PCR test for Microsporum canis identification

Antifungal activity of Carica papaya fruit extract against Microsporum canis: in vitro and in vivo study

Background

Tinea capitis (T. capitis), commonly known as scalp ringworm, is a fungal infection affecting the scalp and hair. Among the causative agents, Microsporum canis (M. canis) stands out, often transmitted from cats to humans (zoonotic disease). In this study, we investigated the efficacy of Carica papaya (C. papaya), fruit extract against dermatophytes, particularly M. canis, both in vitro and in vivo. Additionally, we aimed to identify the active compounds responsible for suppressing fungal growth and assess the toxicity of C. papaya on human cells.

Methodology

It conducted in two parts. First, In Vitro Study include the preparation of C. papaya fruit extract using methanol as the solvent, Phytochemical analysis of the plant extract including Gas chromatography-mass spectrometry (GC-MS) and Fourier-transform infrared spectroscopy (FTIR) was conducted, Cytotoxicity assays were performed using HUH-7 cells, employing the MTT assay (1-(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide), Antimicrobial activity against M. canis was evaluated, including: Zone of inhibition (ZI), Minimum inhibitory concentration (MIC), Minimum fungicidal concentration (MFC), M. canis cell alterations were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Second, In Vivo, Albino Wistar male rats were included.

Results

The phytochemical analysis of the methanolic extract from papaya revealed several functional groups, including hydroxyl, ammonia, alkane, carbonate, and alcohol. Additionally, the GC-MS analysis identified 15 compounds, with xanthosine and decanoic acid being the predominant components. The methanolic extract of papaya fruits demonstrated potent antifungal activity: ZI = 37 mm, MIC = 1,000 μg/mL, MFC = 1900 μg/mL, MTT results indicated lower cytotoxicity of the fruit extract at concentrations of 20 μg/mL, 50 μg/mL, 100 μg/mL, 150 μg/mL, and 200 μg/mL, The IC50 revealed a significant decrease in cell viability with increasing extract concentration. Notably, papaya extract induced considerable alterations in the morphology of M. canis hyphae and spores. In animal tissue, improvements were observed among the group of rats which treated with Papaya extract. This study highlights the potential of C. papaya fruits as a natural antifungal agent, warranting further exploration for clinical applications.

Expert Panel Review of Skin and Hair Dermatophytoses in an Era of Antifungal Resistance

Dermatophytoses are fungal infections of the skin, hair, and nails that affect approximately 25% of the global population. Occlusive clothing, living in a hot humid environment, poor hygiene, proximity to animals, and crowded living conditions are important risk factors. Dermatophyte infections are named for the anatomic area they infect, and include tinea corporis, cruris, capitis, barbae, faciei, pedis, and manuum. Tinea incognito describes steroid-modified tinea. In some patients, especially those who are immunosuppressed or who have a history of corticosteroid use, dermatophyte infections may spread to involve extensive skin areas, and, in rare cases, may extend to the dermis and hair follicle. Over the past decade, dermatophytoses cases not responding to standard of care therapy have been increasingly reported. These cases are especially prevalent in the Indian subcontinent, and Trichophyton indotineae has been identified as the causative species, generating concern regarding resistance to available antifungal therapies. Antifungal-resistant dermatophyte infections have been recently recognized in the United States. Antifungal resistance is now a global health concern. When feasible, mycological confirmation before starting treatment is considered best practice. To curb antifungal-resistant infections, it is necessary for physicians to maintain a high index of suspicion for resistant dermatophyte infections coupled with antifungal stewardship efforts. Furthermore, by forging partnerships with federal agencies, state and local public health agencies, professional societies, and academic institutions, dermatologists can lead efforts to prevent the spread of antifungal-resistant dermatophytes.

[Conventional and molecular diagnostics in onychomycosis-part 2 : Molecular identification of causative dermatophytes by polymerase chain reaction and sequence analysis of the internal transcribed spacer region of ribosomal DNA]

Dermatophyte identification using traditional methods such as optics-based direct fluorescence microscopy and culture is nowadays supplemented by molecular biological methods. The validity of dermatophyte DNA detection with direct uniplex-polymerase chain reaction-enzyme immunoassay (PCR-EIA) in nail samples was proven by sequence analysis of the ribosomal internal transcribed spacer (ITS) region. A total of 108 dermatophytes, isolated from patients with onychomycosis, were positive for Trichophyton rubrum (TR) and Trichophyton interdigitale (TI) in culture and/or uniplex-PCR-EIA. Conventional methods for dermatophyte identification were complemented by direct uniplex-PCR-EIA and sequence analysis of the ribosomal ITS region (18S rRNA, ITS1, 5.8S rRNA, ITS2, 28S rRNA). Of 108 patients (average age 62, median age 73), 56 showed cultural growth with 31 of them being identified as TR and 23 as TI. There was high agreement with the sequence analysis. Surprisingly, the pathogen of a single nail sample was identified as T. quinckeanum (formerly T. mentagrophytes sensu stricto), a rare zoophilic dermatophyte in Germany. A single TI strain turned out to be a misidentified T. tonsurans based on the sequence analysis. In all, 34 of the 52 specimens lacking cultural growth were detected by PCR as TR, and 18 specimens could be identified as TI. The results of dermatophyte identification of culture-negative nail samples were also in agreement with the results of sequence analysis. Molecular biological methods are well applicable, and they show high reliability for direct dermatophyte identification in nail samples without prior cultivation. Especially for nail samples without cultural growth, PCR-based dermatophyte identification was highly specific and sensitive.

