigitale

Comparative analysis in diagnosis by real-time polymerase chain reaction versus direct microscopy, culture, and histology in fungal infections of the nails, scalp, and skin

BACKGROUND

The diagnosis of superficial fungal infections is the subject of intensive research in many countries around the world. The diagnostic methods used are diverse, including both conventional and innovative techniques.

METHODS

This study evaluates the sensitivity, specificity, and efficacy of the real-time polymerase chain reaction (PCR) methodology and compares them with those of the conventional methods - direct microscopic, cultural, and histological examinations of materials from hair, skin, and nails - in order to demonstrate the benefits and significance of real-time PCR for the diagnosis of dermatophytic infections.

RESULTS

The values obtained for the sensitivity, specificity, and efficacy of direct microscopic, cultural, histological, and real-time PCR studies are as follows: 63.71, 88.89, and 72.96% (P < 0.001); 58.06, 100, and 73.47% (P < 0.001); 85.96, 100, and 90.70% (P < 0.001); 88.52, 100, and 92.63% (P < 0.001).

CONCLUSION

The use of real-time PCR in the diagnosis of dermatophytic infections is a relatively new approach in mycology and is subject to testing and experience from its use. The results are promising, but the method has not yet established itself as a new gold standard in the diagnosis of superficial fungal infections caused by dermatophytes, though its application would be very useful in identifying isolates without conidiogenesis or absence of growth.

Multiplex real-time PCR for skin fungal infections: The diagnostic reliability in a one-year non-interventional study

The skin fungal infection diagnostic workflow currently includes microscopic and culture-based methods as the gold standard. Recent published data described the possible limitations of these conventional techniques documenting the possibility of reducing response time intervals. The present study reports an evaluation of the DermaGenius® (DG) multiplex kit (PathoNostics) for rapid C. albicans and dermatophytes identification directly from skin samples. The investigations involved 90 specimens that underwent DNA extraction and amplification simultaneously to microscopic and culture methods. According to current guidelines, we defined a dermatophytic skin infection as the simultaneous presence of clinical evidence of skin lesions and positive results for dermatophyte elements from microscopy and/or cultures. The collected data remarked on the advantages of the molecular assay, especially in terms of sensitivity and rapidity. A statistical evaluation analysed a comparison between conventional and innovative diagnostic methods. The sensitivity, specificity, positive predictive value, and negative predictive value of DG-PCR in the cutaneous dermatophytosis were, respectively, 94.7%, 78.8%, 88.5%, and 89.6%. Based on our experience, the molecular technique could represent a diagnostic confirmation in the case of previous antifungal treatment, little biological material available, or urgent clinical conditions.

Antifungal Efficacy of Gallic Acid Extracted From Pomegranate Peel Against Trichophyton rubrum: In Vitro Case Study

Objectives: Trichophyton rubrum is one of the main pathogens causing superficial dermatophytosis, producing symptoms such as skin itching and pain, which seriously affects the quality of life of patients. Pomegranate peel extract is rich in gallic acid (GA), which has been reported to have biological effects including antifungal activity. However, the morphological and molecular mechanisms underlying the effects of GA on T rubrum are not well understood. The objectives of this study were to determine the antifungal efficacy of GA extracted from pomegranate peel against T rubrum in vitro, and to explore the underlying molecular mechanisms. Methods: The effects of 0-, 0.5-, and 1 mg/mL GA in pomegranate peel extract on T rubrum was investigated by detecting cell viability using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Transmission electron microscopy (TEM) was used to analyze the ultrastructure of T. rubrum, and transcriptome sequencing was used to analyze the enrichment pathway of differentially expressed genes. The identification of biosynthesis-related and key genes in the pathways involved using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) technology. Terbinafine hydrochloride (TERB) as a positive control group. Results: Pomegranate peel extract has a GA content of 1.0 mg/mL. Compared with untreated group, following treatment with 1.0 mg/mL GA content is rich in pomegranate peel extract, and the microstructure of T rubrum is destroyed. TEM results show that the number of lipid droplets in T rubrum was significantly increased, mitochondrial vacuoles degenerated, the serosa were damaged, and the boundary of thallus was unclear. In addition, 1 mg/mL GA can significantly inhibit T rubrum proliferation, and its inhibition ability is better than TERB. Transcriptomics results show that GA can change the gene expression profile of T rubrum, specifically: The biosynthesis was blocked, drug resistance was weakened, the transport of ATP-binding cassette (ABC) drugs transporter was increased, and the mitogen-activated protein kinase (MAPK) pathway was significantly inhibited. Conclusions: Pomegranate peel extract is rich in GA, which strongly inhibited the growth of T rubrum and reduced its drug resistance. This extract is a promising natural antifungal agent for clinical use.

