Arthroderma-benhamiae-Stämme aus Deutschland: Morphologische und physiologische Merkmale der anamorphen Formen

Changes in fungal taxonomy: mycological rationale and clinical implications

Numerous fungal species of medical importance have been recently subjected to and will likely continue to undergo nomenclatural changes as a result of the application of molecular approaches to fungal classification together with abandonment of dual nomenclature. Here, we summarize those changes affecting key groups of fungi of medical importance, explaining the mycological (taxonomic) rationale that underpinned the changes and the clinical relevance/importance (where such exists) of the key nomenclatural revisions. Potential mechanisms to mitigate unnecessary taxonomic instability are suggested, together with approaches to raise awareness of important changes to minimize potential clinical confusion.

[Zoophilic dermatophytes during coronavirus pandemic in Germany]

During the coronavirus pandemic, significantly more pets were probably bought and kept. This study focuses on whether more zoophilic dermatophytes have subsequently been isolated and which species predominate. In the 1‑year period from March 2020 through February 2021, all zoophilic dermatophytes from all submissions to the Mölbis laboratory were recorded. Both the cultural and the molecular evidence of fungal detection from skin scrapings, hair roots, and, in single cases, from nails, were considered. For dermatophyte DNA (Deoxyribonucleic acid) detection, an in-house polymerase chain reaction (PCR) - enzyme-linked immunosorbent assay (ELISA) was used. In distinct cases, identification of dermatophytes was confirmed by sequencing of the internal transcribed spacer (ITS) region of the rDNA, and of the gene of the translation elongation factor (TEF)-1α. In 579 (2.56%) of 22,575 samples studied in the year 2020/2021, zoophilic dermatophytes were detectable with PCR-ELISA and/or by cultivation. In comparison, the proportion of zoophilic dermatophytes was 2.03% in the 1‑year period 2014/2015, and only 1.6% in 2018/2019. The 579 zoophilic dermatophytes were identified as follows: Trichophyton (T.) benhamiae 186 (32.1%), T. mentagrophytes 173 (29.9%), T. quinckeanum 110 (19.0%), Microsporum (M.) canis 78 (13.5%), T. verrucosum 22 (3.8%), Nannizzia (N.) persicolor 8 (1.4%), T. erinacei 1 (0.2%), and T. equinum 1 (0.2%). T. benhamiae had the highest prevalence from June to September 2020, then again in December. T. quinckeanum is associated with a sharp increase in the mice population in Germany in 2020; a significant increase was found in the months September 2020 to January 2021. T. mentagrophytes had a conspicuous peak in September. Compered with that M. canis in November. Up to 50% of the dermatophytoses caused by T. mentagrophytes, T. quinckeanum, and M. canis affected children and adolescents, while in the case of T. benhamiae it was as much as two thirds. Tinea corporis was the most common, followed by tinea faciei and tinea capitis. M. canis infections affected the capillitium more frequently than the face. Zoophilic dermatophytes were increasingly isolated during the coronavirus pandemic in Germany when compared to previous year periods. In first place, the dermatophyte T. benhamiae from guinea pigs was found in children and adolescents. A significant proportion of dermatophytoses concerned adults. T. quinckeanum is an emerging pathogen in Germany with unprecedented high infection rates in 2020.

Immunomodulatory responses of differentially polarized macrophages to fungal infections

Macrophages, the first line of defense against invasive fungi in the innate immune system, are widely distributed in the blood and tissues of the body. In response to various internal and external stimulators, macrophages can polarize into classically activated macrophages (M1) and alternatively activated macrophages (M2). These two types of polarized macrophages play different roles in antifungal activity and in maintaining the steady-state balance between inflammation and tissue repair. However, the antifungal mechanisms of M1- and M2-type macrophages have not been fully described. In this review, the immune regulatory mechanisms against pathogenic fungi of these two classical types of macrophages in various tissues are summarized. The effects of antifungal factors on macrophage differentiation are also highlighted. The description of these data, on the one hand provides valuable insight for future investigations and also highlights new strategies for the treatment of pathogenic fungal infections.

Mating analyses of Trichophyton benhamiae offspring reveals linkage of genetic markers used in taxonomy

Mating experiments were conducted with four clinical Trichophyton benhamiae isolates, genetically similar to the Trichophyton benhamiae CBS 112371, featuring the plus mating type and with two minus type strains. One minus type strain belonged to the white subgroup, and the other minus type strain, DSM 6916, showed genetic kinship to the yellow subgroup. Only two plus type strains were able to form mature, pigmented gymnothecia with DSM 6916. These two plus type strains demonstrated dark pigmentation and powdery mycelium on Takashio agar, whereas the other three strains exhibited a low degree of pigmentation on the same medium. All five plus strains were able to mate with the minus type strain of their own white subgroup. Cultures from single ascospore isolates showed highly variable morphology and pigmentation. Three genetic markers (ITS, mating type, EF1 alpha) were analyzed in polymerase chain reaction (PCR) experiments with optimized primers and PCR conditions to discriminate between subgroups. Furthermore, RAPD-PCR was used to generate a DSM 6916-specific DNA-fragment which served as an additional genetic marker. Assessing the isolates with recombinant genotypes, it was found that three genetic markers behave like linked genes. The recombination of plus mating type went together with ITS, EF1 alpha and RAPD marker of the DSM 6916 parental strain and was most frequently isolated, whereas plus types recombinants in this case were completely missing. This shows a high imbalance in mating type distribution of recombinants.

