Adherence of dermatophyte microconidia and arthroconidia to human keratinocytes in vitro

Diagnosis of a recurred lesion in dermatophytosis patients after 2 weeks of antifungal therapy: A prospective observational study

Few researchers believe that various risk factors may complicate the course of dermatophytosis and/or develop various dermatoses unrelated to fungal infection at the previous lesion site. However, there is a paucity of studies that analyzed the diagnosis of lesions that recurred at the treated site of dermatophytosis.

Materials and Methods

A prospective observational study was conducted on 157 cases of dermatophytosis with positive fungal test results. A fixed dose of 100 mg of oral itraconazole once daily was administered to all patients for 2 weeks. At the end of 2 weeks, patients were assessed for clinical cure and recurrence. Recurred cases were assessed for mycological profile using a fungal test (potassium hydroxide mount and/or fungal culture) for identifying fungal infection.

Results

Only eight (5.36%) patients showed clinical cure, and 141 (94.63%) patients developed recurrence after therapy. Of the 141 cases with recurrence, only 47 (33.33%) patients were positive for fungus. Eight (5.09%) patients were lost to follow-up. Frequently encountered risk factors in the study were topical steroid use, disease in family, associated atopic dermatitis and contact with pets.

Conclusion

This is the first study that described the clinical diagnosis and mycological profile of the various lesions recurring at the previous tinea infection site in patients with dermatophytosis. Such patients presented not only with recurrent lesions of fungal infection but also developed various dermatoses unrelated to fungal infection at the sites of previous tinea infection. Various factors, which could have resulted in the observed changes, are reinfection by dermatophytes at the sites of previous tinea infection, inadequate antifungal therapy or antifungal resistance; or due to the effects of various topical steroid formulations used by the patients, such as anti-inflammatory or immunosuppressive effects or shift in immunity. Hence, diagnosis of the recurrent lesion at the site of previous dermatophytosis must be individualized and should be based on 1) duration of antifungal therapy received, 2) associated risk factors, 3) response to antifungal therapy, 4) evolution of the recurrent lesion, and/or 5) fungal tests.

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.

A Current Diagnostic and Therapeutic Challenge: Tinea Capitis

Tinea capitis is a dermatophyte scalp infection with a marked prevalence among the pediatric population. However, in the last few years, its epidemiology has changed due to increasing population migration worldwide. Host-specific and environmental factors contribute to the pathogenesis of tinea capitis. Clinically, tinea capitis may present as a subtle hair loss accompanied by scalp scaling, alopecia with scaly patches, or alopecia with black dots. A more severe form of tinea capitis is represented by kerion celsi, which clinically presents as a tender plaque covered by pustules and crusts. If left untreated, this dermatophytic infection may resolve with permanent scarring and alopecia. The pathological changes found in tinea capitis are reflected by a spectrum of clinical changes. Zoophilic infections typically prompt an extensive inflammatory reaction, while anthropophilic dermatophytoses often lack inflammation and result in more persistent lesions. Tinea capitis typically requires systemic antifungal therapy. Griseofulvin, terbinafine, itraconazole, and fluconazole are the main antifungal agents used. Currently, the duration of antifungal therapy varies based on the clinical presentation and type of dermatophyte involved. Through the reported cases and literature review, we aim to emphasize the importance of the early recognition of atypical variants of tinea capitis in immunocompetent children for the prompt initiation of systemic antifungal therapy, minimizing the need for prolonged treatment. Additionally, we emphasize the importance of regular laboratory testing during systemic antifungal therapy, particularly liver enzyme tests, to prevent adverse events, especially in cases requiring long-term treatment.

Angioinvasive Trichophyton rubrum associated necrotizing fasciitis in an immunocompromised patient

Angioinvasive dermatophytosis with necrotizing fasciitis can be a rare complication in immunocompromised patients with early surgical debridement, 12 weeks of oral terbinafine, and reduction in immunosuppression being a viable management strategy.

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.

Towards a Standardized Procedure for the Production of Infective Spores to Study the Pathogenesis of Dermatophytosis

Dermatophytoses are superficial infections of human and animal keratinized tissues caused by filamentous fungi named dermatophytes. Because of a high and increasing incidence, as well as the emergence of antifungal resistance, a better understanding of mechanisms involved in adhesion and invasion by dermatophytes is required for the further development of new therapeutic strategies. In the last years, several in vitro and in vivo models have emerged to study dermatophytosis pathogenesis. However, the procedures used for the growth of fungi are quite different, leading to a highly variable composition of inoculum for these models (microconidia, arthroconidia, hyphae), thus rendering difficult the global interpretation of observations. We hereby optimized growth conditions, including medium, temperature, atmosphere, and duration of culture, to improve the sporulation and viability and to favour the production of arthroconidia of several dermatophyte species, including Trichophyton rubrum and Trichophyton benhamiae. The resulting suspensions were then used as inoculum to infect reconstructed human epidermis in order to validate their ability to adhere to and to invade host tissues. By this way, this paper provides recommendations for dermatophytes culture and paves the way towards a standardized procedure for the production of infective spores usable in in vitro and in vivo experimental models.

