EPIDEMIOLOGY OF THE DERMATOPHYTOSES SOURCES OF INFECTION, MODES OF TRANSMISSION AND EPIDEMICITY

Survey on Dermatophytes Isolated from Animals in Switzerland in the Context of the Prevention of Zoonotic Dermatophytosis

Most inflammatory dermatophytoses in humans are caused by zoophilic and geophilic dermatophytes. Knowledge of the epidemiology of these fungi in animals facilitates the prevention of dermatophytosis of animal origin in humans. We studied the prevalence of dermatophyte species in domestic animals in Switzerland and examined the effectiveness of direct mycological examination (DME) for their detection compared to mycological cultures. In total, 3515 hair and skin samples, collected between 2008 and 2022 by practicing veterinarians, were subjected to direct fluorescence microscopy and fungal culture. Overall, 611 dermatophytes were isolated, of which 547 (89.5%) were from DME-positive samples. Cats and dogs were the main reservoirs of Trichophyton mentagrophytes and Microsporum canis, whereas Trichophyton benhamiae was predominantly found in guinea pigs. Cultures with M. canis significantly (p < 0.001) outnumbered those with T. mentagrophytes in DME-negative samples (19.3% versus 6.8%), possibly because M. canis can be asymptomatic in cats and dogs, unlike T. mentagrophytes, which is always infectious. Our data confirm DME as a reliable, quick, and easy method to identify the presence of dermatophytes in animals. A positive DME in an animal hair or skin sample should alert people in contact with the animal to the risk of contracting dermatophytosis.

PCR-terminal restriction fragment length polymorphism for direct detection and identification of dermatophytes in veterinary mycology

The biological diagnosis of dermatophytosis in veterinary medicine usually relies on direct microscopic examination and inoculation of the samples on appropriate culture media. However, identification of dermatophytes needs expertise, and cultures which require from days to weeks to be conclusive, may lack of sensitivity because of the quite common overgrowth of contaminants. Here we developed a polymerase chain reaction (PCR) assay based on terminal restriction fragment length polymorphism (TRFLP), which may improve sensitivity of the biological diagnosis and reduce the delay for initiation of treatment. This study was first conducted on pure cultures of various dermatophytes (27 species), yeasts (14 species) and moulds (45 species). After DNA extraction, the internal transcribed spacer (ITS)-28S region of ribosomal DNA was amplified with primers targeting specifically pathogenic dermatophytes, and species of interest were identified by TRFLP with appropriate restriction enzymes. After validation, this assay was applied to veterinary samples and results were compared to those obtained by direct microscopic examination and cultures. All target species were correctly identified, and none of the yeast or mould species was amplified, demonstrating specificity of the assay. Regarding clinical samples, the causative agent was detected by PCR-TRFLP from 97.1% of the samples with both positive direct microscopic examination and cultures. No dermatophytes were detected when both conventional tests were negative. PCR-TRFLP developed here demonstrated to be highly sensitive and specific, allowing rapid detection and direct identification of dermatophytes in veterinary practice. Therefore, this assay is especially suitable for the biological diagnosis of dermatophytosis in different animal species.

Proteolytic activity and cooperative hemolytic effect of dermatophytes with different species of bacteria

BACKGROUND AND PURPOSE

Globally, dermatophytes are the most common filamentous group of fungi causing cutaneous mycoses. Dermatophytes were shown to secrete a multitude of enzymes that play a role in their pathogenesis. There is limited data on co-hemolytic (CAMP-like) effect of different bacterial species on dermatophyte species. In this study, we sought to the evaluate exoenzyme activity and co-hemolytic effect of four bacteria on clinical dermatophytes isolated from patients in Shiraz, Iran.

MATERIALS AND METHODS

A total of 84 clinical dermatophyte species were isolated from patients suffering dermatophytosis and identified by conventional methods. Hemolytic activity was evaluated with Columbia 5% sheep blood agar. Proteolytic activity was determined by plate clearance assay method, using gelatin 8% agar. CAMP-like factor was evaluated with four bacteria, namely, S. areus, S.saprophyticus, S.pyogenes, and S.agalactiae. Fisher's exact test was run for statistical analysis.