In search of dermatophytes - frequency and etiology of fungal infections in patients with and without diabetes mellitus

INTRODUCTION

Onychomycosis is a frequent nail disorder, accounting for up to 50% of all nail problems. Treatment of onychomycosis is expensive and requires a long time of antifungal medications. Consequently, a proper and faster diagnosis is necessary. Especially for those patients with diabetes mellitus, where onychomycosis is among the most significant predictors of foot ulcer and possible severe complications.

[Clinical picture, causative agents and diagnostics of dermatomycoses]

Dermatomycoses affect free skin, hairy scalp, fingernails and toenails. In addition, oral mucosa and genital mucosa can also be affected by fungal infections. The most common pathogens causing skin fungal infections are dermatophytes. They are responsible for, among others, tinea corporis, tinea capitis and onychomycosis (tinea unguium). Mainly anthropophilic dermatophytes are found as pathogens. In the case of tinea capitis-at least in Europe and in German-speaking countries-zoophilic skin fungi must also be considered. Rarely, geophilic dermatophytes can also be isolated. Yeast infections of the skin, mostly caused by Candida albicans, primarily affect the intertriginous skin areas, for example, the groin region, but also the submammary area and the spaces between the fingers and toes. Elderly patients are often affected, but also infants and, in particular, immunocompromised patients. These patient groups are also more frequently affected by oral mucosal infections caused by Candida albicans and other Candida species. Pseudomembranous candidiasis of the oral mucosa and tongue typically affects patients with HIV/AIDS. Mold infections in dermatology are relevant in onychomycosis of the big toenail. The causative agent is usually Scopulariopsis brevicaulis. Cutaneous mold infections are rare and only occur in immunocompromised patients. The mycological diagnosis of dermatomycoses is based on the microscopic, if possible fluorescence-optical detection of fungal hyphae and spores from skin scales, nail shavings and hair roots. The culture detection of dermatophytes, yeasts and molds allows the identification of the causative fungal species, but often fails, especially in patients who have already been treated with antifungal agents. In view of the high sensitivity and specificity of the molecular methods for fungal detection compared to culture, polymerase chain reaction (PCR) must realistically be regarded as the gold standard for dermatophytosis diagnostics. However, it should not be neglected that the three pillars of diagnostics-preparation, culture, PCR-currently deliver the best results.

Metagenomics of Toenail Onychomycosis in Three Victorian Regions of Australia

Onychomycosis is a fungal disease of the nail that is found worldwide and is difficult to diagnose accurately. This study used metagenomics to investigate the microbiology of 18 clinically diagnosed mycotic nails and two normal nails for fungi and bacteria using the ITS2 and 16S loci. Four mycotic nails were from Bass Coast, six from Melbourne Metropolitan and eight from Shepparton, Victoria, Australia. The mycotic nails were photographed and metagenomically analysed. The ITS2 sequences for T. rubrum and T. interdigitale/mentagrophytes averaged over 90% of hits in 14/18 nails. The high abundance of sequences of a single dermatophyte, compared to all other fungi in a single nail, made it the most likely infecting agents (MLIA). Trichophyton rubrum and T. interdigitale/mentagrophytes were found in Bass Coast and Shepparton while only T. interdigitale/mentagrophytes was found in Melbourne. Two nails with T. interdigitale/mentagrophytes mixed with high abundance non-dermatophyte moulds (NDMs) (Aspergillus versicolor, Acremonium sclerotigenum) were also observed. The two control nails contained chiefly Fusarium oxysporum and Malassezia slooffiae. For bacteria, Staphylococcus epidermidis was in every nail and was the most abundant, including the control nails, with an overall mean rate of 66.01%. Rothia koreensis, Corynebacterium tuberculostearicum, and Brevibacterium sediminis also featured.