In vitro virulotyping, antifungal susceptibility testing and DNA fingerprinting of Microsporum canis strains of canine and feline origin

Microsporum canis is considered the common dermatophyte agent associated with ringworm in felines and canines. In the present study, we sampled n = 548 felines and canines for the probable isolation of M. canis. The rate of isolation from the cats and dogs was 70.27 % (52/74) and 1.68 % (8/474), respectively and Persian cats were found to be highly susceptible to M. canis infection. The strains were evaluated for their production of phospholipase, lipase, catalase, and hemolysis and their ability to grow at 35 ℃. All the strains were identified as low producers of catalase and n = 17 strains exhibited high thermotolerance ability. Terbinafine was found to be the most effective antifungal drug and fluconazole was the least effective, in vitro. AFLP analysis revealed three genotypes of M. canis with 15 sub-clusters showing ≥ 90 % similarity and 7 sub-clusters exhibiting 100 % similarity. However, the phenotypic characters cannot be attributed based on the AFLP profiles.

Current Topics in Dermatophyte Classification and Clinical Diagnosis

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. Classification of many of these species has recently changed due to genetic analysis, potentially affecting clinical diagnosis and disease management. In this review, we discuss dermatophyte classification including name changes for medically important species, current and potential diagnostic techniques for detecting dermatophytes, and an in-depth review of Microsporum canis, a prevalent zoonotic dermatophyte. Fungal culture is still considered the “gold standard” for diagnosing dermatophytosis; however, modern molecular assays have overcome the main disadvantages of culture, allowing for tandem use with cultures. Further investigation into novel molecular assays for dermatophytosis is critical, especially for high-density populations where rapid diagnosis is essential for outbreak prevention. A frequently encountered dermatophyte in clinical settings is M. canis, which causes dermatophytosis in humans and cats. M. canis is adapting to its primary host (cats) as one of its mating types (MAT1-2) appears to be going extinct, leading to a loss of sexual reproduction. Investigating M. canis strains around the world can help elucidate the evolutionary trajectory of this fungi.

A new molecular marker for species-specific identification of Microsporum canis

Species identification of dermatophytes by conventional mycological methods based on macro- and microscopy analysis is time-consuming and has a lot of limitations such as slow fungal growth or low specificity. Thus, there is a need for the development of molecular methods that would provide reliable and prompt identification of this group of medically important fungi. The are many reports in the literature concerning PCR identification of dermatophyte species, but still, there are not many PCR assays for the separate detection of members of the genera Microsporum, especially Microsporum canis (zoophilic species) and Microsporum audouinii (anthropophilic species). The correct distinction of these species is important to determine the source of infection to implement the appropriate action to eliminate the path of infection transmission. In this paper, we present such a PCR-based method targeting velB gene that uses a set of two primers—Mc-VelB-F (5′-CTTCCCCACCCGCAACATC-3′) and Mc-VelB-R (5′-TGTGGCTGCACCTGAGAGTGG-3′). The amplified fragment is specific due to the presence of (CAGCAC)₈ microsatellite sequence only in the velB gene of M. canis. DNA from 153 fungal samples was used in PCR assay followed by electrophoretic analysis. The specificity of the designed set of primers was also confirmed using the online BLAST-Primer tool. The positive results were observed only in the case of M. canis isolates, and no positive results were obtained neither for other dermatophytes and non-dermatophyte fungi nor for other Eukaryotes, including the human genome sequence, as well as the representatives of bacterial and viral taxa. The developed PCR assay using the proposed Mc-VelB-F and Mc-velB-R primers can be included in the algorithm of M. canis detection in animals and humans.

Tinea corporis: an updated review

Background

Tinea corporis is a common fungal infection that mimics many other annular lesions. Physicians must familiarize themselves with this condition and its treatment.

Objective

This article aimed to provide a narrative updated review on the evaluation, diagnosis, and treatment of tinea corporis.