Molecular epidemiology of Tinea gladiatorum in contact sports in northern Iran

BACKGROUND

Tinea gladiatorum as the major health concern among combat athletes and the most common cause of a decrease in the quality of their sports activities.

OBJECTIVES

This study aimed to determine the molecular epidemiology of tinea gladiatorum in contact sports in Mazandaran Province, Northern Iran.

MATERIALS/METHODS

In total, 631 suspected athletes out of 4240 ones were screened for tinea gladiatorum in this cross-sectional study from May 2018 to February 2019. The infection was confirmed by direct microscopy and culture tests. The causative agents were identified by polymerase chain reaction-restriction fragment length polymorphism method on ITS rDNA region. The indoor environmental factors were evaluated in 81 sports halls in terms of temperature (°C), humidity (%), density (m² /athletes) and the number of ventilators.

RESULTS

Tinea gladiatorum was confirmed in 6.5% (278/4240) of the athletes. Tinea corporis was the most common type of tinea (192/278; 69.0%), and 175 cases (27.7%) had more than one type of tinea. Moreover, Trichophyton tonsurans (192/203; 94.5%) was the most aetiological agent in all athletes followed by Microsporum canis (6/203; 2.9%), Trichophyton rubrum (2/203; 0.9%) and Trichophyton interdigitale (1/203; 0.4%). There was no significant association between the prevalence of tinea gladiatorum and the indoor environmental factors.

CONCLUSION

T. tonsurans is the most common agent of tinea gladiatorum in Northern Iran. Since no positive culture of dermatophyte was obtained from mats, it seems that skin-to-skin contact would be the most probable mode of transmission among wrestlers. Accordingly, periodical checkups should be considered by health care providers.

Evaluation of an Explanted Porcine Skin Model to Investigate Infection with the Dermatophyte Trichophyton rubrum

Dermatophytosis is a fungal infection of skin, hair and nails, and the most frequently found causative agent is Trichophyton rubrum. The disease is very common and often recurring, and it is therefore difficult to eradicate. To develop and test novel treatments, infection models that are representative of the infection process are desirable. Several infection models have been developed, including the use of cultured cells, isolated corneocytes, explanted human skin or reconstituted human epidermis. However, these have various disadvantages, ranging from not being an accurate reflection of the site of infection, as is the case with, for example, cultured cells, to being difficult to scale up or having ethical issues (e.g., explanted human skin). We therefore sought to develop an infection model using explanted porcine skin, which is low cost and ethically neutral. We show that in our model, fungal growth is dependent on the presence of skin, and adherence of conidia is time-dependent with maximum adherence observed after ~ 2 h. Scanning electron microscopy suggested the production of fibril-like material that links conidia to each other and to skin. Prolonged incubation of infected skin leads to luxurious growth and invasion of the dermis, which is not surprising as the skin is not maintained in conditions to keep the tissue alive, and therefore is likely to lack an active immune system that would limit fungal growth. Therefore, the model developed seems useful to study the early stages of infection. Furthermore, we demonstrate that the model can be used to test novel treatment regimens for tinea infections.

In vitro models of dermatophyte infection to investigate epidermal barrier alterations

Fungal infections of the skin, known as dermatophytoses, are initiated at the epidermal barrier and lead to dysfunctions of the stratum corneum and cornified skin appendages. Dermatophytosis affects a significant part of the human population and, despite the availability of effective treatments, its prevalence is still increasing. Numerous dermatophyte species are able to induce lesions in both animals and humans, with different clinical pictures and host inflammatory responses. The understanding of the infectious process and of tissue responses has been impeded by discrepancies between observations in vivo or in research models. Indeed, cells cultured as monolayers do not undergo the keratinization process required to study the adherence and invasion of dermatophytes. Animal models lack relevance to study human dermatophytosis because of species-specific differences in the development of lesions and inflammatory responses. This review focuses on the recent development of cultured human skin equivalents, which partly overcomes those limitations and allows improved understanding of the pathogenesis of dermatophytosis in human being, especially the impacts of infection on epidermal barrier integrity.

Host- and pathogen-dependent susceptibility and predisposition to dermatophytosis

Dermatophytes are a highly specialized group of keratinophilic and keratinolytic filamentous fungi causing a ringworm disease called dermatophytosis or superficial mycoses. Although dermatophyte infections do not threaten the host's life, they lower its quality in humans by causing discomfort related to cosmetic problems and through their epidemiological significance, whereas in farm animals they are responsible for economic losses and constitute a source of the spread of spores. Evidence from countless observational studies that have been conducted over the last 90 years indicates that dermatophytes infect humans of every age, race, gender and socioeconomic status with strikingly high rates, as well as both farmed and wild animals in various health conditions and with various epidemiological statuses. However, the prevalence of superficial fungal infections is highly variable, since it depends on several parameters associated with the infected individual and the dermatophyte, their mutual interactions, and epidemiological and geographical factors. The curious disparity in dermatophyte infection patterns has prompted many investigators to search for a link between the host, the host's predispositions and susceptibility to the disease, and the dermatophyte species and virulence. Thus, the question arises as to whether, in addition to the generally recognized factors predisposing hosts to diseases, there are some other predispositions to dermatophyte infections in a species-specific host. In this review, we describe recent findings about the mechanism of dermatophyte infections, focusing on the adaptation of the fungi to the host and conditions predisposing each side to the disease.