Rapid and Visual RPA-Cas12a Fluorescence Assay for Accurate Detection of Dermatophytes in Cats and Dogs

Dermatophytosis, an infectious disease caused by several fungi, can affect the hair, nails, and/or superficial layers of the skin and is of global significance. The most common dermatophytes in cats and dogs are Microsporum canis and Trichophyton mentagrophytes. Wood’s lamp examination, microscopic identification, and fungal culture are the conventional clinical diagnostic methods, while PCR (Polymerase Chain Reaction) and qPCR (Quantitative PCR) are playing an increasingly important role in the identification of dermatophytes. However, none of these methods could be applied to point-of-care testing (POCT). The recent development of the CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) based diagnostic platform promises a rapid, accurate, and portable diagnostic tool. In this paper, we present a Cas12a-fluorescence assay to detect and differentiate the main dermatophytes in clinical samples with high specificity and sensitivity. The Cas12a-based assay was performed with a combination of recombinase polymerase amplification (RPA). The results could be directly visualized by naked eyes under blue light, and all tested samples were consistent with fungal culture and sequencing results. Compared with traditional methods, the RPA-Cas12a-fluorescence assay requires less time (about 30 min) and less complicated equipment, and the visual changes can be clearly observed with naked eyes, which is suitable for on-site clinical diagnosis.

Trends in the epidemiology of dermatophytosis in the Middle East and North Africa region

Dermatophytosis corresponds to a broad series of infections, mostly superficial, caused by a group of keratinophilic and keratinolytic filamentous fungi called dermatophytes. These mycoses are currently considered to be a major public health concern worldwide, particularly in developing countries such as those in the Middle East and North Africa (MENA) region. Here we compiled and discussed existing epidemiologic data on these infections in the MENA region. Most of the available studies were based on conventional diagnostic strategies and were published before the last taxonomic revision of dermatophytes. This has led to misidentifications, which might have resulted in the underestimation of the real burden of these infections in the MENA countries. Our analysis of the available literature highlights an urgent need for further studies based on reliable diagnostic tools and standard susceptibility testing methods for dermatophytosis, which represents a major challenge for these countries. This is crucial for guiding appropriate interventions and activating antifungal stewardship programs in the future.

New Reference Genes for qRT-PCR Analysis as a Potential Target for Identification of Trichophyton verrucosum in Different Culture Conditions

Dermatophytes are a group of filamentous fungi infecting skin, hair, and nails that raise great diagnostic difficulties. qRT-PCR is a reliable technique for quantifying gene expression with increasingly frequent use in mycological diagnostics. Knowledge of genes and molecular markers with potential to be used in the identification of dermatophytes is of great importance for the development of this branch of diagnostics. In this article, the suitability of six candidate reference genes (TUBB, ACTB, ADPRF, RPL2, SDHA, and EEF1A1) was investigated for gene expression analysis in the dermatophyte Trichophyton verrucosum, which was cultured in various mycological media that are commonly used in a diagnostic laboratory, i.e., Sabouraud, potato dextrose, and keratin-supplemented MM-Cove. The different culture conditions are extremely important factors for the growth and physiology of dermatophytes. Gene expression stability was evaluated using geNorm, NormFinder, BestKeeper, and RefFinder algorithms. Regarding the stability of expression, SDHA was the most stable housekeeping gene; hence, this gene is recommended for future qRT-PCR studies on T. verrucosum strains. These results allow us to conclude that the SDHA gene can be an additional good candidate as an identification target in the qRT-PCR technique.

Commercial real time PCR implementation for rapid diagnosis of onychomycosis: A new workflow in a clinical laboratory

INTRODUCTION

Onychomycosis is a frequent and underdiagnosed condition. Approximately 90% of toenail onychomycosis infections are caused by dermatophytes, but classical diagnosis based on culture and microscopy observation is slow and has low sensitivity. Both limitations can be solved incorporating molecular techniques to routine diagnosis of onychomycosis.

OBJECTIVE

Prospective evaluation of the utility of incorporating in the clinical laboratory workflow a commercial real time PCR (qPCR) for dermatophytes detection in nails after potassium hydroxide direct observation screening.

MATERIALS AND METHODS

152 nail samples were included (34 KOH negative and 118 KOH positive) and processed by culture and qPCR.

RESULTS

In the negative KOH group, only one dermatophyte grew in culture and three were detected by qPCR. In the group of positive KOH, 57 dermatophytes grew in culture and 81 were detected by qPCR. In this group, 25% of diagnosed dermatophytes were detected only by qPCR. The sensitivity of qPCR compared to culture is 92.8% and time of response decreases from days to hours.