RESULTS

T. mentagrophytes was the most predominant agent (27 [32.1%]) followed by T. verrucosum(20 [23.8%]), T. tonsurans (10 [11.9%]), Microsporum canis (7 [8.3%]), T. rubrum (6 [7.1%]), E. floccosum (6 [7.1%]), M. gypseum (5 [6%]), and T. violaceum (3[3.6%]). The most common clinical area of dermatophytosis was the skin. All the isolates expressed the zone of incomplete alpha hemolysis. All the isolates had CAMP- positive reaction with S. aureus and the other bacteria were CAMP-negative. All the isolates expressed proteolytic activity and no significant differences were noted among diverse genera of dermatophytes and severities of proteolytic activity.

CONCLUSION

This study indicated that hemolysin and proteolytic enzymes potentially play a role in dermatophyte pathogenesis and S. aureus could be considered as a main bacterium for creation of co-hemolytic effect in association with dermatophyte species.

Clinicomycological Study of Dermatophytosis in South India

Introduction:

Dermatophytic infections are commonly encountered a problem and constitute more than 50% of cases in dermatology outpatient departments. Diagnosis of these infections requires the proper use of laboratory methods.

Objectives:

This study was conducted to know the etiology of dermatophytosis in patients attending Tertiary Care Level Hospital in South India and to compare the efficacy of Sabouraud's dextrose agar (SDA) with actidione and dermatophyte test medium (DTM) in isolating and identifying dermatophytes.

Materials and Methods:

A total of 110 samples which included 101 skin samples and 9 hair samples from clinically suspected dermatophytosis were collected. Direct microscopy by KOH and culture on SDA with actidione and DTM were done.

Results:

Of 110 samples collected, 58.18% were KOH positive for fungal filaments and 56.36% were culture positive for dermatophytes. More number of cases were observed between age groups of 21–40 years. Males were more affected compared to females. Tinea corporis was the common clinical presentation observed (40%). Trichophyton rubrum (58.06%) was the predominant isolate recovered in all clinical presentations but Trichophyton violaceum was the most common isolate in tinea capitis. All culture positives were grown on both SDA with actidione and DTM. Appearance of growth was earlier on DTM that is, within 10 days compared to SDA with actidione where growth started appearing only after 10 days. This is statistically significant P < 0.0001 (χ² = 71.6). Species level identification on primary isolation was possible when grown on SDA with actidione and it was not possible with the growth on DTM on primary isolation.

Conclusion:

DTM is a good screening medium in laboratory diagnosis of dermatophytosis when compared to SDA with actidione. But DTM is inferior to SDA with actidione in identification of dermatophyte species.

Molecular epidemiology, phylogeny and evolution of dermatophytes

Dermatophytes are fungi that invade and propagate in the keratinized skin of mammals, including humans, often causing contagious infections. The species of medical concern belong to the genera Microsporum, Trichophyton, Epidermophyton (in their anamorphic state) and Arthroderma (in their telomorphic state), which were traditionally identified based on their morphology and biochemical characters. Nonetheless, limitations linked to the differentiation of closely related agents at species and strains level have been recently overcome by molecular studies. Indeed, an accurate identification of dermatophytes is pivotal for the establishment of effective control and prevention programs as well as for determining the most appropriate and effective antifungal therapies to be applied. This article reviews the DNA techniques and the molecular markers used to identify and to characterize dermatophyte species, as well as aspects of their phylogeny and evolution. The applications of typing molecular strain to both basic and applied research (e.g., taxonomy, ecology, typing of infection, antifungal susceptibility) have also been discussed.

Pathogenesis of dermatophytosis and tinea versicolor

Dermatophytoses are infections caused by keratinophilic fungi known as dermatophytes. Several steps are required for infection to take place: contact, adherence, and invasion of keratin layers. The severity of the infection depends on the type of agent, environmental factors, and the host immunologic status. Tinea versicolor is caused by the Malassezia spp yeasts, which are microorganisms that belong to normal biota in seborrheic areas, but some contributing factors, such as the application of oily preparations, creams, an increase in ambient humidity, corticosteroid abuse, or genetic predisposition can induce its overgrowth in both filamentous and yeast structures. Exposure to sunlight stimulates the production of azelaic acid, which causes the appearance of hypopigmented spots. Currently, there is no scientific explanation for hyperpigmented lesions.