A "Hole Punched Plate" method for easy generation and harvesting of microconidia in the dermatophyte Trichophyton rubrum

Handling of the medically important dermatophyte Trichophyton rubrum in the laboratory typically requires the generation of spores — for storage, treatment and plating when needed. The described method allows technically simple but efficient generation and harvesting of microconidia by cutting holes in Sabouraud dextrose agar medium that is covered by a mature T. rubrum mycelium.

Modeling dermatophytosis in reconstructed human epidermis: A new tool to study infection mechanisms and to test antifungal agents

Dermatophytosis is a superficial fungal infection of keratinized structures that exhibits an increasing prevalence in humans and is thus requesting novel prophylactic strategies and therapies. However, precise mechanisms used by dermatophytes to adhere at the surface of the human epidermis and invade its stratum corneum are still incompletely identified, as well as the responses provided by the underlying living keratinocytes during the infection. We hereby report development of an in vitro model of human dermatophytosis through infection of reconstructed human epidermis (RHE) by arthroconidia of the anthropophilic Trichophyton rubrum species or of the zoophilic Microsporum canis and Arthroderma benhamiae species. By modulating density of arthroconidia in the inoculum and duration of exposure to such pathogens, fungal infection limited to the stratum corneum was obtained, mimicking severe but typical in vivo situation. Fungal elements in infected RHE were monitored over time by histochemical analysis using periodic-acid Schiff-staining or quantified by qPCR-detection of fungal genes inside RHE lysates. This model brings improvements to available ones, dedicated to better understand how dermatophytes and epidermis interact, as well as to evaluate preventive and therapeutic agents. Indeed, miconazole topically added to RHE was demonstrated to inhibit fungal infection in this model.

Diagnosis and treatment of dermatophytosis in dogs and cats.: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology

BACKGROUND

Dermatophytosis is a superficial fungal skin disease of cats and dogs. The most common pathogens of small animals belong to the genera Microsporum and Trichophyton. It is an important skin disease because it is contagious, infectious and can be transmitted to people.

OBJECTIVES

The objective of this document is to review the existing literature and provide consensus recommendations for veterinary clinicians and lay people on the diagnosis and treatment of dermatophytosis in cats and dogs.

METHODS

The authors served as a Guideline Panel (GP) and reviewed the literature available prior to September 2016. The GP prepared a detailed literature review and made recommendations on selected topics. The World Association of Veterinary Dermatology (WAVD) provided guidance and oversight for this process. A draft of the document was presented at the 8th World Congress of Veterinary Dermatology (May 2016) and was then made available via the World Wide Web to the member organizations of the WAVD for a period of three months. Comments were solicited and posted to the GP electronically. Responses were incorporated by the GP into the final document.

CONCLUSIONS

No one diagnostic test was identified as the gold standard. Successful treatment requires concurrent use of systemic oral antifungals and topical disinfection of the hair coat. Wood's lamp and direct examinations have good positive and negative predictability, systemic antifungal drugs have a wide margin of safety and physical cleaning is most important for decontamination of the exposed environments. Finally, serious complications of animal-human transmission are exceedingly rare.

Quantitative and structural analyses of the in vitro and ex vivo biofilm-forming ability of dermatophytes

PURPOSE

The aim of this study was to evaluate the in vitro and ex vivo biofilm-forming ability of dermatophytes on a nail fragment.

METHODOLOGY

Initially, four isolates of Trichophyton rubrum, six of Trichophyton tonsurans, three of Trichophyton mentagrophytes, ten of Microsporum canis and three of Microsporum gypseum were tested for production biomass by crystal violet assay. Then, one strain per species presenting the best biofilm production was chosen for further studies by optical microscopy (Congo red staining), confocal laser scanning (LIVE/DEAD staining) and scanning electron (secondary electron) microscopy.

RESULTS

Biomass quantification by crystal violet assay, optical microscope images of Congo red staining, confocal microscope and scanning electron microscope images revealed that all species studied are able to form biofilms both in vitro and ex vivo, with variable density and architecture. M. gypseum, T. rubrum and T. tonsurans produced robust biofilms, with abundant matrix and biomass, while M. canis produced the weakest biofilms compared to other species.

CONCLUSION

This study sheds light on biofilms of different dermatophyte species, which will contribute to a better understanding of the pathophysiology of dermatophytosis. Further studies of this type are necessary to investigate the processes involved in the formation and composition of dermatophyte biofilms.

