Present day concepts of the dermatophytes

Occurrence of Trichophyton verrucosum in cattle in the Ningxia Hui autonomous region, China

Background

Ningxia Hui Autonomous Region is an important cattle breeding area in China, and cattle breeding bases are located in this area. In Ningxia, dermatophytes have not been paid attention to, so dermatophytosis is becoming more and more serious. For effective control measures, it is important to determine the disease prevalence and isolate and identify the pathogenic microorganism.

Results

The study showed the prevalence of dermatophytes was 15.35% (74/482). The prevalence in calf was higher than adult cattle (p < 0.05). The morbidity was the highest in winter compared with autumn (p < 0.0001), summer (p < 0.05) and spring (p < 0.0001). The prevalence in Guyuan was the highest compared with Yinchuan (p < 0.05) and Shizuishan (p < 0.05). The incidence of lesions on the face, head, neck, trunk and whole body was 20.43, 38.71, 20.43, 10.75 and 9.68%, respectively. From all samples, the isolation rate of Trichophyton was highest (61.1%). The phylogenetic tree constructed showed that the 11 pathogenic fungi were on the same branch as Trichophyton verrucosum.

Conclusions

This study reports, for the first time, the presence of Trichophyton verrucosum in cattle in Ningxia and showed that the incidence of dermatophytosis is related to different regions, ages and seasons. A better knowledge of the prevalence of dermatophytosis of cattle may allow the adoption of more efficient control measures and prophylaxis.

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.

Role of Chrysosporium keratinophillum in the parasitic evolution of dermatophytes

Anti-dermatophytic activity of Chrysosporium keratinophillum against species of the genera Trichophyton, Microsporum and Epidermophyton floccosum was tested in vitro. When C. keratinophillum and different species of dermatophytes were inoculated on Sabouraud's dextrose agar plates 2 cm apart, no antagonistic effect of C. keratinophillum on the mycelial growth of dermatophytes was observed. However, conidia production was not observed on the hyphae of Trichophyton rubrum, Trichophyton tonsurans and E. floccosum grown near C. keratinophillum. The secretory substances released by C. keratinophillum inhibited the growth of T. rubrum, T. tonsurans, Trichophyton mentagrophytes var. interdigitale and E. floccosum at a concentration of 2,000 microg ml(-1) when tested by broth dilution technique. No inhibition of the growth was observed for Microsporum gypseum and Microsporum nanum. The anti-fungal activity of secretory substances released by C. keratinophillum was recorded to be heat stable. Results of the present study suggest that the anti-dermatophytic activity of the secretory substances of C. keratinophillum on T. rubrum, T. mentagrophytes var. interdigitale, T. tonsurans and E. floccosum may be responsible in part, for the absence of these dermatophyte species in soil. Considering the global prevalence of C. keratinophillum in soil one may speculate that the anti-dermatophytic activity of C. keratinophillum is one of the early events for the evolutionary divergence of saprophytic archi-dermatophytes to obligate parasitic dermatophyte species.

Seasonal 4-year investigation into the role of the alpine marmot (Marmota marmota) as a carrier of zoophilic dermatophytes1

