Towards a rapid identification and a novel proteomic analysis for dermatophytes from human and animal dermatophytosis

Establishment and application of multiplex PCR method for detection of Trichophyton verrucosum, Microsporum canis, and Trichophyton mentagrophytes from cattle

Introduction

Dermatophytosis, which is a contagious fungal skin infection common in animals and humans, is the most common skin disease in cattle. It has a serious negative impact on the livestock industry. In order to circumvent the shortcomings of traditional detection methods such as time-consuming and low isolation rate. Therefore, this study established a simple, rapid and effective diagnostic method to accurately diagnose and differentiate the causative fungi of dermatophytosis, which is of great significance to enhance the prevention and treatment of dermatophytosis in beef cattle farms.

Methods

Three pairs of specific primers were designed using Primer Premier 5.0 from Trichophyton verrucosum, Microsporum canis and Trichophyton mentagrophytes. A triple PCR assay was established by optimising the primer dose and annealing temperature to improve the detection sensitivity. The feasibility of the method was verified by testing the samples.

Results and discussion

In this study, a multiplex PCR method that can rapidly detect these three fungi at the same time was established, and its specificity, sensitivity and repeatability were analyzed at the same time. The results showed that the multiplex PCR method amplified the specific expected fragments of 581 bp, 1,513 bp and 371 bp for T. verrucosum, M. canis and T. mentagrophytes. The minimum detection limits of T. verrucosum, M. canis and T. mentagrophytes were all 1 pg./μL. The positive rates were 87.5% (21/24) for samples. The results showed that the multiplex PCR method was simple, specific and sensitive and might be used for rapid diagnosis and identification of dermatophytes in cattle.

First Step on the Way to Identify Dermatophytes Using Odour Fingerprints

The clinical diagnosis of dermatophytosis and identification of dermatophytes face challenges due to reliance on culture-based methods. Rapid, cost-effective detection techniques for volatile organic compounds (VOCs) have been developed for other microorganisms, but their application to dermatophytes is limited. This study explores using VOCs as diagnostic markers for dermatophytes. We compared VOC profiles across different dermatophyte taxa using solid-phase microextraction (SPME) and advanced analytical methods: gas chromatography-mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS). We analyzed 47 dermatophyte strains from 15 taxa grown on sheep wool, including clinically significant species. Additionally, we examined phylogenetic relationships among the strains to correlate genetic relatedness with metabolite production. Our results showed that GC×GC-TOFMS offered superior resolution but similar differentiation of VOC profiles compared to GC-MS. VOC spectra allowed reliable distinction of taxonomic units at the species level and below, however, these distinctions showed only a slight correlation with phylogenetic data. We identified pan-dermatophyte and species- or strain-specific VOC profiles, indicating their potential for rapid, non-invasive detection of dermatophyte infections, including epidemic strains. These patterns could enable future taxa-specific identification. Our study highlights the potential of VOCs as tools for dermatophyte taxonomy and diagnosis.

Development and Clinical Detection of Rapid Molecular Diagnostic System for Pathogenic Dermatophytes of Tinea Capitis of Multiple Centres in China

OBJECTIVES

Tinea capitis remains a common fungal infection in children worldwide. Species identification is critical for determining the source of infection and reducing transmission. In conventional methods, macro- and microscopic analysis is time-consuming and results in slow fungal growth or low specificity. We propose a rapid real-time diagnostic PCR method that allows species-specific identification of dermatophytes, including the Microsporum canis complex, Trichophyton mentagrophytes complex, Trichophyton rubrum complex and Trichophyton tonsurans, in patients with tinea capitis.

METHODS

Hair and scrapings samples were collected from 231 patients with tinea capitis who were positive for fungal elements via direct microscopy with potassium hydroxide. Each sample was subjected to a two-step real-time PCR (RT-PCR) assay, which was designed on the basis of differences in the DNA fragments of the internal transcribed spacer (ITS) and β-tubulin covering the Microsporum canis complex, T. mentagrophyte complex, T. rubrum complex, T. tonsurans, T. verrucosum, T. schoenleinii and N. gypseum.