Fungi Isolated From House Flies (Diptera: Muscidae) on Penned Cattle in South Texas

Musca domestica L. were collected from cattle diagnosed with bovine ringworm to evaluate the potential of the house fly to disseminate Trichophyton verrucosum E. Bodin, a fungal dermatophyte that is the causative agent for ringworm in cattle. Fungal isolates were cultured from 45 individual flies on supplemented Sabouraud dextrose agar, and isolates were identified using morphological and microscopic approaches. Each isolate was identified further by PCR amplification of the ribosomal DNA locus with fungal-specific primers and subsequent amplicon sequencing. Trichophyton verrucosum was not identified using these approaches. However, 35 different fungal species representing 17 genera were cultured from collected flies, including several species that are allergenic and pathogenic to humans and animals. Several species within the fungal orders Hypocreales, Microascales, Onygenales, Saccharomycetales, Xylaniales, and Agaricales were observed for the first time on house flies. The most frequent fungus recovered was Cladosporium cladosporoides Fresen, which is known to be a ubiquitous, airborne allergen to humans.

Tinea Capitis: Current Status

Tinea capitis remains a common childhood infection in many parts of the world. Yet knowledge of the underlying pathogenetic mechanisms and the development of effective immunity have shown striking advances, and new methods of diagnosis ranging from dermoscopy to molecular laboratory tests have been developed even though they have not been assimilated into routine practice in many centres. Treatment is effective although it needs to be given for at least 1 month. What is missing, however, is a systematic approach to control through case ascertainment and therapy.

Genetic Predictors of Susceptibility to Dermatophytoses

Countless observational studies conducted over the last century reveal that dermatophytes infect humans of every age, race, gender, and socioeconomic status with strikingly high rates. The curious disparity in dermatophyte infection patterns observed within and between populations has led countless investigators to explore whether genetics underlie a susceptibility to, or confer protection against, dermatophyte infections. This paper examines the data that offer a link between genetics and dermatophytoses and discusses the underlying mechanisms that support these observations.

Photodynamic therapy as an antifungal treatment

Photodynamic therapy (PDT) involves the systemic or topical application of a photosensitizer (PS), alongside the selective illumination of the target lesion with light of an appropriate wavelength, in order to promote localized oxidative photodamage and subsequent cell death. Numerous studies have demonstrated that PDT is highly effective in the destruction of fungi in vitro. The mechanism underlying the effects of PDT results from the photons of visible light of an appropriate wavelength interacting with the intracellular molecules of the PS. Reactive species are produced as a result of the oxidative stress caused by the interaction between the visible light and the biological tissue. At present, no antifungal treatment based on PDT has been licensed. However, antifungal PDT is emerging as an area of interest for research.

Severe Dermatophytosis and Acquired or Innate Immunodeficiency: A Review

Dermatophytes are keratinophilic fungi responsible for benign and common forms of infection worldwide. However, they can lead to rare and severe diseases in immunocompromised patients. Severe forms include extensive and/or invasive dermatophytosis, i.e., deep dermatophytosis and Majocchi’s granuloma. They are reported in immunocompromised hosts with primary (autosomal recessive CARD9 deficiency) or acquired (solid organ transplantation, autoimmune diseases requiring immunosuppressive treatments, HIV infection) immunodeficiencies. The clinical manifestations of the infection are not specific. Lymph node and organ involvement may also occur. Diagnosis requires both mycological and histological findings. There is no consensus on treatment. Systemic antifungal agents such as terbinafine and azoles (itraconazole or posaconazole) are effective. However, long-term outcome and treatment management depend on the site and extent of the infection and the nature of the underlying immunodeficiency.

Sacha Inchi Oil (Plukenetia volubilis L.), effect on adherence of Staphylococus aureus to human skin explant and keratinocytes in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Plukenetia volubilis L. (Euphorbiaceae) is a domesticated vine distributed from the high-altitude Andean rain forest to the lowlands of the Peruvian Amazon. Oil from the cold-pressed seeds, sold under the commercial name of Sacha Inchi Oil (SIO) is actually much in favour because it contains a high percentage of omega 3 and omega 6, and is hence used as a dietary supplement. SIO is also used traditionally for skin care, in order to maintain skin softness, and for the treatment of wounds, insect bites and skin infections, in a tropical context where the skin is frequently damaged.

AIMS OF THE STUDY

This study was designed in order to verify whether the traditional use of SIO for skin care would have any impact on Staphylococcus aureus growth and skin adherence, as S. aureus is involved in many skin pathologies (impetigo, folliculitis, furuncles and subcutaneous abscesses) being one if the main pathogens that can be found on the skin. Therefore, our objective was to assess SIO bactericidal activity and interference with adherence to human skin explants and the keratinocyte cell line. Cytotoxicity on that cells was also determined. The activity of SIO was compared to coconut oil (CocO), which is widely used for skin care but has different unsaturated fatty acids contents.

