Epizootic and epidemic dermatophytose outbreaks caused byTrichophyton mentagrophytesfrom rabbits in Portugal, 2015

Sheep serve as a reservoir of Trichophyton mentagrophytes genotype V infection

Human infections by Trichophyton mentagrophytes occur mainly due to contact with diseased animals. In Iran, T. mentagrophytes genotype V is the most prevalent variant of the fungus. We aimed to determine the animal reservoir of T. mentagrophytes genotype V infection. The study was done on a total of 577 dermatophyte strains obtained from animals with signs of dermatophytosis and human patients. The list of extensively sampled animals included sheep, cows, cats and dogs. For human cases, epidemiological data were collected. All dermatophyte isolates from animals along with 70 human isolates morphologically similar to T. verrucosum and T. mentagrophytes genotype V were identified by rDNA internal transcribed spacer region restriction fragment length polymorphism analysis and DNA sequencing. A total of 334 animal dermatophyte strains were identified as Microsporum canis, T. mentagrophytes genotype V, T. verrucosum, Nannizzia gypsea, T. mentagrophytes genotype II*, T. mentagrophytes genotype VII, T. quinckeanum, and N. fulva. All clinical isolates identified as T. mentagrophytes genotype V originated from skin and scalp infections. Almost all veterinary isolates of T. mentagrophytes genotype V were cultured from sheep, but epidemiological data on animal-to-human transmission of T. mentagrophytes genotype V infection were limited and we found evidence in favor of interhuman transmission. In Iran, sheep maintain T. mentagrophytes genotype V population and therefore serve as animal reservoir of respective infections. The role of sheep as the source of human dermatophytosis due to T. mentagrophytes genotype V isolates is yet to be proven.

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.

DNA topoisomerase 2 gene polymorphism in dermatophytes

BACKGROUND

Dermatophytes are a group of keratinophilic fungi of medical importance. Despite a relatively long history of molecular taxonomic studies, there is still a need for information on genetic polymorphism in wider variety of genomic loci.

OBJECTIVES

Our goal was to study partial DNA topoisomerase 2 gene (TOP2) polymorphism in dermatophytes.

METHODS

We performed DNA sequencing of TOP2 in 26 dermatophyte species along with ribosomal internal transcribed spacer (ITS) sequencing.

RESULTS

The number of polymorphic sites in TOP2 data set was similar to that one in ITS data set. Nannizzia species formed paraphyletic group in TOP2 tree. Trichophyton simii was paraphyletic in concatenated TOP2-ITS tree, one of its two clades contained solely Iranian isolates.

CONCLUSIONS

Our results revealed several unresolved problems in the taxonomy of dermatophytes, including probable polyphyly of the genus Nannizzia and the species T simii.

Atypical Dermatophytosis in 12 North American Porcupines (Erethizon dorsatum) from the Northeastern United States 2010-2017

Twelve wild North American porcupines (Erethizon dorsatum) out of a total of 44 of this species examined in an 8-year period were diagnosed with dermatopathies while being cared for at two wildlife rehabilitation clinics. Biopsy and necropsy were performed on seven and five animals, respectively. Atypical dermatophytosis was diagnosed in all cases. Lesions consisted of diffuse severe epidermal hyperkeratosis and mild hyperplasia with mild lymphoplasmacytic dermatitis and no folliculitis. Dermatophytes were noted histologically as hyphae and spores in hair shafts, and follicular and epidermal keratin. Trichophyton sp. was grown in 5/6 animals where culture was performed, with a molecular diagnosis of Arthroderma benhamiae/Trichophyton mentagrophytes in these five cases. Metagenomic analysis of formalin-fixed paraffin-embedded tissue samples from three cases identified fungi from 17 orders in phyla Basidiomycota and Ascomycota. Alteration of therapy from ketaconazole, which was unsuccessful in four out of five early cases, to terbinafine or nitraconazole led to the resolution of disease and recovery to release in four subsequent animals. In all, six animals were euthanized or died due to dermatopathy, no cases resolved spontaneously, and six cases were resolved with therapy. The work we present demonstrates an atypical lesion and anatomical distribution due to dermatophytosis in a series of free-ranging wild porcupines and the successful development of novel techniques for extracting and sequencing nucleic acids from fungus in archival formalin-fixed paraffin-embedded animal tissue.

A microtiter plate-based quantitative method to monitor the growth rate of dermatophytes and test antifungal activity

Dermatophytosis is one of the most common superficial fungal infections, which is mainly caused by filamentous fungi such as Trichophyton species. A challenging aspect in dermatophyte research is the lack of a straightforward method to measure the rate of growth, in particular when growing dermatophytes in small volumes such as in microtitre plates. However, one characteristic of dermatophytes is their ability to produce compounds such as ammonia that make the growth medium more alkaline. The objective of this study was to test whether the change in pH in a liquid medium, colourimetrically established using the indicator phenol red, was linearly and directly proportional to the growth rate for Trichophyton rubrum and Trichophyton interdigitale. The changes in the colour determined by the phenol-red based assay showed a good correlation with the amount of fungal biomass over an incubation period of 24-120 h. The functionality of the phenol red assay was also validated in experiments on the growth of T. rubrum in the presence of antifungals. The changes in colour showed a clear dose-response relationship compounds and enabled determination of the minimum inhibitory concentration. The phenol red assay is thus a simple and straightforward assay to monitor the rate of growth of Trichophyton spp. and test antifungal activity.