CONCLUSION

Based in our results, we propose a workflow algorithm for a clinical laboratory that eliminates culture for qPCR positive samples.

Multiplex RT-PCR provides improved diagnosis of skin and nail dermatophyte infections compared to microscopy and culture: a laboratory study and review of the literature

Dermatophytes are the most common cause of superficial mycosis, estimated to affect 20% to 25% of the general population. We assessed the performance of a novel real-time polymerase chain reaction (RT-PCR) multiplex assay for diagnosis of dermatophytosis. To evaluate sensitivity and specificity, 10 known bacteria and 10 known fungi commonly found on skin, as well as 105 samples with culture confirmed dermatophytosis were tested using Dermatophyte and Fungi assay (AusDiagnostics, Sydney, Australia), a novel multiplex assay for diagnosis of dermatophytosis in skin and nail. This was followed by prospective evaluation of 195 clinical samples for dermatophytosis by both conventional methods and RT-PCR. RT-PCR showed almost two-fold higher sensitivity and high specificity in the diagnosis of skin and nail dermatophytosis compared to traditional microscopy and culture. In addition, RT-PCR demonstrated markedly reduced turnaround time from 4 to 6 weeks to 4 to 6 hours and ability for high throughput.

Recent trends in rapid diagnostic techniques for dermatophytosis

Dermatophytosis is a common contagious disease of both humans and animals. It is caused by a group of filamentous fungi known as dermatophytes, including several genera and various species. An accurate diagnosis of dermatophytes as a causative agent of a skin lesion requires up to one month of conventional laboratory diagnostics. The conventional gold standard diagnostic method is a direct microscopic examination followed by 3 to 4 weeks of Sabouraud's dextrose agar (SDA) culturing, and it may require further post-culturing identification through biochemical tests or microculture technique application. The laborious, exhaustive, and time-consuming gold standard method was a real challenge facing all dermatologists to achieve a rapid, accurate dermatophytosis diagnosis. Various studies developed more rapid, accurate, reliable, sensitive, and specific diagnostic tools. All developed techniques showed more rapidity than the classical method but variable specificities and sensitivities. An extensive bibliography is included and discussed through this review, showing recent variable dermatophytes diagnostic categories with an illustration of weaknesses, strengths, and prospects.

German-Wide Analysis of the Prevalence and the Propagation Factors of the Zoonotic Dermatophyte Trichophyton benhamiae

For about 10 years, a new variant of the pathogen Trichophyton (T.) benhamiae has appeared in Germany, characterized by a previously unobserved culture phenotype with a strong yellow reverse. A few studies suggest that this new variety is now the most common zoophilic dermatophyte in Germany. The guinea pig is the main carrier. Exact prevalence measurements are not yet available. Thus, the aim of our ongoing study was to collect data on the frequency and geographic distribution of the pathogen and its phenotypes (white and yellow) in humans and guinea pigs throughout Germany. Our former studies have already shown that animals from large breeding farms are particularly heavily affected. In contrast to this, 21 small, private breedings were sampled and husbandry conditions recorded. This placed us in a position to identify propagation factors and to give recommendations for containment. For animals from private breedings, we detected T. benhamiae with a prevalence of 55.4%, which is a reduction of nearly 40% compared with animals from large breeding farms. As risk factors, we identified the type of husbandry and the contact to other breedings. Furthermore, certain animal races, like Rex guinea pigs and races with long hair in combination with curls were predestined for colonization with T. benhamiae due to their phenotypic coat characteristics. A prevalence for infections with T. benhamiae of 36.2% has been determined for symptomatic pet guinea pigs suspected of having dermatophytosis and is comparable to the study of Kraemer et al. showing a prevalence of 34.9% in 2009 in Germany. The prevalence in humans is stable with about 2-3% comparing the data of 2010-2013 and 2018 in Thuringia. The new type of T. benhamiae was by far the most frequent cause in all settings.

Detection and identification of dermatophytes based on currently available methods - a comparative study

AIMS

Accurate identification of dermatophytes is essential for implementing appropriate antifungal treatment and epidemiological analysis. However, the limitations of conventional diagnostics are a frequently discussed topic, and new diagnostic techniques are constantly expanding. In this study, we assess the suitability of conventional diagnostic techniques in comparison to the real-time PCR assay and MALDI-TOF MS in detection and identification of dermatophytes.