MATERIALS AND METHODS

Laboratory testing with certified oil, determined antibacterial activity against radio labelled S. aureus. Cytotoxic effects were measured with XTT on keratinocyte cells and with neutral red on human skin explants; phenol was used as cytotoxic control. Adherence assays were carried out by mixing H3-labelled S. aureus bacteria with keratinocyte cells and human skin explants, incubated with oils 2h before (to determine the inhibition of adherence, assimilated to a preventive effect) or 2h after the contact of the biological material with S. aureus (to assess the detachment of the bacteria, assimilated to a curative effect). Residual radioactivity measured after washings made it possible to determine the adherence intensity. Bactericidal effect was determined by colony counting on trypticase soy agar.

RESULTS

Laboratory assays showed that SIO and CocO, tested undiluted, were not cytotoxic on keratinocytes nor human explants and were not bactericidal neither. SIO was more active as antiadherent (preventive) than CocO on keratinocytes. There was no significant difference between detachment effects (curative) of both oils on keratinocytes but SIO was almost 5 times more active on the detachment of S. aureus from human skin explants.

CONCLUSION

From that study it can be concluded that the use of SIO on dermal cells is safe and efficient in the inhibition of S. aureus adherence. Our results tend to support the traditional use of undiluted SIO in skin care.

Effective Single Photodynamic Treatment of ex Vivo Onychomycosis Using a Multifunctional Porphyrin Photosensitizer and Green Light

Onychomycosis is predominantly caused by the dermatophytes Trichophyton rubrum, Trichophyton mentagrophytes and Trichophyton tonsurans. The main treatment obstacle concerns low nail-plate drug permeability. In vitro antifungal photodynamic treatment (PDT) and nail penetration enhancing effectiveness have been proven for multifunctional photosensitizer 5,10,15-tris(4-N-methylpyridinium)-20-(4-(butyramido-methylcysteinyl)-hydroxyphenyl)-[21H,23H]-porphine trichloride (PORTHE). This study investigates single PORTHE green laser/LED PDT of varying degrees of ex vivo onychomycoses in a human nail model. T. mentagrophytes, T. rubrum, T. tonsurans onychomycoses were ex vivo induced on nail pieces at 28 °C (normal air) and 37 °C (6.4% CO₂) during 3 to 35 days and PDTs applied to the 37 °C infections. All dermatophytes showed increasingly nail plate invasion at 37 °C between 7 and 35 days; arthroconidia were observed after 35 days for T. mentagrophytes and T. tonsurans. Using 81 J/cm² (532 nm) 7-day T. mentagrophytes onychomycoses were cured (92%) with 80 µM PORTHE (pH 8) after 24 h propylene glycol (PG, 40%) pre-treatment and 35-day onychomycoses (52%–67%) with 24 h PORTHE (40–80 µM)/40% PG treatment (pH 5). 28 J/cm² LED light (525 ± 37 nm) improved cure rates to 72%, 83% and 73% for, respectively, T. mentagrophytus, T. rubrum and T. tonsurans 35-day onychomycoses and to 100% after double PDT. Data indicate PDT relevance for onychomycosis.

Dermatophytosis diagnosed at the Evandro Chagas Institute, Pará, Brazil

Dermatophytosis is caused by a dermatophyte fungus that affects the stratum corneum and keratinized tissue. Dermatophyte fungus has been reported worldwide as the causative agent of dermatophytosis, but the etio-epidemiological aspects of these mycoses in the state of Pará remain unknown. The purpose of this study was to describe the etio-epidemiological profile of dermatophytosis diagnosed in patients at the Evandro Chagas Institute from May 2005 to June 2006. A total of 494 patients were admitted, and their samples were collected, submitted for direct microscopic examination using 20% KOH and cultured in Sabouraud and Mycosel medium. The identification was based in macro and microscopic characteristics. Direct examinations were positive in 13% (66/494) of the patients, and agent isolation by cultivation of the biological sample was successful in 4% (20/494), with a high prevalence of T. mentagrophytes (40%; 8/20). Dermatophytosis was more frequent in women (58%; 38/66). Fifty-two percent (21/38) of the cases were children with an average age of 8 years. The most frequent clinical presentation was Tinea corporis (55%, 36/66). For the cases in which the dermatophyte agent was not isolated, we discuss the factors that may be interfering with isolation. Tinea corporis occurred more frequently observed when T. mentagrophytes and T. rubrum were the major etiologic agents.

Mechanisms of skin adherence and invasion by dermatophytes

Dermatophytes are keratinophilic fungi that can be pathogenic for humans and animals by infecting the stratum corneum, nails, claws or hair. The first infection step consists of adherence of arthroconidia to the stratum corneum. The mechanisms and the kinetics of adherence have been investigated using different in vitro and ex vivo experimental models, most notably showing the role of a secreted serine protease from Microsporum canis in fungal adherence to feline corneocytes. After germination of the arthroconidia, dermatophytes invade keratinised structures that have to be digested into short peptides and amino acids to be assimilated. Although many proteases, including keratinolytic ones, have been characterised, the understanding of dermatophyte invasion mechanisms remains speculative. To date, research on mechanisms of dermatophyte infection focused mainly on both secreted endoproteases and exoproteases, but their precise role in both fungal adherence and skin invasion should be further explored.