The evolution of sex: a perspective from the fungal kingdom

Sex is shrouded in mystery. Not only does it preferentially occur in the dark for both fungi and many animals, but evolutionary biologists continue to debate its benefits given costs in light of its pervasive nature. Experimental studies of the benefits and costs of sexual reproduction with fungi as model systems have begun to provide evidence that the balance between sexual and asexual reproduction shifts in response to selective pressures. Given their unique evolutionary history as opisthokonts, along with metazoans, fungi serve as exceptional models for the evolution of sex and sex-determining regions of the genome (the mating type locus) and for transitions that commonly occur between outcrossing/self-sterile and inbreeding/self-fertile modes of reproduction. We review here the state of the understanding of sex and its evolution in the fungal kingdom and also areas where the field has contributed and will continue to contribute to illuminating general principles and paradigms of sexual reproduction.

Organization and evolutionary trajectory of the mating type (MAT) locus in dermatophyte and dimorphic fungal pathogens

Sexual reproduction in fungi is governed by a specialized genomic region, the mating type (MAT) locus, whose gene identity, organization, and complexity are diverse. We identified the MAT locus of five dermatophyte fungal pathogens (Microsporum gypseum, Microsporum canis, Trichophyton equinum, Trichophyton rubrum, and Trichophyton tonsurans) and a dimorphic fungus, Paracoccidioides brasiliensis, and performed phylogenetic analyses. The identified MAT locus idiomorphs of M. gypseum control cell type identity in mating assays, and recombinant progeny were produced. Virulence tests in Galleria mellonella larvae suggest the two mating types of M. gypseum may have equivalent virulence. Synteny analysis revealed common features of the MAT locus shared among these five dermatophytes: namely, a small size ( approximately 3 kb) and a novel gene arrangement. The SLA2, COX13, and APN2 genes, which flank the MAT locus in other Ascomycota are instead linked on one side of the dermatophyte MAT locus. In addition, the transcriptional orientations of the APN2 and COX13 genes are reversed compared to the dimorphic fungi Histoplasma capsulatum, Coccidioides immitis, and Coccidioides posadasii. A putative transposable element, pogo, was found to have inserted in the MAT1-2 idiomorph of one P. brasiliensis strain but not others. In conclusion, the evolution of the MAT locus of the dermatophytes and dimorphic fungi from the last common ancestor has been punctuated by both gene acquisition and expansion, and asymmetric gene loss. These studies further support a foundation to develop molecular and genetic tools for dermatophyte and dimorphic human fungal pathogens.

Scutular tinea of the scrotum: report of two cases

Infections caused by dermathophytes in the scrotal skin are uncommon especially due to Microsporum gypseum, which may form scutular or favus-like lesions. We report two patients with this type of tinea: one immune suppressed by HIV infection and another immunocompetent without comorbidity. In the literature we found only two reports in immunocompetent patients and some in immune suppressed with similar symptoms.

Subcutaneous infection by Microsporum gypseum

We report a case of subcutaneous infection caused by the dermatophyte Microsporum gypseum in an immunocompetent host. The patient acquired the infection in the knee through a traumatic inoculation of a splinter. To our knowledge this is the first case of subcutaneous infection caused by this fungus.

The dermatophytes

The etiologic agents of the dermatophytoses (ringworm) are classified in three anamorphic (asexual or imperfect) genera, Epidermophyton, Microsporum, and Trichophyton. Species capable of reproducing sexually belong in the teleomorphic genus, Arthroderma, of the Ascomycota. On the basis of primary habitat association, they may be grouped as geophilic (soil associated), zoophilic, and anthropophilic. Adaptation to growth on humans by most geophilic species resulted in diminished loss of sporulation, sexuality, and other soil-associated characteristics. The dermatophytes have the ability to invade keratinized tissue (skin, hair, and nails) but are usually restricted to the nonliving cornified layer of the epidermis because of their inability to penetrate viable tissue of an immunocompetent host. However, invasion does elicit a host response ranging from mild to severe. Acid proteinases, elastase, keratinases, and other proteinases reportedly act as virulence factors. The development of cell-mediated immunity correlated with delayed hypersensitivity and an inflammatory response is associated with clinical cure, whereas the lack of or a defective cell-mediated immunity predisposes the host to chronic or recurrent dermatophyte infection. Chronic dermatophytosis is mostly caused by Trichophyton rubrum, and there is some evidence that mannan produced by this fungus suppresses or diminishes the inflammatory response. Since dermatophytes cause a communicable disease, modes of transmission and control are discussed as well as a survey of recent trends in therapy. Collection of specimens, culture media, and tests for identification are also presented. Genetic studies have led to an understanding of incompatibility mechanisms, pleomorphism and variation, resistance to griseofulvin, and virulence. Molecular biology has contributed to our knowledge of the taxonomy and phylogenetic relationships of dermatophytes.