RESULTS

In total, 186/231 samples (80.52%) were positive for fungal culture. The two-step RT-PCR was positive in 215/231 samples (93.07%), among which 179 were culture positive. The combined efficacy was 96.81%, which was significantly different when the RT-PCR assays were performed in parallel with fungal culture. A total of 126 samples (54.55%) were identified as Microsporum canis by fungal culture, among which the positive rate of M. canis complex RT-PCR was 97.62% (123/126). A total of 45 samples were negative for fungal culture, of which 80.0% (36/45) were positive by RT-PCR, and the percentage of M. canis complex-positive samples was 53.33% (24/45). The RT-PCR assays were negative for 16/231 samples, among which 7 were culture positive, including M. canis (n = 3), T. violaceum (n = 3) and N. gypseum (n = 1).

CONCLUSION

We developed a new diagnostic assay system using a rapid real-time TaqMan PCR assay with specific primers that can be applied in routine laboratory practice for hair and skin samples of tinea capitis to detect dermatophytes and increase diagnostic efficiency.

Exploring the Complexity of the Interaction between T. rubrum and S. aureus/S. epidermidis in the Formation of Polymicrobial Biofilms

Dermatophytes associated with bacteria can lead to severe, difficult-to-treat infections and contribute to chronic infections. Trichophyton rubrum, Staphylococcus aureus, and Staphylococcus epidermidis can form biofilms influenced by nutrient availability. This study investigated biofilm formation by these species by utilizing diverse culture media and different time points. These biofilms were studied through scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), biomass, metabolic activity, and colony-forming units (CFUs). The results revealed that mixed biofilms exhibited high biomass and metabolic activity when cultivated in the brain heart infusion (BHI) medium. Both bacterial species formed mature biofilms with T. rubrum within 72 h, irrespective of media. The timing of bacterial inoculation was pivotal in influencing biomass and metabolic activity. T. rubrum's development within mixed biofilms depended on bacterial addition timing, while pre-adhesion influenced fungal growth. Bacterial communities prevailed initially, while fungi dominated later in the mixed biofilms. CLSM revealed 363 μm thick T. rubrum biofilms with septate, well-developed hyphae; S. aureus (177 μm) and S. epidermidis (178 μm) biofilms showed primarily cocci. Mixed biofilms matched T. rubrum's thickness when associated with S. epidermidis (369 μm), with few hyphae initially. Understanding T. rubrum and Staphylococcal interactions in biofilms advances antimicrobial resistance and disease progression knowledge.

Subtilisin 3 production from Microsporum canis is independent of keratin substrate availability

Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. We investigated a critical adhesion protein, subtilisin 3, utilized by Microsporum canis during initial stages of infection, analyzing its production and expression under varying growth conditions. Additionally, as this protein must be expressed and produced for dermatophyte infections to occur, we developed and optimized a diagnostic antibody assay targeting this protein. Subtilisin 3 levels were increased in culture when grown in baffled flasks and supplemented with either l-cysteine or cat hair. As subtilisin 3 was also produced in cultures not supplemented with keratin or cysteine, this study demonstrated that subtilisin 3 production is not reliant on the presence of keratin or its derivatives. These findings could help direct future metabolic studies of dermatophytes, particularly during the adherence phase of infections.

Global Demographic Characteristics and Pathogen Spectrum of Tinea Capitis

Tinea capitis is an important superficial fungal infection with a global distribution. It mainly affects prepubertal children and is more common in males. Anthropophilic and zoophilic dermatophytes are responsible for most infections. The pathogen spectrum of tinea capitis varies across different regions and changes over time, and is influenced by multiple factors, such as economic development, changes in lifestyle, immigration and animal distribution. This review aimed to clarify the demographic and etiological characteristics of tinea capitis worldwide and determine the common trends of causative pathogens. By mainly analyzing the literature published from 2015 to 2022, we found that the incidence and demographic characteristics of tinea capitis remained generally stable. Zoophilic Microsporum canis, anthropophilic Trichophyton violaceum and Trichophyton tonsurans were the predominant pathogens. The pathogen spectra in different countries changed in different directions. In some countries, the main pathogen shifted to an anthropophilic dermatophyte, such as T. tonsurans, Microsporum audouinii or T. violaceum; in contrast, it shifted to a zoophilic agent, such as M. canis, in some other countries. Dermatologists are advised to continue monitoring the pathogen spectrum and implement preventive measures according to the reported changes.

