Molecular Characterisation and Phylogenetic Analysis of Dermatophytic Fungi Isolated from Tinea Capitis in Northwest Nigeria Using Sequence of the 28S rRNA

The detection and identification of fungal DNA from clinical samples is one of the fundamental approaches in biomedicine. The incidence, distribution, and control of dermatophytes has progress significantly and the use of phylogenetic species concepts based on rRNA regions have enhanced the taxonomy of dermatophyte species; however, the use of 28S rDNA genes has certain limitations. This gene has been used in dermatophyte taxonomy with limited enumeration; we appraised the sequence disparity within and among groups of the species, the gene ranking in identification, phylogenetic analysis, and taxonomy of 32 strains of eight dermatophyte species. In this study, a set of primers was adopted to amplify the target followed by a partial sequencing of the rDNA. The utilization of a pairwise nucleotide differentiation, an affinity was observed among eight dermatophyte species, with disparity among species ranging from 0 to 197 base pair (bp). Intra-species bp differences were found within strains of Trichophyton eriotrephon, Trichophyton bullosum, Trichophyton simii (Trichophyton genus), Microsporum audouinii, and Trichophyton tonsurans (Microsporum and Trichophyton genus, respectively); however, only some strains of Trichophyton eriotrephon were found to be invariant having three genotypes. Trichophyton tonsurans exhibited most intra-species variability. The characterization and construction of a phylogenetic tree of 28S rDNA gene on dermatophyte species provide a bedrock of an additional finding of connections between species. However, 28S rRNA capture provides a novel method of effective and sensitive detection of dermatophytes lodged in human skin scale. We report for the first time the emergence of T. eriotrephon, T. bullosum, T. simii, T. benhamiae, and Ctenomyces serratus dermatophytes from Tinea capitis in Nigeria.

Epidemiology of infections due to zoophilic dermatophyte trichophyton simii, an update

Trichophyton simii is an important zoophilic dermatophyte. It has two different names, one for the asexual form (the anamorph state) that occurs in the vertebrate host, and the other for the sexual form (teleomorph also called “perfect state”) produced by mating between anamorphs. The sexual state of T. simii belongs to the genus Arthroderma in the family Arthrodermataceae of the phylum Ascomycota of the Kingdom fungi. Zoophilic Trichophyton species include Trichophyton equinum, T. bullosum, members of the T. mentagrophytes complex, T. simii, and T. verrucosum. The clinical lesions caused by T. simii in humans and animals are usually inflammatory and erythematous. It can be distinguished from other Trichophyton species by its faster growth on agar media, forming finely granular colonies with white-to-pale yellow color on reverse and distinctive to fusiform 3–7 septate macroconidia converting into chlamydospores in older cultures, and pyriform microconidia, and inability to perforate hair in-vitro, and produce the enzyme urease . Trichophyton simii is known to infect monkeys, chickens, dogs, and humans worldwide, though infections are sporadic and epidemic potential and zoonotic risk for humans is low; this dermatophyte is also known to occur as a geophilic species in several countries. The literature search generated a lot of data on T. simii infections from several countries, namely India, Sri Lanka, Japan, Iraq, Iran, Saudi Arabia, Belgium, France, the USA, and Brazil; many of the reports lacked details of clinical lesions and did not mention about treatment/outcome of infections. The results are analyzed and presented concisely in the tables. There is need for investigating the epidemiology of T. simii infections in countries from where, human T. simii infections have been reported, and occurrence of this dermatophyte in soil by employing conventional mycological methods and a newly developed PCR technique based on ITS genomic sequences of this dermatophyte.

Mycotic infections in animals in India: An update

This review traces the early records of mycotic infections in India, and presents an update of animal mycoses reported from several parts of India. The types of mycoses covered are the dermatophytosis (ringworm) in domestic animals due to well-known species of zoophilic dermatophytes, viz. Trichophyton simii, T. mentagrophytes, T. verrucosum, Microsporum canis and M. nanum, and the geophilic dermatophyte, M. gypseum, Aspergillus spp, Cryptococcus species and other yeast like fungi, histoplasma and blastomyces. The brief clinical and demographic features of infections in different animals are described. A particularly noteworthy finding in literature search is the report of clinical infections in one dog and two cows by an anthropophilic dermatophyte, T. rubrum from Belgachia, Kolkata, West Bengal in 1954. Veterinary scientists are urged to investigate the possible occurrence of infections in animals due to other pathogenic fungi including the dimorphic ones like Histoplasma and Blastomyces.