[Dermatophytosis caused by rare anthropophilic and zoophilic agents]

The basis for effective treatment of any dermatomycosis is the correct and timely identification of the pathogen, which allows the targeted choice of the most suitable antimycotic and is important for the prevention of repeated infections. In recent years, infections with dermatophytes seem to have increased. In fact, from 2007 to 2018, there was an increase in the number of samples processed in the Mycology Laboratory of the Department of Dermatology at the University Hospital Jena. The most common isolated dermatophytes between 2007 and 2018 were Trichophyton (T.) rubrum, T. interdigitale, Microsporum (M.) canis and T. benhamiae. However, dermatophytoses may also be caused by rare anthropophilic agents such as Epidermophyton floccosum, zoophiles such as T. verrucosum, T. quinckeanum or Nannizzia (N.) persicolor as well as by geophiles such as N. gypsea. Therefore, these dermatophytes should at least be known, so that in case of unusual observations investigations can be performed accordingly. Changes in the pathogen spectrum of dermatophytoses have taken place over time and it is expected that the occurrence of dermatophytes will be subject of continuous fluctuations, which may mean that the incidence of some of these "rare" dermatophytes, as described here in five clinical examples, may be changing.

Genes Encoding Proteolytic Enzymes Fungalysin and Subtilisin in Dermatophytes of Human and Animal Origin: A Comparative Study

Dermatophytes are among the most successful fungal pathogens in humans, but their virulence mechanisms have not yet been fully characterized. Dermatophytic fungi secrete proteases in vivo, which are responsible for fungal colonization and degradation of the keratinized tissue during infection. In the present study, we used PCR to investigate the presence of genes encoding fungalysins (MEP) and subtilisins (SUB) in three dermatophyte species whose incidence is increasing in Europe: the anthropophilic Trichophyton rubrum (n = 58), zoophilic Microsporum canis (n = 33), and Trichophyton benhamiae (n = 6). MEP2 and SUB4 genes were significantly correlated with T. rubrum; MEP3 and SUB1 were mostly frequently harbored by M. canis; and MEP1, 2, and 4 and SUB3-7 were most frequently harbored by T. benhamiae isolates (p < 0.05). Furthermore, MEP1-5 and SUB1-3 genes were significantly more prevalent among human clinical isolates of M. canis (n = 17) than among asymptomatic cat isolates of M. canis (n = 16; p < 0.05). Unidentified MEP and/or SUB genes in some isolates in the current study may suggest that other gene repertoires may be involved in the degradation of keratin. The presented analysis of the incidence of MEP and SUB virulence genes in three dermatophyte species of diverse origins provides an insight into the host-fungus interaction and dermatophyte pathogenesis.

[Dynamic diversity of dermatophytes]

BACKGROUND

Many dermatologists do not understand the perpetual adjustments in the dermatophyte nomenclature.

OBJECTIVES

The aim is to explain the background and the development of methods that have led to previous and current changes of dermatophyte taxonomy and to the detection of new dermatophytes.

METHODS

In this article we evaluate the recent literature on this topic and our own results in the fields of dermatophyte identification, their detection, and of the associated taxonomic developments.

RESULTS

Today, the phylogenetic species concept is the basis of taxonomic classification, including that of dermatophytes. Genetic techniques have decisively advanced this and are state of the art nowadays. The detection of new dermatophyte species was often triggered by clinical observations and by morphologically conspicuous cultures that prompted their subsequent exact mycological characterization. Even today not all species of dermatophytes are unequivocally defined.

CONCLUSIONS

By exclusively using selected genetic characteristics for the construction of phylogenetic trees additional taxonomically relevant features are neglected. Therefore it is necessary to better integrate data derived from morphologic, physiologic, ecologic and pathophysiologic observations into phylogenetic analyses. Dermatologists are still asked to contribute such information.

Trichophyton benhamiae and T. mentagrophytes target guinea pigs in a mixed small animal stock

Trichophyton benhamiae is an emerging zoonotic dermatophyte. We present a case of a small animal stock infected with two Trichophyton species. T. benhamiae was isolated from 15 out of 26 (58%) guinea pigs including two morphologically different phenotypes. Eight guinea pigs were infected with T. benhamiae and T. mentagrophytes simultaneously. The animals showed alopecia and crusts or no clinical signs at all. T. benhamiae was not detected in rats, rabbits and mice kept in the same stock.