Dermatophytosis in northern Greece during the decade 1981-1990

Dermatophytic infections are very common in Greece. In the Mycological Laboratory of the Venereal and Skin Diseases Hospital in Thessaloniki, 6572 isolates of different dermatophytes were obtained from 17,120 patients examined. It is suggested that 5% of the people who present with skin problems in Greece suffer from dermatophyte infections. They are frequent causative agents of tinea pedis, tinea cruris, tinea corporis, tinea capitis and tinea unguium. In this paper, the species, the number and the prevalence of the dermatophytes were studied according to location and sex of the patients. The contribution of dermatophyte infections to the overall incidence of superficial fungal infection over 10 years was also studied.

Dermatophytes and dermatophytoses in the Milan area between 1970 and 1989

Between 1970 and 1989 we examined 13,019 patients with dermatophytoses in the Milan area, Northern Italy. The results obtained during the 1980-89 period were compared with those obtained in the years 1970-79. From the data collected, tinea corporis emerged as the most frequently observed dermatophytosis, followed by tinea pedis and unguium. As far as dermatophytes are concerned, the dermatological pattern is dominated by Microsporum canis and Trichophyton rubrum. Other species, such as Epidermophyton floccosum, T. mentagrophytes, M. gypseum, T. violaceum, T. verrucosum, T. tonsurans and T. schoenleinii, have progressively become less evident. Other mycetes, such as T. megninii, T. soudanense, M. langeroni, T. vanbreuseghemii, M. ferrugineum, sporadically isolated in the 1970-79 period, have disappeared in recent years. An analysis of the distribution and frequency of the dermatophytes according to the cutaneous area affected is reported.

Epidemiology of tinea pedis in marathon runners: prevalence of occult athlete's foot

Studies on the prevalence of tinea pedis, a frequently encountered dermatophytic infection, have been conducted mostly in swimmers although people who regularly practise other types of physical activities may also have a high rate of clinical or subclinical infection. This investigation was undertaken to establish the rate of infection in marathon runners, and to determine the incidence of occult athlete's foot disease in this population. Among samples obtained from 405 individuals, 22% were positive. The rate of infection was highest in the older age groups. The prevalence of infection was 24.2% in men and 6.1% in women. Trichophyton rubrum and Trichophyton mentagrophytes were the two species of dermatophytes most commonly isolated on culture. Occult athlete's foot disease represented 48% of cases with a positive culture. Finally, routine sampling of both feet was confirmed necessary to adequately establish the rate of infection: 26.9% of cases with a positive culture would have been missed by unilateral sampling. Other epidemiological factors were not clearly linked to the prevalence of disease in marathon runners: weight; presence of pet animals; practice of other sports; race and country of origin. In conclusion, we establish that marathon runners represent a population at risk for the occurrence of both clinical and subclinical tinea pedis infection.

Dermatophytosis due to Trichophyton rubrum in northern Greece during the decade 1981-1990

During the years 1981-1990 Trichophyton rubrum was the most frequent causative agent of dermatophytic infections in Northern Greece, especially in cases of tinea pedis, cruris, corporis, and unguium, as well as dermatophytosis of the hands. Between sexes there was a prevalence in women in tinea pedis and toenail infections. Men were particularly infected in the groin, the hands and the face. The chronic follicular dermatophytosis in the lower legs was also presented in women, but tinea corporis and fingernail infections showed no significant differences between the sexes. Also studied were the age of the patients, the inflammatory component of the lesions and the morphotypes of T. rubrum isolated.

Incidence of occult athlete's foot in swimmers

Athlete's foot is a dermatophytic infection frequently found in adults. This disease is, in some cases, asymptomatic. In order to evaluate the incidence of subclinical infection, we obtained 300 toe-web samples from the fourth interdigital space of 150 regular swimmers. More over, 66 specimens from the pool area were analysed. The method used was the carpet technique described by Mariat et al. (10). The fungal isolates were identified according to standard methods. A list of epidemiological data was completed for every swimmer. In our results, 22 swimmers had positive cultures (15%), 8 of these cases had no lesions (36%). They included 7 infections with Trichophyton mentagrophytes (87.5%) and one with T. rubrum (12.5%). We observed one case with a dual infection. Only one sample from the inanimate environment was positive. This study showed a significant incidence of occult athlete's foot in swimmers. To control this endemic problem, adequate preventive measures must be taken.