Two hundred and six samples of alpine marmot (Mamota marmota) hair (148 from adults and 58 from young subjects), 102 soil samples from the entrances to the burrows of the above individuals and 20 control specimens (obtained from adjoining areas away from the burrow systems where the rodents are not usually present) were examined from May 1994 to September 1997. Seventy-five isolates belonging to six species of dermatophytes were found in 69 of the 206 hair samples examined (33.5%). Two species were zoophilic, Microsporum canis (7.8%) and Trichophyton mentagrophytes (11.2.%), and four geophilic, Microsporum cookei (2%), M. gypseum (5.8%), Trichophyton ajelloi (3.9%) and T. terrestre (5.8%). The prevalence of each species in the hair samples did not change significantly according to year, season (chi-squared test [limit significance: P <0.05] gives no significant values [P>0.05] both in year and in season comparison) or age/sex (adult versus juvenile: P=0.1; male versus female: P=0.8) of the marmot. Twenty-three of the 102 soil samples (22.5%) were positive for dermatophytes found in the hair of marmots from the same burrow systems. Five of the 20 control soil samples (25%) were positive for dermatophytes. One isolate of M. gypseum, three of T. terrestre and one of T. mentagrophytes were obtained. Compared with other free-ranging rodent hosts studied in Europe, this mycoflora is characterized by the presence and relatively high prevalence of M. canis, frequently reported in symptomatic and asymptomatic cats, dogs and fur animals. M. canis has not been isolated in other rodents in the wild. However, it has recently been reported in asymptomatic foxes (Vulpes vulpes) from northern Italy. The close link between V vulpes and M. marmota, with the former representing the most important mammal predator of the latter in the Alps (only a fraction of the predator's attacks result in the death of the rodent) may have favoured the adaptation of M. canis to this rodent host. The stable character of the M. canis/M. marmota relationship (no seasonally or annually related difference in the prevalence of this dermatophyte has been found) suggests the inclusion of the alpine marmot in the reservoir of this zoophilic pathogenic agent. In this situation, hibernation in labyrinthine burrow systems, where temperature and moisture ranges are quite uniform the whole year round, may favour the viability of M. canis arthroconidia, whose survival in mountain habitat might otherwise be compromised. This seems to be confirmed by the fact that the fungus has never been found in the control samples collected at a distance of 300 m from the outer edge of the sampled burrow systems.

Dermatophytes from cases of skin disease in cats and dogs in Turin, Italy

In urban environments, pet animals such as dogs and cats may be largely responsible for the progressive increase of zoophilic over anthropophilic dermatophytes in the aetiology of human dermatophytoses. Mapping, in each city, of the natural foci of zoophilic dermatophytes may thus be important for understanding the epidemiology of human dermatophytoses, and for planning preventive measures. We have surveyed dogs and cats suspected of carrying dermatophytic lesions in the Turin area. Hairs, skin scrapings and the contents of pustules or vesicles were inoculated on Dermasel agar supplemented with choramphenicol and cycloheximide. The mating type of the isolates was checked, testing their compatibility with the two mating types of Arthroderma simii Stockdale, Mackenzie and Austwick. We isolated dermatophytes from about 40% of the cases examined. Microsporum canis Bodin was the only dermatophyte found in the lesions. In the cats the lesions were more frequent, in the dogs more severe. Animals less than a year old and male dogs were most often affected. Some cases of transmission of the infection between animals and from animals to man are described. All the isolates of M. canis, tested for mating behaviour, were non-reactive.

Keratinophilic fungi isolated from soil of Italian parks in the province of Pavia

Soil samples collected from 9 parks in the Italian province of Pavia were baited with hair and feathers for the isolation of keratinophilic fungi. The dominant species were the teleomorphs Arthroderma gypsea, A. uncinatum, Ctenomyces serratus and Aphanoascus fulvescens with their anamorphs. Among the other species isolated, Amauroascus mutatus, Gymnascella dankaliensis, Gymnoascus intermedius and Gymnoascus reessii were recorded. The distribution of these fungi is discussed and related to previous records.

Some remarks concerning Trichophyton proliferans

We have had the opportunity to study an dermatophyte isolated from the face of a woman, as a result of a fall on the ground. We identified the strain as Trichophyton proliferans whose characteristics, together with a review of the works published about this dermatophyte, lead us to believe that we are dealing with an independent species and not a synonym of T. mentagrophytes var. erinacei.

Survey of human pathogenic actinomycetes and fungi in soil from Rome and other Italian areas

As part of a study sponsored by the Ministry of Health of Italy, a research program on pathogenic actinomycetes, keratinophilic and pathogenic fungi in soil was carried out. Two hundred soil samples, collected from different areas of the city of Rome, Calabria, Emilia Romagna, Latium, Apulia, Sardinia, Sicily, Tuscany and Umbria, were examined by several techniques to detect the widest possible variety of pathogenic actinomycetes and fungi. Seven isolates of Nocardia asteroides, four of Actinomadura madurae and one of Nocardiopsis dassonvillei were isolated for the first time from soil in Italy. In addition, numerous isolates of Petriellidium boydii, Aspergillus fumigatus, A. flavus, A. niger and keratinophilic fungi of the genera Microsporum, Trichophyton and Chrysosporium were also recovered.