Species boundaries in the Trichophyton mentagrophytes / T. interdigitale species complex

The fungi Trichophyton mentagrophytes and T. interdigitale are closely related species, causing superficial infections in humans and other mammals. The status of these taxa is a field of long-lasting debates. To clarify their phylogenetic relationships within the genus Trichophyton and sharpen the species boundaries, we performed sequencing of four T. mentagrophytes genomes and also evaluated three previously published multilocus data sets. We performed computational species delimitation analysis on all available in GenBank internal transcribed spacer region (ITS) sequences of Trichophyton spp. Phylogenomic data, phylogenetic network, and species delimitation analyses implied that T. mentagrophytes and T. interdigitale belong to the same phylogenetic species. However, we argue that taxonomic status quo should be retained, from the perspective of epidemiological data and the principle of taxonomic stability. Since there is a correlation between ITS genotype and epidemiological source of an isolate, restriction of T. interdigitale to purely anthropophilic ITS genotypes seems to be reasonable.

Phagocytic activity and oxygen metabolism of peripheral blood granulocytes from rabbits experimentally infected with Trichophyton mentagrophytes

Introduction

Phagocytic activity and oxygen metabolism of peripheral blood granulocytes from rabbits with experimental trichophytosis were assessed by flow cytometry.

Material and Methods

Virulent species of T. mentagrophytes var. granulosum (Tm-K) isolated from rabbits with natural trichophytosis was used for experimental infection. The phagocytic activity of granulocytes was measured in whole blood by flow cytometry using the commercial Phagotest kit. Oxidative burst was measured in whole blood by flow cytometry using the commercial Bursttest kit.

Results

It was found that rabbits were susceptible to infection with Trichophyton mentagrophytes under experimental conditions. The analysis of the phagocytic activity indices and oxygen metabolism of granulocytes in peripheral blood of infected rabbits showed that changes of the indices were connected with the progression and regression of the disease. A significant decrease in phagocytic activity and oxygen metabolism was observed during development of fungal lesions and it remained similar throughout the progress of the disease. The highest means of the percentage of activated and ingesting phagocytes and a significant increase in the mean fluorescence intensity (representing the number of ingested bacteria) were observed during spontaneous recovery. Therefore, the decrease or increase in the indices of phagocytic activity and oxygen metabolism of granulocytes from rabbits experimentally infected with T. mentagrophytes is somehow related to the progress of infection and suppressive activity of the fungus, whose elimination during recovery caused significant increases in investigated indices of non-specific cellular immunity.

Conclusion

The results of the present investigation confirm that the mechanism of oxygen-dependent killing is crucial in infections caused by T. mentagrophytes.

Phagocytic Activity and Oxygen Metabolism of Peripheral Blood Granulocytes from Rabbits Experimentally Infected with Trichophyton Mentagrophytes

Introduction

Phagocytic activity and oxygen metabolism of peripheral blood granulocytes from rabbits with experimental trichophytosis were assessed by flow cytometry.

Material and Methods

Virulent species of T. mentagrophytes var. granulosum (Tm-K) isolated from rabbits with natural trichophytosis was used for experimental infection. The phagocytic activity of granulocytes was measured in whole blood by flow cytometry using the commercial Phagotest kit. Oxidative burst was measured in whole blood by flow cytometry using the commercial Bursttest kit.

Results

It was found that rabbits were susceptible to infection with Trichophyton mentagrophytes under experimental conditions. The analysis of the phagocytic activity indices and oxygen metabolism of granulocytes in peripheral blood of infected rabbits showed that changes of the indices were connected with the progression and regression of the disease. A significant decrease in phagocytic activity and oxygen metabolism was observed during development of fungal lesions and it remained similar throughout the progress of the disease. The highest means of the percentage of activated and ingesting phagocytes and a significant increase in the mean fluorescence intensity (representing the number of ingested bacteria) were observed during spontaneous recovery. Therefore, the decrease or increase in the indices of phagocytic activity and oxygen metabolism of granulocytes from rabbits experimentally infected with T. mentagrophytes is somehow related to the progress of infection and suppressive activity of the fungus, whose elimination during recovery caused significant increases in investigated indices of non-specific cellular immunity.

Conclusion

The results of the present investigation confirm that the mechanism of oxygen-dependent killing is crucial in infections caused by T. mentagrophytes.