METHODS AND RESULTS

Strains included in this study were obtained from human and animals with symptomatic, and asymptomatic infection. A direct examination revealed that 31·7 and 60·9% of samples from symptomatic patients, and 25·7 and 60% from asymptomatic animals were positive, as shown by light and fluorescence microscopy respectively. In turn, dermatophytes were isolated from 90·2 and 71·4% of these samples. The pan-dermatophyte primers in real-time PCR assay facilitated detection in 85·3 and 82·9% of the symptomatic and asymptomatic dermatophytoses respectively. Additionally, species-specific PCR assays were positive in 70·7 and 37·1% of these samples. The MALDI-TOF MS analysis yielded positive results consistent with conventional techniques in 97·2 and 72% of symptomatic and asymptomatic infections respectively.

CONCLUSIONS

Our study revealed that there is no universal diagnostic method that would be ideal in each of the cases considered. Nonetheless, conventional techniques are still the most effective and reliable tools for mycological diagnostics.

SIGNIFICANCE AND IMPACT OF THE STUDY

Dermatologists and veterinarians have difficulties in making a diagnosis of dermatophytoses based only on observed symptoms of fungal infections, as they mimic symptoms of other dermatoses. In this context, a comparative analysis of the results of diagnostics performed using conventional methods and new technologies are crucial for implementing these pioneer methods into routine laboratory practice.

Commercial real time PCR implementation for rapid diagnosis of onychomycosis: A new workflow in a clinical laboratory

INTRODUCTION

Onychomycosis is a frequent and underdiagnosed condition. Approximately 90% of toenail onychomycosis infections are caused by dermatophytes, but classical diagnosis based on culture and microscopy observation is slow and has low sensitivity. Both limitations can be solved incorporating molecular techniques to routine diagnosis of onychomycosis.

OBJECTIVE

Prospective evaluation of the utility of incorporating in the clinical laboratory workflow a commercial real time PCR (qPCR) for dermatophytes detection in nails after potassium hydroxide direct observation screening.

MATERIALS AND METHODS

152 nail samples were included (34 KOH negative and 118 KOH positive) and processed by culture and qPCR.

RESULTS

In the negative KOH group, only one dermatophyte grew in culture and three were detected by qPCR. In the group of positive KOH, 57 dermatophytes grew in culture and 81 were detected by qPCR. In this group, 25% of diagnosed dermatophytes were detected only by qPCR. The sensitivity of qPCR compared to culture is 92.8% and time of response decreases from days to hours.

CONCLUSION

Based in our results, we propose a workflow algorithm for a clinical laboratory that eliminates culture for qPCR positive samples.

Recent advances in the diagnosis of dermatophytosis

Dermatophytosis is a disease of global significance caused by pathogenic keratinolytic fungi called dermatophytes in both animals and humans. The recent taxonomy of dermatophytes classifies them into six pathogenic genera, namely Microsporum, Trichophyton, Epidermophyton, Nannizzia, Lophophyton and Arthroderma. It is because of the delayed diagnostic nature and low accuracy of dermatophyte detection by conventional methods that paved the path for the evolution of molecular diagnostic techniques, which provide the accurate and rapid diagnosis of dermatophytosis for an appropriate, timely antifungal therapy that prevents the nonspecific over-the-counter self-medication. This review focuses on the importance of rapid and accurate diagnosis of dermatophytosis, limitations of conventional methods, selection of targets in diagnosis, and factors affecting sensitivity and specificity of various molecular diagnostic technologies in the diagnosis of dermatophytosis. Generally, all the molecular techniques have a significant edge over the conventional methods of culture and microscopy in the dermatophytosis diagnosis. However, in mycology laboratory, the suitability of any molecular diagnostic technique in the diagnosis of dermatophytosis is driven by the requirement of time, economy, complexity, the range of species spectrum detected and the scale of diagnostic output required. Thus, various choices involved in the pursuit of a diagnosis of dermatophytosis are determined by the available conditions and the facilities in the laboratory.

