Molecular and Phenotypic Characterization of Nannizzia (Arthrodermataceae)

Phylogenetic studies of the family Arthrodermataceae have revealed seven monophyletic dermatophyte clades representing the genera Trichophyton, Epidermophyton, Nannizzia, Lophophyton, Paraphyton, Microsporum, and Arthroderma. Members of the genus Nannizzia are geo- or zoophiles that occasionally infect humans. With the newly proposed taxonomy, the genus Nannizzia comprises thirteen species, i.e., Nannizzia aenigmatica, N. corniculata, N. duboisii, N. fulva, N. graeserae, N. gypsea, N. nana, N. incurvata, N. perplicata, N. persicolor, N. praecox, and two novel species. Nannizzia polymorpha sp. nov. was isolated from a skin lesion of a patient from French Guiana. For the strain originally described as Microsporum racemosum by Borelli in 1965, we proposed Nannizzia lorica nom. nov. The species are fully characterized with five sequenced loci (ITS, LSU, TUB2, RP 60S L1 and TEF3), combined with morphology of the asexual form and physiological features. A key to the species based on phenotypic and physiological characters is provided.

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.

Detection and identification of dermatophyte fungi in clinical samples using a commercial multiplex tandem PCR assay

We evaluated the performance of a commercial multiplex tandem polymerase chain reaction (PCR) for detection of dermatophytes and other fungi in skin and nail specimens by (1) testing a range of fungal and bacterial reference cultures, (2) retrospectively testing a set of skin and nail specimens with known microscopy and culture results, and (3) prospectively testing skin and nail specimens in parallel to microscopy and culture. The AusDiagnostics Dermatophytes and Other Fungi assay accurately detected and identified a range of common dermatophytes to species, species complex or genus level, as well as Candida, Aspergillus and Scopulariopsis spp. It was unable to detect uncommon dermatophytes such as Nannizzia fulva (previously Microsporum fulvum), and Paraphyton cookei (previously Microsporum cookei). PCR identified a dermatophyte in 25.9% of prospective specimens which were culture negative. Sensitivity, specificity, positive predictive value, and negative predictive value were highest where microscopy and PCR results were combined, versus microscopy and culture combined, which highlights the significant contribution of microscopy in the diagnostic pathway. This assay has the potential to reduce the workload and results turnaround time associated with culturing and identification of dermatophytes, although microscopy remains important.

Species distribution of the main aetiologic agents causing skin dermatophytosis in Colombian patients: A 23-year experience at a Mycological Reference Center

BACKGROUND

Dermatophytosis is one of the most frequent superficial mycoses in the world.

MAIN AIM

To describe the cases of skin dermatophytosis and its main aetiologic agents in patients referred to a Mycological Reference Laboratory in Medellín, Colombia.

METHODS

A retrospective study was carried out with records of patients referred between 1994 and 2016 to the Corporación para Investigaciones Biológicas (CIB), Medellín-Colombia, because of clinical suspicion of skin dermatophytosis.

RESULTS

Of a total of 5628 clinical records of patients with suspicion of skin dermatophytosis analysed, 2780 (49.4%) had a proven or probable dermatophytosis diagnosis, 2774 cultures were performed, and aetiologic agents were isolated in 2576 samples (92.9%). The most frequently isolated aetiologic agents were Trichophyton rubrum (44.3%), followed by Trichophyton mentagrophytes complex (33.3%), Epidermophyton floccosum (12.4%), Nannizzia gypseum complex (5.7%, formerly Microsporum gypseum), Microsporum canis (3.5%) and Trichophyton tonsurans (0.8%). The most frequent clinical forms were tinea pedis (72.7%) and tinea corporis (12.7%). In addition, a group of patients (0.9%) developed mixed infections by two dermatophyte agents and another (4.1%) developed infections in more than one anatomical site.

CONCLUSIONS

The results of the present study are coherent with previous reports where T rubrum and T mentagrophytes complex were the main causative agents of dermatophytosis. However, the increased incidence of N gypsea complex over M canis is worth highlighting.