Methods

A PubMed search was performed with Clinical Queries using the key term ‘tinea corporis.’ The search strategy included clinical trials, meta-analyses, randomized controlled trials, observational studies, and reviews. The search was restricted to the English language. The information retrieved from the mentioned search was used in the compilation of the present article.

Results

Tinea corporis typically presents as a well-demarcated, sharply circumscribed, oval or circular, mildly erythematous, scaly patch or plaque with a raised leading edge. Mild pruritus is common. The diagnosis is often clinical but can be difficult with prior use of medications, such as calcineurin inhibitors or corticosteroids. Dermoscopy is a useful and non-invasive diagnostic tool. If necessary, the diagnosis can be confirmed by microscopic examination of potassium hydroxide wet-mount preparations of skin scrapings from the active border of the lesion. Fungal culture is the gold standard to diagnose dermatophytosis especially if the diagnosis is in doubt and results of other tests are inconclusive or the infection is widespread, severe, or resistant to treatment. The standard treatment of tinea corporis is with topical antifungals. Systemic antifungal treatment is indicated if the lesion is multiple, extensive, deep, recurrent, chronic, or unresponsive to topical antifungal treatment, or if the patient is immunodeficient.

Conclusion

The diagnosis of tinea corporis is usually clinical and should pose no problem to the physician provided the lesion is typical. However, many clinical variants of tinea corporis exist, rendering the diagnosis difficult especially with prior use of medications, such as calcineurin inhibitors or corticosteroids. As such, physicians must be familiar with this condition so that an accurate diagnosis can be made and appropriate treatment initiated.

FSH1 regulates the phenotype and pathogenicity of the pathogenic dermatophyte Microsporum canis

Microsporum canis (M. canis) is a common pathogen that causes tinea capitis and is present worldwide. The incidence of M. canis infection, particularly tinea capitis, has been increasing in China. In our previous studies, family of serine hydrolases 1 (FSH1) was identified as a potential virulence factor in tinea capitis infection caused by M. canis. To determine the function of this gene in M. canis, FSH1 was knocked down using double-stranded RNA interference mediated by Agrobacterium tumefaciens. Reverse transcription-quantitative PCR analysis was used to confirm gene knockdown. Loss of FSH1 expression by RNAi resulted in a minor phenotype alteration, but M. canis pathogenicity in guinea pig cutaneous infection was decreased compared with the wild-type strain. To the best of our knowledge, the present study is the first to demonstrate that FSH1 is associated with macroconidia septa formation and is an important contributor to M. canis virulence. These findings may advance the understanding of the function of the FSH1 gene and provide a foundation for future studies on macroconidia septa formation and pathogenicity of M. canis.

Padronização de uma PCR para diagnóstico molecular de Microsporum canis em amostras de pelos e crostas de cães e gatos

RESUMO Objetivou-se neste estudo padronizar um protocolo de reação em cadeia da polimerase (PCR) para detecção de Microsporum canis em amostras de pelos e/ou crostas de cães e gatos. Foram selecionadas 48 amostras previamente identificadas por meio de cultura. Destas, 23 foram positivas para dermatófitos no cultivo. Padronizou-se a PCR a partir de primers desenhados para o alvo M. canis. Sessenta e um por cento (14/23) das amostras positivas para dermatófitos foram identificadas como M. canis em cultura. Desse total, 71,4% (10/14) apresentaram um fragmento de 218pb compatível com o esperado para a espécie fúngica alvo dessa reação. Observou-se uma sensibilidade de 71,4% e especificidade de 100% na PCR, além de uma boa concordância entre essas técnicas de diagnóstico (Kappa: 0,78; P<0,0001). O protocolo utilizado neste estudo apresentou alta especificidade na detecção de M. canis diretamente de amostras de pelos e/ou crostas de cães e gatos, viabilizando um diagnóstico mais rápido e específico, podendo esse protocolo ser empregado como um método confirmatório para agilizar a detecção de M. canis.

Selection and validation of reference genes for qRT-PCR analysis of gene expression in Microsporum canis growing under different adhesion-inducing conditions

Dermatophytes are the group of filamentous fungi infecting keratinized structures such as skin, hair, and nails. Knowledge about genes and molecular mechanisms responsible for pathogenicity, as well as other biological properties of Microsporum canis is still relatively poor. The qRT-PCR is a reliable technique for quantifying gene expression across various biological processes, and choosing a set of suitable reference genes to normalize the expression data is a crucial step of this technique. We investigated the suitability of nine candidate reference genes: β-act, β-tub, adp-rf, ef1-α, sdha, rpl2, mbp1, psm1, and rGTPa for gene expression analysis in the dermatophyte M. canis in response to different carbon sources, phosphate levels, and pH shifts - factors that are extremely important and necessary for growth of dermatophyte in the host tissue. The transcription stability of these genes was evaluated using NormFinder, geNorm, BestKeeper, and RefFinder software. Regarding expression stability, mbp1, β-act, and sdha were the most stable housekeeping genes which we recommend for future qRT-PCR studies on M. canis strains. To the best of our knowledge this is the first study on selection and validation of reference genes for qRT-PCR data normalization in M. canis growth in culture media which promote adhesion-inducing conditions.

