Polymorphisms in the ITS rDNA regions for differentiating strains of theTrichophyton mentagrophytescomplex in Sfax-Tunisia

Comparison of in vitro activities of newer triazoles and classic antifungal agents against dermatophyte species isolated from Iranian University Hospitals: a multi-central study

BACKGROUND

Dermatophytes have the ability to invade the keratin layer of humans and cause infections. The aims of this study were the accurate identification of dermatophytes by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism method and sequencing and comparison between the in vitro activities of newer and established antifungal agents against them.

METHODS

Clinical specimens of patients from five Iranian university laboratories were entered in this study. Samples were cultured on sabouraud dextrose agar medium. For molecular identification, extracted DNAs were amplified by the universal fungal primers ITS1 and ITS4, and digested with MvaI enzymes. The antifungal susceptibility test for each isolate to terbinafine, griseofulvin, caspofungin, fluconazole, itraconazole, luliconazole, and isavuconazole was performed, according to the microdilution CLSI M38-A2 and CLSI M61 standard methods.

RESULTS

Two hundred and seven fungi species similar to dermatophytes were isolated of which 198 (95.6%) were dermatophytes by molecular assay. The most commonly isolated were Trichophyton mentagrophytes (76/198), followed by Trichophyton interdigitale (57/198), Trichophyton rubrum (34/198), Trichophyton tonsurans (12/198), Microsporum canis (10/198), Trichophyton simii (3/198), Epidermophyton floccosum (3/198), Trichophyton violaceum (2/198), and Trichophyton benhamiae (1/198). The GM MIC and MIC₉₀ values for all the isolates were as follows: terbinafine (0.091 and 1 μg/ml), griseofulvin (1.01 and 4 μg/ml), caspofungin (0.06 and 4 μg/ml), fluconazole (16.52 and 32 μg/ml), itraconazole (0.861 and 8 μg/ml), isavuconazole (0.074 and 2 μg/ml), and luliconazole (0.018 and 0.25 μg/ml).

CONCLUSION

Trichophyton mentagrophytes, Trichophyton interdigitale, and Trichophyton rubrum were the most common fungal species isolated from the patients. luliconazole, terbinafine, and isavuconazole in vitro were revealed to be the most effective antifungal agents against all dermatophyte isolates.

[Morphological and molecular differentiation by high resolution melting curves (HRMA) and sequencing of the Trichophyton mentagrophytes complex in human strains in Valparaíso, Chile]

Trichophyton mentagrophytes complex is the most frequent agent found in dermatophyte isolates after Trichophyton rubrum. It is divided into 3main groups: (1) Trichophyton benhamiae and related species; (2) Trichophyton simii and 2related species, Trichophyton quinckeanum and Trichophyton schoenleinii; and (3) T. mentagrophytes, T. interdigitale, and related species. They are all difficult to identify by morphophysiology. With the aim of classifying them at the species level, a descriptive study was performed on 17 isolated clinical strains identified in the Mycology Laboratory of the Universidad de Valparaíso as belonging to the T. mentagrophytes complex. They were compared with 3 reference strains (T. mentagrophytes CBS 318.56, T. interdigitale CBS 428.63, Trichophyton erinacei CBS 511.73). Morphophysiological and molecular tests were performed by high resolution melting analysis curves and ITS regions sequencing. Phenotypically, 3 species of the complex were identified. Molecular analyses reclassified all the species as belonging to T. interdigitale. In conclusion, no reliable morphophysiological patterns were established to differentiate between the species of the complex. Molecularly, all the strains studied were classified as T. interdigitale.

Reconstruction of phylogenetic relationships in dermatomycete genus Trichophyton Malmsten 1848 based on ribosomal internal transcribed spacer region, partial 28S rRNA and beta-tubulin genes sequences

Trichophyton spp. are important causative agents of superficial mycoses. The phylogeny of the genus and accurate strain identification, based on the ribosomal ITS region sequencing, are still under development. The present work is aimed at (i) inferring the genus phylogeny from partial ITS, LSU and BT2 sequences (ii) description of ribosomal ITS region polymorphism in 15 strains of Trichophyton interdigitale. We performed DNA sequence-based species identification and phylogenetic analysis on 48 strains belonging to the genus Trichophyton. Phylogenetic relationships were inferred by maximum likelihood and Bayesian methods on concatenated ITS, LSU and BT2 sequences. Ribosomal ITS region polymorphisms were assessed directly on the alignment. By phylogenetic reconstruction, we reveal major anthropophilic and zoophilic species clusters in the genus Trichophyton. We describe several sequences of the ITS region of T. interdigitale, which do not fit in the traditional polymorphism scheme and propose emendations in this scheme for discrimination between ITS sequence types in T. interdigitale. The new polymorphism scheme will allow inclusion of a wider spectrum of isolates while retaining its explanatory power. This scheme was also found to be partially congruent with NTS typing technique.