Tinea capitis. A clinicoetiologic correlation

A study of 50 patients with tinea capitis revealed that it affects school children of low socioeconomic status. Clinical diagnosis of grey patch, black dot, seborrheic, kerion, and pustular inflammatory varieties was made. In all, 37 cultures were positive for dermatophytes, wherein most were Trichophyton violaceum. Some grew T. rubrum, T. mentagropytes, and T. verrucosum. A correlation between the clinical variants and fungi was also attempted.

Antigenic relationship between downy and granular forms of Trichophyton mentagrophytes and Trichophyton rubrum

One strain each of granular and downy varieties of Trichophyton mentagrophytes and two strains each of granular and floccose colonial types Trichophyton rubrum were used for preparation of antigens. The antigens were analyzed by double diffusion against homologous and heterologous antisera raised in rabbits. A total of 17 distinct antigens were recognized, seven of which were common to two dermatophytes. Granular and downy varieties of the Trichophyton species produced on additional line of nonidentity. Cross reactions failed to establish any relationship between similar morphologic forms of different dermatophytes. One isolate of T. rubrum, which was originally the floccose culture type but changed into the granular form after artificial infection, showed an antigenic relationship to the floccose culture.

An epidemic of infection with Trichophyton tonsurans revealed in a 20-year survey of fungal infections in Chicago

Trichophyton tonsurans has long been recognized as an important, but hitherto uncommon, cause of tinea capitis in the United States. Today it is known to be more common, but infection of the glabrous skin by this organism is still not well appreciated. In an epidemiologic study during the two decades from 1961 to 1980, 1,292 isolates of thirteen species of dermatophytes were obtained from patients at Cook County Hospital, Chicago. During the last 3 years of study, T. tonsurans accounted for 207 cases (96%) of tinea capitis and ninety-seven cases (75%) of tinea corporis. Ninety-five percent of cases of tinea capitis caused by T. tonsurans occurred in children (59% girls, 41% boys). By contrast, 62% of cases of tinea corporis caused by that organism occurred in adults. Substantially more women than men were affected in a ratio of nearly six to one. The majority of the women were between 15 and 29 years of age; about half of all had lesions on the arm. Over the past 20 years, T. tonsurans has emerged as a major cause of both tinea capitis and tinea corporis in Chicago. The disproportionate number of cases of tinea corporis in women of childbearing age may be due to their more frequent contact with infected children.

The epidemiology of ringworm in racehorses caused by Trichophyton equinum var autotrophicum

The epidemiology of dermatomycocis due to Trichophyton equinum var autotrophicum was studied in a number of thoroughbred stables in south-east Queensland. The significant factors in the epidemiology were defined. The infection was readily transmitted, particularly by infected saddle-girths, on which the fungus could survive for 12 months. Mild abrasion from the saddle during work favoured the development of lesions and prolonged the recovery period. A pronounced age and seasonal incidence of the disease was demonstrated as young horses under the age of 3 years were most susceptible, and the majority of cases occurred in periods of high humidity.

Epidemiologic study of dermatophytoses in Salamanca (Spain)

An epidemiologic study of the dermatophytoses in Salamanca (Spain) from 1973 to 1976 was performed. Dermatophyte species were identified in 224 patients with clinical tinea infections; 31 bovines, 18 rodents and 70 soil samples. The prevalence of Trichophyton verrucosum and Epidermophyton floccosum was strikingly high in relation to other statistics. The most common clinical forms were tinea corporis and tinea cruris. Tinea capitis by anthropophilic species was uncommon.

Occlusion, carbon dioxide, and fungal skin infections

Occlusion of the skin renders it susceptible to acute fungal skin infections (dermatophytosis and candidiasis). Occlusion also raised carbon-dioxide (CO2) tensions at the skin's surface. Comparable CO2 tnesions have a pronounced effect on the morphology and metabolism of dermatophytes in vitro. It is postulated that dermatophyte conida and hyphae produce infective units under conditions of raised CO2 tensions, and that occlusion of the skin produces the concentrations of CO2 required for the conversion. Fungal skin infections might be prevented or controlled by interference with the action of CO2 or by prevention of its accumulation under wet, occlusive clothing.