Diagnosis of Dermatophytosis Using Molecular Biology

Identification of fungi in dermatological samples using PCR is reliable and provides significantly improved results in comparison with cultures. It is possible to identify the infectious agent when negative results are obtained from cultures. In addition, identification of the infectious agent can be obtained in 1 day. Conventional and real-time PCR methods used for direct fungus identification in collected samples vary by DNA extraction methods, targeted DNA and primers, and the way of analysing the PCR products. The choice of a unique method in a laboratory is complicated because the results expected from skin and hair sample analysis are different from those expected in cases of onychomycosis. In skin and hair samples, one dermatophyte among about a dozen possible species has to be identified. In onychomycosis, the infectious agents are mainly Trichophyton rubrum and, to a lesser extent, Trichophyton interdigitale, but also moulds insensitive to oral treatments used for dermatophytes, which renders fungal identification mandatory. The benefits obtained with the use of PCR methods for routine analysis of dermatological samples have to be put in balance with the relative importance of getting a result in a short time, the price of molecular biology reagents and equipment, and especially the time spent conducting laboratory manipulations.

PCR and real-time PCR approaches to the identification of Arthroderma otae species Microsporum canis and Microsporum audouinii/Microsporum ferrugineum

OBJECTIVES

The identification of species in the Arthroderma otae complex is essential to determine the origin of infection and to eliminate the risk of transmission. Microsporum canis is a zoophilic species, whereas Microsporum audouinii and Microsporum ferrugineum are anthropophilic species. In this paper, we propose alternative methods that permit species-specific identification of both anthropophilic and zoophilic members of the A. otae complex METHODS: Two PCR assays were designed based on differences in the DNA fragment encoding β-tubulin and were applied in both traditional and real-time PCR using DNA isolated by rapid method from culture.

RESULT

The two assays presented in this study enable the identification of M. canis and M. audouinii/M. ferrugineum with 100% sensitivity and specificity by both traditional and real-time PCR.

CONCLUSION

We developed a new diagnostic assay using specific primers and both traditional and real-time PCR reactions that can be applied in routine laboratory praxis as well as in epidemiological studies to detect M. canis and M. audouinii/M. ferrugineum DNA from a pure culture.

Cutaneous infectious diseases: Kids are not just little people

The changes in immune response that occur with age play a significant role in disease presentation and patient management. Evolution of the innate and adaptive immune systems throughout life, influenced partly by hormonal changes associated with puberty, plays a role in the differences between pediatric and adult response to disease. We review a series of manifestations of dermatologic infectious diseases spanning bacterial, viral, and fungal origins that can be seen in both pediatric and adult age groups and highlight similarities and differences in presentation and disease course. Therapeutic options are also discussed for these infectious diseases, with particular attention to variations in management between these population subgroups, given differences in pharmacokinetics and side effect profiles.

Pathogenic fungus Microsporum canis activates the NLRP3 inflammasome

Microsporum canis is a pathogenic fungus with worldwide distribution that causes tinea capitis in animals and humans. M. canis also causes invasive infection in immunocompromised patients. To defy pathogenic fungal infection, the host innate immune system is the first line of defense. As an important arm of innate immunity, the inflammasomes are intracellular multiprotein complexes that control the activation of caspase-1, which cleaves proinflammatory cytokine pro-interleukin-1β (IL-1β) into its mature form. To determine whether the inflammasome is involved in the host defense against M. canis infection, we challenged human monocytic THP-1 cells and mouse dendritic cells with a clinical strain of M. canis isolated from patients with tinea capitis. We found that M. canis infection triggered rapid secretion of IL-1β from both THP-1 cells and mouse dendritic cells. Moreover, by using gene-specific shRNA and competitive inhibitors, we determined that M. canis-induced IL-1β secretion was dependent on NLRP3. The pathways proposed for NLRP3 inflammasome activation, namely, cathepsin B activity, K(+) efflux, and reactive oxygen species production, were all required for the inflammasome activation triggered by M. canis. Meanwhile, Syk, Dectin-1, and Card9 were found to be involved in M. canis-induced IL-1β secretion via regulation of pro-IL-1β transcription. More importantly, our data revealed that M. canis-induced production of IL-1β was dependent on the NLRP3 inflammasome in vivo. Together, this study unveils that the NLRP3 inflammasome exerts a critical role in host innate immune responses against M. canis infection, and our data suggest that diseases that result from M. canis infection might be controlled by regulating the activation of inflammasomes.