Growth Inhibition and Morphological Alterations of Trichophyton Rubrum Induced by Essential oil from Cymbopogon Winterianus Jowitt Ex Bor

Trichophyton rubrum is one of the most common fungi causer of dermatophytosis, mycosis that affect humans and animals around the world. Researches aiming new products with antifungal activity become necessary to overcome difficulties on treatment of these infections. Accordingly, this study aimed to investigate the antifungal activity of essential oil from Cymbopogon winterianus against the dermatophyte T. rubrum. The antifungal screening was performed by solid medium diffusion method with 16 T. rubrum strains, minimum inhibitory concentration (MIC) and minimum fungicide concentration (MFC) were determined using the microdilution method. The effects on mycelial dry weight and morphology were also observed. Screening showed essential oil in natura inhibited all the tested strains, with inhibition zones between 24-28 mm diameter. MIC50 and MIC90 values of the essential oil were 312 μg/mL for nearly all the essayed strains (93.75 %) while the MFC50 and MFC90 values were about eight times higher than MIC for all tested strains. All tested essential oil concentrations managed to inhibit strongly the mycelium development. Main morphological changes on the fungal strains observed under light microscopy, which were provided by the essential oil include loss of conidiation, alterations concerning form and pigmentation of hyphae. In the oil presence, colonies showed folds, cream color and slightly darker than the control, pigment production was absent on the reverse and with evident folds. It is concluded that C. winterianus essential oil showed activity against T. rubrum. Therefore, it could be known as potential antifungal compound especially for protection against dermatophytosis.

Dermatomycosis: Conditions that contribute to the disease development

Skin lesions caused by dermatophytes are classified depending on the infected skin structure: surface layer of cutis, fur layer, clutches or nails. Surface mycoses are caused by dermatophytes: Epidermophyton, Microsporum and Trichophyton species (also important are Malassezia spp., Candida spp., and Trichosporon). Skin is the target tissue for fungal infections if the epithelial layer is damaged and immune system cannot cope with the infection, or if the conditions are favorable for dermatophytes, which spread in the cutis due to the enzyme activities. Dermatophytes can be found on skin surface if they contaminate or colonize epidermis or hair follicles. However, clinical symptoms of lesion on the skin are sometimes absent. According to the literature data 6-9% of skin lesions are caused by dermatophyte in human medicine. Similar situation is in veterinary medicine. Fungus that cause dermatomycosis are widespread in the nature and could be divided into: zoophilic, geophilic and anthrophilic. The goal of this paper is to present the latest knowledge in pathogenesis on dermatomycosis, predisposing factors important for the outcome of the disease, and immunological reaction of organism to the fungal infection. Our intention is to summarize the subject and present the facts related to specific problems in dermatomycosis.

The susceptibility of dermatophytes to photodynamic treatment with special focus on Trichophyton rubrum

Owing to the accessibility of skin to light, many applications of photodynamic treatment (PDT) have been developed within dermatology. The recent increase of dermatological antimicrobial PDT investigations is related to the growing problem of bacterial and fungal resistance to antibiotics. This review focuses on the susceptibility of dermatophytic fungi, in particular Trichophyton rubrum, to PDT and shows its potential usefulness in treatment of clinical dermatophytoses. There are no data indicating significant differences in PDT susceptibility between various dermatophytes and it is unlikely that treatment problems of especially T. rubrum with current antimycotics would occur in case of PDT. Red light 5-aminolevulinic acid-mediated PDT is after repeated sessions successful in in vivo treatment of onychomycosis (fungal nail infection) caused by various dermatophytes. Regarding skin dermatophytoses, UVA-1 PDT with cationic porphyrins appears to be safe and efficient. Most effective toward T. rubrum ex vivo is 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) when combined with UVA-1 radiation or red light; this creates the possibility of efficiently treating nail infections and remaining spores in hair follicles. If the promising in vitro and ex vivo results could be transferred to clinical practice, then PDT has a good prospect to become a worthy alternative to established antifungal drugs.

Preclinical studies with 5,10,15-Tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride for the photodynamic treatment of superficial mycoses caused by Trichophyton rubrum

Dermatophytes are fungi that cause infections of keratinized tissues. We have recently demonstrated the susceptibility of the dermatophyte Trichophyton rubrum to photodynamic treatment (PDT) with 5,10,15-Tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) in 5 mm citric acid/sodium citrate buffer (pH 5.2, formulation I). In this work, we examined the penetration of Sylsens B in healthy and with T. rubrum infected skin and we investigated the susceptibility of T. rubrum to PDT using formulation I and UVA-1 radiation (340-550 nm). Skin penetration studies were performed with formulations I and II (Sylsens B in PBS, pH 7.4) applied on dermatomed skin, human stratum corneum (SC), disrupted SC by T. rubrum growth and SC pretreated with a detergent. No penetration was observed in healthy skin. Disruption of SC by preceding fungal growth caused Sylsens B penetration at pH 7.4, but not at pH 5.2. However, chemically damaged SC allowed Sylsens B to penetrate also at pH 5.2. UVA-1 PDT was applied ex vivo during two fungal growth stages of two T. rubrum strains (CBS 304.60 and a clinical isolate). Both strains could be killed by UVA-1 alone (40 J/cm(2)). Combined with formulation I (1 and 10 microm Sylsens B for, respectively, CBS 304.60 and the clinical isolate), only 18 J/cm(2) UVA-1 was required for fungal kill. Therefore, PDT with 10 microm Sylsens B (formulation I) and 18 J/cm(2) UVA-1 could be considered as effective and safe. This offers the possibility to perform clinical studies in future.