[Dermatophytosis caused by rare anthropophilic and zoophilic agents]

The basis for effective treatment of any dermatomycosis is the correct and timely identification of the pathogen, which allows the targeted choice of the most suitable antimycotic and is important for the prevention of repeated infections. In recent years, infections with dermatophytes seem to have increased. In fact, from 2007 to 2018, there was an increase in the number of samples processed in the Mycology Laboratory of the Department of Dermatology at the University Hospital Jena. The most common isolated dermatophytes between 2007 and 2018 were Trichophyton (T.) rubrum, T. interdigitale, Microsporum (M.) canis and T. benhamiae. However, dermatophytoses may also be caused by rare anthropophilic agents such as Epidermophyton floccosum, zoophiles such as T. verrucosum, T. quinckeanum or Nannizzia (N.) persicolor as well as by geophiles such as N. gypsea. Therefore, these dermatophytes should at least be known, so that in case of unusual observations investigations can be performed accordingly. Changes in the pathogen spectrum of dermatophytoses have taken place over time and it is expected that the occurrence of dermatophytes will be subject of continuous fluctuations, which may mean that the incidence of some of these "rare" dermatophytes, as described here in five clinical examples, may be changing.

Predominance of Trichophyton interdigitale Revealed in Podiatric Nail Dust Collections in Eastern Australia

Toenail onychomycosis caused by dermatophytes is a significant medical and financial worldwide burden. Relatively scant research has been undertaken as to the predominant species and strains causing this condition in Australia, which is a unique isolated continent with diverse geographical, climatic and population regions. Four regions were selected in Eastern Australia: Far North Queensland, Rural Victoria, Melbourne Metropolitan and Tasmania. From each of these areas, communal nail dust bags from podiatric physicians' work were collected and analysed. A total of 32 dust bags were collected: 10 from Far North Queensland, 8 from Melbourne Metropolitan, 8 from Rural Victoria and 6 from Tasmania. Dermatophyte test medium was used to isolate dermatophytes from the dust, and the colonies were subcultured to Potato Dextrose Agar. Of the bags collected, in total 69% were positive for dermatophytes: 40% from Far North Queensland, 75% from Melbourne Metropolitan, 88% from Rural Victoria and 83% from Tasmania. The internal transcribed spacer (ITS) region of ribosomal DNA was used to identify and compare isolates. A total of 148 dermatophyte strains were identified. The predominant species isolated was Trichophyton interdigitale (125 isolates), which was found in all four regions. This species was further subdivided into four ITS genotypes: the first two were present in all regions, but the third was found only in the Melbourne Metropolitan area and the fourth only in Tasmania. Only one strain of Trichophyton rubrum was found and only in Rural Victoria. Eighteen isolates of Arthroderma quadrifidum were cultured from Rural Victoria and Tasmania and were further classified into three ITS genotypes. Some isolates rarely reported in clinical material were identified as Paraphyton cookei, Arthroderma tuberculatum and Arthroderma crocatum. A potentially new species of Arthroderma was also found in Melbourne Metropolitan. These findings reveal a unique dermatophyte fingerprint in toenails for Eastern Australia.

[Genome detection of dermatophytes : Current findings from the external quality assessment test]

In addition to morphological diagnostics, molecular methods have become available for the diagnosis of suspected dermatophytoses. Since March 2016, INSTAND e. V., in cooperation with the National Reference Laboratory for Dermatophytes, has provided an external quality assessment (EQA) test for the genome detection of dermatophytes twice a year. More than half of the participants used commercial kits for the analysis of the samples. All kits with a high level of accuracy correctly determined the presence of Trichophyton rubrum or no dermatophytes. In species diagnostics beyond Trichophyton rubrum there are large differences between the kits. These are examined in more detail based on clinical studies and the results of the EQA test.

Clinical evaluation of the DermaGenius® Nail real-time PCR assay for the detection of dermatophytes and Candida albicans in nails

Onychomycosis represents one of the most frequent mycoses in the world. Causative agents are mainly dermatophytes, but yeasts and nondermatophyte moulds can also be involved. Conventional diagnostic methods include direct microscopy (or histology) and culturing. However, molecular methods are becoming increasingly popular in this field. The DermaGenius® (DG) Nail multiplex assay (PathoNostics, The Netherlands) is a new commercial real-time polymerase chain reaction (PCR) kit, which can detect Trichophyton rubrum, Trichophyton interdigitale and Candida albicans directly in nails. The present study is a retrospective evaluation of the kit applied to 138 finger and toenail clippings in comparison to histology and culture methods. The sensitivity and specificity of the PCR assay are 80% (76/95) and 74.4% (32/43), respectively, when histology and culture are used as reference to define onychomycosis. DG performance is not different from histology combined with culture (P = .11) but the best diagnostic efficacy (88.4%, 122/138) is obtained by the combination of histology and DG. In conclusion, this study emphasizes the clinical usefulness of the DG in diagnostics. The high specificity of this test guarantees a better identification compared to culture that can lead to dermatophyte misidentifications. It is a reliable PCR assay that shortens the time to diagnosis and can unmask the presence of nongrowing fungal pathogens in nails.