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.

OMICS and Other Advanced Technologies in Mycological Applications

Fungi play many roles in different ecosystems. The precise identification of fungi is important in different aspects. Historically, they were identified based on morphological characteristics, but technological advancements such as polymerase chain reaction (PCR) and DNA sequencing now enable more accurate identification and taxonomy, and higher-level classifications. However, some species, referred to as "dark taxa", lack distinct physical features that makes their identification challenging. High-throughput sequencing and metagenomics of environmental samples provide a solution to identifying new lineages of fungi. This paper discusses different approaches to taxonomy, including PCR amplification and sequencing of rDNA, multi-loci phylogenetic analyses, and the importance of various omics (large-scale molecular) techniques for understanding fungal applications. The use of proteomics, transcriptomics, metatranscriptomics, metabolomics, and interactomics provides a comprehensive understanding of fungi. These advanced technologies are critical for expanding the knowledge of the Kingdom of Fungi, including its impact on food safety and security, edible mushrooms foodomics, fungal secondary metabolites, mycotoxin-producing fungi, and biomedical and therapeutic applications, including antifungal drugs and drug resistance, and fungal omics data for novel drug development. The paper also highlights the importance of exploring fungi from extreme environments and understudied areas to identify novel lineages in the fungal dark taxa.

Prevalence and Risk Factors of Superficial Fungal Infection among Patients Attending a Tertiary Care Hospital in Central Nepal

Fungal infections of hair, nail, and skin are common worldwide and tend to increase. The present study was conducted to determine the prevalence of dermatomycoses, estimate the efficiency of rapid potassium hydroxide (KOH) wet-mount, and observe the hygienic status and the predisposing risk factors. Altogether 115 samples (nail = 77, skin = 30, and hair = 8) were obtained in a duration of December 2019 to June 2020 at Grande International Hospital, Nepal. The samples were examined by KOH wet-mount microscopy and further processed for culture. The dermatophyte test medium (DTM) was used to isolate dermatophytes separately. The fungal colonies obtained in SDA, SDA with cycloheximide/chloramphenicol and dermatophyte medium were subjected to lactophenol cotton blue (LPCB) reagent to study fungal morphology. The yeast colonies grown on SDA were subjected to Gram staining, germ-tube tests, and biochemical tests for identification. CHROMagar was used to distinguish different Candida species based on its pigment production in the medium. Various factors (age, sex, occupation, and hygiene condition) were analyzed which were associated with mycological infection. Out of 115 samples, the presence of fungal elements was detected in 20 samples by KOH. Nondermatophyte molds were the most isolated fungus in nails, skin, and hair, followed by yeast and dermatophytes, respectively. Dermatomycosis molds were the most common causative agents with 22 (14.7%) cases, followed by yeasts with 6 (5.21%) cases. Candida albicans was isolated from 5 (4.3%) cases, whereas Rhodotorula species accounted for a single (0.8%) case. Dermatophytes were isolated from 5 (4.3%) cases. Among them, n = 4(3.4%) cases revealed Trichophyton rubrum and Trichophyton mentagrophytes was isolated from single (0.8%) case. The most isolated nondermatophyte mold that follows criteria as a pathogen in our study was Cladosporium species 6 (25%) out of 27 total fungal isolates. Poor hygiene and sweating were found to be statistically significant (P < 0.05) in fungal cases detected by both KOH and culture. Dermatophytes and nondermatophyte fungi were emerging as important causes of fungal infection. Both direct microscopy and culture followed by LPCB together were vital tools for the diagnosis of fungal infections.

Comparison of Fungal Fluorescent Staining and ITS rDNA PCR-based Sequencing with Conventional Methods for Diagnosis of Onychomycosis