Secreted subtilisins of Microsporum canis are involved in adherence of arthroconidia to feline corneocytes

Microsporum canis is a pathogenic fungus that causes a superficial cutaneous infection called dermatophytosis, mainly in cats and humans. The mechanisms involved in adherence of M. canis to epidermis have never been investigated. Here, a model was developed to study the adherence of M. canis to feline corneocytes through the use of a reconstructed interfollicular feline epidermis (RFE). In this model, adherence of arthroconidia to RFE was found to be time-dependent, starting at 2 h post-inoculation and still increasing at 6 h. Chymostatin, a serine protease inhibitor, inhibited M. canis adherence to RFE by 53%. Moreover, two mAbs against the keratinolytic protease subtilisin 3 (Sub3) inhibited M. canis adherence to RFE by 23%, suggesting that subtilisins, and Sub3 in particular, are involved in the adherence process.

Pathogenesis of dermatophytosis

Despite the superficial localization of most dermatophytosis, host-fungus relationship in these infections is complex and still poorly elucidated. Though many efforts have been accomplished to characterize secreted dermatophytic proteases at the molecular level, only punctual insights have been afforded into other aspects of the pathogenesis of dermatophytosis, such as fungal adhesion, regulation of gene expression during the infection process, and immunomodulation by fungal factors. However, new genetic tools were recently developed, allowing a more rapid and high-throughput functional investigation of dermatophyte genes and the identification of new putative virulence factors. In addition, sophisticated in vitro infection models are now used and will open the way to a more comprehensive view of the interactions between these fungi and host epidermal cells, especially keratinocytes.

Infection stages of the dermatophyte pathogen Trichophyton: microscopic characterization and proteolytic enzymes

Dermatophytes are pathogenic fungi that infect human skin, nails and hair and cause dermatophytosis. Trichophyton mentagrophytes is one of the most widespread species that belong to this group. Infection of the skin tissues include several stages, i.e., adhesion to the surface of the skin, invasion into the sublayers by the penetration of fungal elements and secretion of enzymes that degrade the skin components. In this study we have followed the morphology of the fungal elements, such as arthroconidia and hyphae, during the adhesion and invasion stages. Skin explants were inoculated with the dermatophyte and observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Skin explants were also inoculated with a transgenic isolate of T. mentagrophytes expressing the green fluorescent protein (GFP). The infected sublayers were investigated by confocal scanning laser microscopy (CSLM). As an adaptation to the tissue environment, the dermatophyte produced long fibrils when it is on the open surface of the stratum corneum, while short and thin fibrils are produced inside the dense sublayers. The short and long projections might have a role in adhesion. Invasion may be produced by mechanical and biochemical means. Invasion of the tissue showed hyphal branching and growth in multiple directions. The proteolytic profile was assayed by substrate gel and proteolytic activity. Two serine proteases of similar molecular weight were secreted during growth on the epidermal matrix components keratin and elastin. The dermatophyte may use the proteolytic enzymes to invade the surface and also the deep layer of the skin in immunocompromised patients. Dermatophytes, which are well adapted infectious agents, seem to use their mechanical and biochemical capabilities to invade the skin tissue effectively.

Reconstructed interfollicular feline epidermis as a model for Microsporum canis dermatophytosis

Microsporum canis is a pathogenic fungus that causes a superficial cutaneous infection called dermatophytosis. The complexity of mechanisms involved in dermatophytic infections makes relevant in vivo studies particularly difficult to perform. The aim of this study was to develop a new in vitro model of M. canis dermatophytosis using feline fetal keratinocytes in reconstructed interfollicular epidermis, and to investigate its relevance in studying the host-pathogen relationship. Histological analysis of reconstructed interfollicular feline epidermis (RFE) revealed a fully differentiated epidermis. A proliferation assay showed replicating cells only in the basal layer, indicating that RFE is a well-stratified living tissue, leading to the formation of a horny layer. Histopathological analysis of RFE infected by M. canis arthroconidia revealed that the fungus invades the stratum corneum and produces SUB3, a keratinase implicated in the infectious process. In view of these results, an M. canis dermatophytosis model on RFE seems to be a useful tool to investigate mechanisms involved in natural M. canis feline infections.

The use of global transcriptional analysis to reveal the biological and cellular events involved in distinct development phases of Trichophyton rubrum conidial germination

Background

Conidia are considered to be the primary cause of infections by Trichophyton rubrum.