Trichophyton mentagrophytes - a new genotype of zoophilic dermatophyte causes sexually transmitted infections

BACKGROUND

A new genotype of the zoophilic fungal species Trichophyton (T.) mentagrophytes was recently described in two studies. It was isolated from three patients who had visited Southeast Asia and one patient who had visited Egypt. In contrast to these studies, we have observed a number of cases with the dimensions of an epidemic outbreak.

PATIENTS AND METHODS

At the University Hospital Charité Berlin, 43 patients, mostly suffering from highly inflammatory, painful and persistent infections of the pubogenital region were observed between January 2016 and July 2017. Mycological examination was performed with fungal culture and sequencing of the ITS (internal transcribed spacer) region of the ribosomal DNA. Three additional genomic regions were spot-checked.

RESULTS

In 37 of the cases, a new genotype of T. mentagrophytes (referred to here as T. mentagrophytes VII) was isolated as the etiological agent, and sequencing revealed identical sequences for all isolates. Most of the infected patients had no history of travel, and only two patients reported contact with animals.

CONCLUSIONS

The new genotype clustered phylogenetically among the strains of the zoophilic species T. mentagrophytes with four different DNA markers. While human-to-human transmission of zoophilic dermatophytes is rare, transmission via sexual contact seemed to be quite effective here.

Assessment of a pan-dermatophyte nested-PCR compared with conventional methods for direct detection and identification of dermatophytosis agents in animals

Conventional direct microscopy with potassium hydroxide (KOH) and culture were found to lack the ability to establish a fast and specific diagnosis of dermatophytosis. A pan-dermatophyte nested-PCR assay was developed using a novel primer pair targeting the translation elongation factor 1-α (Tef-1α) sequences for direct detection and identification of most veterinary relevant dermatophytes in animal samples suspected to dermatophytosis. A total of 140 animal skin and hair samples were subjected to direct microscopy, culture, and ITS-RFLP/ITS-sequencing of culture isolates for the detection and identification of dermatophytosis agents. Nested-PCR sequencing was performed on all the extracted DNAs using a commercial kit after dissolving the specimens by mechanical beating. Nested-PCR was positive in 90% of samples, followed by direct microscopy (85.7%) and culture (75%). The degree of agreement between nested-PCR and direct microscopy (94.4%) was higher than with culture (83.3%). In 105 culture-positive cases, the measures of agreement for the identification of dermatophytosis agents were as follows: 100% between nested-PCR sequencing and ITS-RFLP/ITS-sequencing and 63.8% between nested-PCR sequencing and culture. The developed nested-PCR was faster as well as more sensitive and specific than conventional methods for detection and identification of dermatophytes in clinical samples, which was particularly suitable for epidemiological studies.

Fast identification of dermatophytes by MALDI-TOF/MS using direct transfer of fungal cells on ground steel target plates

Dermatophytes cause human infections limited to keratinised tissues. We showed that the direct transfer method allows reliable identification of non-dermatophytes mould and yeast by MALDI-TOF/MS. We aimed at assessing whether the direct transfer method can be used for dermatophytes and whether an own mass spectra library would be superior to the Bruker library. We used the Bruker Biotyper to build a dermatophyte mass spectra library and assessed its performance by 1/testing a panel of mass spectrum produced with strains genotypically identified and, 2/comparing MALDI-TOF/MS identification to morphology-based methods. Identification of dermatophytes using the Bruker library is poor. Our library provided 97% concordance between ITS sequencing and MALDI-TOF/MS analysis with a panel of 1104 spectra corresponding to 276 strains. Direct transfer method using unpolished target plates allowed proper identification of 85% of dermatophytes clinical isolates most of which were common dermatophytes. A homemade dermatophyte MSP library is a prerequisite for accurate identification of species absent in the Bruker library but it also improves identification of species already listed in the database. The direct deposit method can be used to identify the most commonly found dermatophytes such as T. rubrum and T. interdigitale/mentagrophytes by MALDI-TOF/MS.