Accurate identification of fungal causes for onychomycosis is essential for proper treatment. Presently available laboratory methods show unreliable sensitivity; so there is a requirement for innovative detection techniques. The aim for this work was to assess the efficiencies of fluorescent staining and internal transcribed spacer (ITS) ribosomal DNA (rDNA) polymerase chain reaction (PCR)-based sequencing in comparison to conventional techniques for diagnosis of onychomycosis. Nail specimens obtained from 100 patients with clinically- diagnosed onychomycosis were analyzed. Nail scrapings or clippings were subjected to direct microscopic examination by KOH mount, culture by using Sabouraud’s dextrose agar and histopathological examination with periodic-acid Schiff (PAS). Collected specimens were subsequently examined by fluorescent staining and PCR-based sequencing (30 specimens only) to compare the feasibility, sensitivity and diagnostic accuracy for these two methods. The most frequently isolated fungi were yeasts (39/76: 51.3%), dermatophytes (24/76; 31.6%) and non-dermatophyte molds (NDMs) (13/76; 17.1%). Mixed mycotic infections were recovered from 6% of the collected nail specimens. The positive detection rates were significantly different between KOH examinations (52%), nail plate histology (55%), fungal culture (70%) and fluorescent staining (80%). Considering fungal culture as the gold standard, the most sensitive technique was PCR (100%) followed by fluorescent staining (89%), PAS staining (69%) while the least sensitive technique was KOH mount (53%). Fluorescence staining can be used as a rapid and high-yield technique for identification of fungi in the specimens. PCR-based sequencing was highly sensitive and faster compared to culture. Whenever possible, it enables species identification with higher adequacy.

A Comparative Study on the Phenotypic Versus Molecular Identification of Clinical Dermatophytes

Dermatophytosis is the superficial infection of keratinized tissue like skin, hair, and nails, in humans and animals, by a group of closely related fungi known as dermatophytes. Phenotypic identification of dermatophytes, especially through classical methods can be difficult and uncertain at times, especially when differentiating species with overlapping characteristics. Alternative identification methods based on amplification and sequence analysis of the highly polymorphic internal transcribed spacer (ITS) sequences flanking the 5.8S ribosomal RNA gene has proven to be quite sensitive and reliable. The objective of our study was to compare the phenotypic and the ITS sequencing-based methods for the identification of clinically isolated dermatophyte specimens from Puducherry, India. A total of 13 clinical samples from 39 suspected cases were found positive for dermatophytes using KOH/DMSO preparations. Specimens were subsequently cultured in Sabouraud dextrose agar (SDA) supplemented with chloramphenicol, gentamicin, and cycloheximide. Dermatophytes were identified based on culture characteristics and microscopic examination in lactophenol cotton blue preparations. ITS sequencing was additionally performed after PCR amplification for species identification. Identification based on phenotype through microscopy and culture methods confirmed infections with Trichophyton mentagrophytes (n = 11), T. rubrum (n = 1), and Microsporum gypseum (n = 1). The strains were confirmed by ITS sequencing without any discrepancy with phenotypic identification. Identification of common dermatophytes based on phenotypic characteristics may be used as a reliable method of diagnosis where sophisticated methods like ITS sequencing and PCR are unavailable.

Characterization and Antidermatophyte Activity of Henna Extracts: A Promising Therapy for Humans and Animals Dermatophytoses

Dermatophytoses representing a major global health problem and dermatophyte species with reduced susceptibility to antifungals are increasingly reported. Therefore, we investigated for the first time the antidermatophyte activity and phytochemical properties of the sequential extracts of the Egyptian privet Henna (Lawsonia inermis) leaves. Total phenolic content (TPC), total flavonoids (TF), and antioxidant activity of chloroform, diethyl ether, acetone, ethanol 80%, and aqueous extracts were evaluated. The antifungal activity of henna leaves extracts (HLE) toward 30 clinical dermatophytes isolates, including Trichophyton mentagrophytes, Microsporum canis, and T. rubrum, was determined. Morphological changes in hyphae were investigated using scanning electron microscopy (SEM) analysis. Following the polarity of ethanol and acetone, they exhibited distinct efficiency for the solubility and extraction of polyphenolic polar antioxidants from henna leaves. Fraxetin, lawsone, and luteolin-3-O-glucoside were the major phenolic compounds of henna leaves, as assessed using high-performance liquid chromatography analysis. A high and significant positive correlation was found between TPC, TF, the antioxidants, and the antidermatophyte activities of HLE. Acetone and ethanol extracts exhibited the highest antifungal activity toward the tested dermatophyte species with minimum inhibitory concentration (MIC) ranges 12.5-37.5 and 25-62.5 µg/mL, respectively. Structural changes including collapsing, distortion, inflating, crushing of hyphae with corrugation of walls, and depressions on hyphal surfaces were observed in SEM analysis for dermatophyte species treated with MICs of griseofulvin, acetone, and ethanol extracts. In conclusion, acetone and ethanolic extracts of henna leaves with their major constituent fraxetin exhibited effective antifungal activity toward dermatophyte species and may be developed as an alternative for dermatophytosis treatment. These findings impart a useful insight into the development of an effective and safe antifungal agent for the treatment of superficial fungal infections caused by dermatophytes.