Results

We have developed a cDNA microarray containing 10250 ESTs to monitor the transcriptional strategy of conidial germination. A total of 1561 genes that had their expression levels specially altered in the process were obtained and hierarchically clustered with respect to their expression profiles. By functional analysis, we provided a global view of an important biological system related to conidial germination, including characterization of the pattern of gene expression at sequential developmental phases, and changes of gene expression profiles corresponding to morphological transitions. We matched the EST sequences to GO terms in the Saccharomyces Genome Database (SGD). A number of homologues of Saccharomyces cerevisiae genes related to signalling pathways and some important cellular processes were found to be involved in T. rubrum germination. These genes and signalling pathways may play roles in distinct steps, such as activating conidial germination, maintenance of isotropic growth, establishment of cell polarity and morphological transitions.

Conclusion

Our results may provide insights into molecular mechanisms of conidial germination at the cell level, and may enhance our understanding of regulation of gene expression related to the morphological construction of T. rubrum.

A novel ex vivo skin model to study the susceptibility of the dermatophyte Trichophyton rubrum to photodynamic treatment in different growth phases

BACKGROUND

Dermatophytes are fungi that can cause infections of skin, hair and nails because of their ability to feed on keratin. Superficial mycoses are among the most prevalent infectious diseases worldwide. Two important restrictions of current therapeutic options are the recurrence of the infection and prolonged treatment. This is especially true for infections caused by Trichophyton rubrum, a widely distributed dermatophyte. The application of photosensitizers for treatment of fungal infections is, within the field of photodynamic treatment (PDT), relatively new. Recently, we demonstrated that the porphyrins 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) and deuteroporphyrin monomethylester (DP mme) were excellent photosensitizers towards T. rubrum when using red light.

OBJECTIVES AND METHODS

To evaluate the photodynamic effectiveness of the porphyrins in a situation that mimics the clinical situation, we developed an ex vivo model using human stratum corneum. This model offers the possibility of applying PDT at different time points during the germination and subsequent development of T. rubrum microconidia. The model was used for two different incubation media, Dulbecco's modified Eagle medium (DMEM) and distilled water.

RESULTS AND CONCLUSIONS

We demonstrated that the PDT susceptibility of T. rubrum depended on the time of PDT application after spore inoculation. A decrease in susceptibility was observed with increasing time of PDT application for both photosensitizers in DMEM. Changing the incubation medium to distilled water resulted in an increased fungicidal effect for Sylsens B and in a decreased effect for DP mme. We conclude that T. rubrum is susceptible to PDT in a situation that mimics the clinical situation. The fungicidal effect of PDT on fungal spores is of particular importance.

Green fluorescent protein (GFP) as a vital marker for pathogenic development of the dermatophyte Trichophyton mentagrophytes

Skin infections by dermatophytes of the genus Trichophyton are widespread, but methods to investigate the molecular basis of pathogenicity are only starting to be developed. The initial stages of growth on the host can only be studied by electron microscopy, which requires fixing the tissue. This paper shows that restriction-enzyme-mediated integration (REMI) provides stable expression of the green fluorescent protein (GFP) in a clinical isolate of Trichophyton mentagrophytes. Under control of a constitutively active fungal promoter, GFP renders the hyphae fluorescent both in culture and in a recently developed model using human skin explants. Stages of infection and penetration into the skin layers were visualized by confocal microscopy. The stages of infection can thus be followed using GFP as a vital marker, and this method will also provide, for the first time, a means to follow gene expression during infection of skin by dermatophyte fungi.

Isolation of a Microsporum canis gene family encoding three subtilisin-like proteases expressed in vivo

Microsporum canis is the main agent of dermatophytosis in dogs and cats and is responsible for frequent zoonosis. The pathogenesis of the disease remains largely unknown, however. Among potential fungal virulence factors are secreted keratinolytic proteases, whose molecular characterization would be an important step towards the understanding of dermatophytic infection pathogenesis. M. canis secretes a 31.5 kDa keratinolytic subtilisin-like protease as the major component in a culture medium containing cat keratin as the sole nitrogen source. Using a probe corresponding to a gene's internal fragment, which was obtained by polymerase chain reaction, the entire gene encoding this protease named SUB3 was cloned from a M. canislambdaEMBL3 genomic library. Two closely related genes, termed SUB1 and SUB2, were also cloned from the library using as a probe the gene coding for Aspergillus fumigatus 33 kDa alkaline protease (ALP). Deduced amino acid sequence analysis revealed that SUB1, SUB2, and SUB3 are secreted proteases and show large regions of identity between themselves and with subtilisin-like proteases of other filamentous fungi. Interest ingly, mRNA of SUB1, SUB2, and SUB3 were detected by reverse transcriptase nested-polymerase chain reaction from hair of experimentally infected guinea pigs. These results show that SUB1, SUB2, and SUB3 encode a family of subtilisin-like proteases and strongly suggest that these proteases are produced by M. canis during the invasion of keratinized structures. This is the first report describing the isolation of a gene family encoding potential virulence-related factors in dermatophytes.