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.

Real-Time PCR as an Alternative Technique for Detection of Dermatophytes in Cattle Herds

Dermatophytes are filamentous fungi with the ability to digest and grow on keratinized substrates. The ongoing improvements in fungal detection techniques give new scope for clinical implementations in laboratories and veterinary clinics, including the monitoring of the disease and carrier status. The technologically advanced methods for dermatophyte detection include molecular methods based on PCR. In this context, the aim of this study was to carry out tests on the occurrence of dermatophytes in cattle herds using qPCR methods and a comparative analysis with conventional methods. Each sample collected from ringworm cases and from asymptomatic cattle was divided into three parts and subjected to the real-time PCR technique, direct light microscopy analysis, and culture-based methods. The use of the real-time PCR technique with pan-dermatophyte primers detected the presence of dermatophytes in the sample with a 10.84% (45% vs. 34.17%) higher efficiency than direct analysis with light microscopy. Moreover, a dermatophyte culture was obtained from all samples with a positive qPCR result. In conclusion, it seems that this method can be used with success to detect dermatophytes and monitor cowsheds in ringworm cases and carriers in cattle.

Matrix-Assisted Laser Desorption Ionization Time-of-Flight for Fungal Identification

Many studies have shown successful performance of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for rapid yeast and mold identification, yet few laboratories have chosen to apply this technology into their routine clinical mycology workflow. This review provides an overview of the current status of matrix-assisted laser desorption ionization time-of-flight mass spectrometry for fungal identification, including key findings in the literature, processing and database considerations, updates in technology, and exciting future prospects. Significant advances toward standardization have taken place recently; thus, accurate species-level identification of yeasts and molds should be highly attainable, achievable, and practical in most clinical laboratories.

Evaluation of activity and toxicity of combining clioquinol with ciclopirox and terbinafine in alternative models of dermatophytosis

Dermatophytosis is a superficial fungal infection that affects humans and is very common in small animals. The treatment using the most commonly used antifungals is failing, and new therapeutic alternatives are required to combat the resistance of these fungal infections. Previous studies by the group have shown that clioquinol is an important therapeutic alternative in the treatment of dermatophytosis. The object was to conduct studies of antidermatophytic activity and the irritant potential from the double and triple combinations of clioquinol, terbinafine and ciclopirox in ex vivo and in vivo alternative models. To evaluate the irritant potential of antifungal combinations, the alternative HET-CAM method (chicken egg test chorioallantoic membrane) was used. Ex vivo models were used to assess the effectiveness of antifungal combinations, using pig hooves and veterinary fur. Any possible tissue damage was to assess through in histopathology of swine ears. HET-CAM results showed that all combinations can be classified as non-irritating, corroborated by the results of the histopathological evaluation of the pig's ear skin. Only the double combinations managed to remove 100% of the colony-forming units (CFU) formed on the pig's hooves. The clioquinol + terbinafine combination and the triple combination were more effective than clioquinol + ciclopirox in eradicating the preformed biofilm in fur of veterinary origin. These results show the potential of formulations of clioquinol in combination with antifungals for use in humans and in the veterinary field to combat dermatophytosis, as an important alternative therapy, for use in the near future.

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.

The clinical value of metagenomic next-generation sequencing in the microbiological diagnosis of skin and soft tissue infections

BACKGROUND

Metagenomic next-generation sequencing (mNGS), with its comprehensiveness, is widely applied in microbiological diagnosis. Etiological diagnosis is of paramount clinical importance in patients with skin and soft tissue infections (SSTIs). However, the clinical application of mNGS in SSTIs is relatively less studied.

MATERIALS AND METHODS

From April 1, 2017 to December 31, 2019, 96 SSTI cases were collected. The positive rates of pathogens detected by mNGS and culture were compared by analyzing tissue samples, pus, swabs, and/or interstitial fluids obtained from the infected parts. Modification of the antibiotic treatment strategy due to mNGS was also assessed.

RESULTS

The sensitivity of mNGS for detecting pathogens in SSTI cases was superior to that of culture testing (67.7% vs 35.4%; p < 0.01). Significantly higher identification rates for viruses (10.4% vs 0.0%; p < 0.01) and anaerobes (11.5% vs 1.0%; p < 0.01) were obtained with mNGS compared to culture. Of note, rare pathogens such as Vibrio vulnificus and Bartonella henselae were also detected by mNGS. Importantly, the proportion of multi-pathogen SSTIs detected by mNGS was higher than that of multi-pathogen SSTIs detected by culture (16.7% vs 6.3%; p = 0.035). The rate of targeted antibiotic treatment was significantly higher in mNGS-positive cases than in mNGS-negative cases (41.7% vs 3.8%; p < 0.01). In culture-negative and mNGS-positive cases, the improvement rate was higher than that in mNGS-negative cases, but this was not statistically significant (75.0% vs 73.1%; p = 0.864).

CONCLUSIONS

mNGS is a promising tool for the etiological diagnosis of SSTIs, particularly in identifying viruses, anaerobes, and multi-pathogen infections. The application of mNGS testing in clinical practice could change antibiotic treatment strategies and partly benefit clinical outcomes.

Species identification of dermatophytes isolated in China by matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry

BACKGROUND AND OBJECTIVES

Matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry (MALDI-TOF MS) is a novel technique for identifying dermatophytes. This study aimed to detect the limitation of MALDI-TOF MS applied to dermatophytes.

METHODS

A total of 113 DNA-sequenced dermatophyte isolates preserved at the Research Center for Medical Mycology of Peking University were selected for this study. Forty-two isolates were selected as reference strains used to create a supplementary database. Seventy-one isolates (Trichophyton rubrum series, T benhamiae series, T mentagrophytes series species and T schoenleinii) were used to evaluate the suitability of the MALDI-TOF MS Biotyper system. MALDI Biotyper 4.0 software was employed to construct the main spectrum profile (MSP) dendrograms.

RESULTS

Correct identification rates at the species and genus levels were 90.1% and 91.5%, respectively, using Bruker Filamentous Fungi Library 1.0 combined with the novel database. The MSP dendrogram of the T rubrum series showed unambiguous separation of T rubrum and T violaceum and that of the T benhamiae series distinguished T verrucosum, T benhamiae and T erinacei. Conversely, the MSP dendrogram of the T mentagrophytes series did not successfully distinguish T mentagrophytes, T interdigitale and T tonsurans.

CONCLUSION

MALDI-TOF MS showed good performance in the identification and delineation of the T rubrum series and T benhamiae series, but showed poor performance in T mentagrophytes series.

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.

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.

A Comparative Study on Phenotypic versus ITS-Based Molecular Identification of Dermatophytes Isolated in Dakar, Senegal

Classically, dermatophytes are identified by phenotypic methods even if these methods, sometimes, remain difficult or uncertain. On the other hand, nucleotide sequence analysis of internal transcribed spacers (ITS) of rDNA has proved to be a useful method for identification of dermatophytes. The objective of this study was to compare the phenotypic method with DNA sequencing of the ITS regions for identification of dermatophyte species isolated in Dakar, Senegal. A collection of thirty-two strains of dermatophytes were isolated from patients suffering from dermatophytosis. Mycological identification revealed Trichophyton soudanense (n = 13), T. interdigitale (n = 10), Microsporum audouinii (n = 5), and one strain for each of the following species: T. rubrum, T. mentagrophytes, and M. canis and one unidentified strain. For comparison, ITS-based PCR and DNA sequencing were applied for identification of the isolated dermatophytes. ITS sequences showed, in BLAST search analysis, 99-100% of similarity. Identification of dermatophyte isolates by conventional methods was confirmed by DNA sequencing of the ITS regions in 84% of cases. Discrepancies concern mostly T. rubrum misidentified as T. interdigitale. PCR sequencing provided an excellent tool for identifying dermatophyte strains that do not present typical morphological characteristics. It was also able to give correct identification of an atypical strain of M. audouinii responsible of mycetoma of the scalp.