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Molecular Identification and Antifungal Susceptibility Patterns of Clinical Dermatophytes Following CLSI and EUCAST Guidelines.

ABSTRACT: Dermatophytes are associated with superficial infections in humans worldwide. The aim of the present study was to determine the species distribution and susceptibility patterns of clinical dermatophytes. Samples received for routine mycological processing from 124 suspected cases attending a dermatologic clinic in a tertiary care hospital were included in the study. On direct microscopy, 74.1% (92/124) were positive and 53.2% (66/124) grew on culture. The isolates were comprised of Trichophytoninterdigitale (56%) followed by Trichophytontonsurans (25.7%), Trichophytonrubrum (7.5%), Trichophytonviolaceum (4.5%), Microsporumgypseum (4.5%), and Trichophytonverrucosum (1.5%). Conventional mycological identification was concordant with ITS sequencing except for T.mentagrophytes. High minimum inhibitory concentration (MIC) values (geometric mean, >1 µg/mL) were observed for T.tonsurans and T.rubrum to terbinafine and griseofulvin. This study highlights the shift in epidemiology from T.rubrum to T.interdigitale. It also raises a concern of high MICs of terbinafine and griseofulvin among our isolates. Surveillance of antifungal susceptibility patterns can provide clinicians with local MIC data that can further aid in guiding better management in relapse cases of dermatomycosis.

SUBMITTER: Dabas Y

PROVIDER: S-EPMC5715923 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Molecular Identification and Antifungal Susceptibility Patterns of Clinical Dermatophytes Following CLSI and EUCAST Guidelines.

Dabas Yubhisha Y Xess Immaculata I Singh Gagandeep G Pandey Mragnayani M Meena Suneeta S

Journal of fungi (Basel, Switzerland) 20170323 2

Dermatophytes are associated with superficial infections in humans worldwide. The aim of the present study was to determine the species distribution and susceptibility patterns of clinical dermatophytes. Samples received for routine mycological processing from 124 suspected cases attending a dermatologic clinic in a tertiary care hospital were included in the study. On direct microscopy, 74.1% (92/124) were positive and 53.2% (66/124) grew on culture. The isolates were comprised of <i>Trichophyt ...[more]

PMID: 29371535

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Project description:BackgroundDermatophytes are a homogeneous group of species with low genetic diversity, and there are still many uncertainties about the boundaries among species.ObjectivesAiming at clarifying the relationships among species in the genus and introducing suitable genes for multilocus sequence typing (MLST), a new MLST scheme approach was developed to characterize the major pathogenic dermatophytes.MethodsWe performed maximum parsimony (MP), MrBayes, RAxML, and eBURST analyses, based on the MLST scheme to scrutinize the evolution within 95 clinical isolates and four reference strains belonging to the four major dermatophytes species. Then, the discriminatory power, pairwise genetic distances, ratio dN/dS, and sequence types (STs) of these isolates were determined. Also, to study taxonomy, sequences of the internal transcribed spacer (ITS), Beta-tubulin (BT2 ), and translation elongation factor 1-α (TEF-1α) genes of other dermatophytes species available in the GenBank were analyzed.ResultsFindings of the present study indicated that three genes: BT2, ITS, and TEF-1α, which showed the greatest diversity among dermatophyte species, were suitable for MLST. The most prevalent STs were seen among the species of Trichophyton interdigitale. Also, two new genotypes, i.e., XXVII and XXVIII, were introduced for T. interdigitale and Trichophyton mentagrophytes. The least informative sites were found in Epidermophyton floccosum, Trichophyton rubrum, and T. mentagrophytes, while the most informative sites were observed in T. interdigitale. Furthermore, the most informative locus was TEF-1α. The phylogenetic tree, constructed by the combination of the three genes, shows a new topological pattern that confirms the derivation of the anthropophilic and zoophilic genera from the geophilic genus. Also, the phylogenetic analyses and pairwise distances of the combination of the three loci showed that Trichophyton tonsurans and Trichophyton equinum were a species complex, where T. equinum is derived from T. tonsurans.ConclusionsResults of this study showed that MLST is very effective in determining the boundaries between species and taxonomy. Considering that there is no database for MLST dermatophytes, further studies are needed to determine the suitable genes for MLST. Also, the determination of STs in epidemiological studies and raising epidemiological information are helpful. This study was a new starting point to determine the ST and a foundation for a dermatophyte MLST database.

Project description:Aspergillus tamarii appears to be an emerging aetiological agent of human keratomycoses in South India. The investigated strains were isolated from six suspected fungal keratitis patients attending a tertiary care eye hospital in Coimbatore (Tamil Nadu, India), and were initially identified by the microscopic examinations of the scrapings and the cultures. Our data suggest that A. tamarii could be easily overlooked when identification is carried out based on morphological characteristics alone, while the sequence analysis of the calmodulin gene can be used successfully to recognize this species accurately. According to the collected clinical data, ocular trauma is a common risk factor for the infection that gradually developed from mild to severe ulcers and could be healed with an appropriate combined antifungal therapy. Antifungal susceptibility testing revealed that A. tamarii strains are susceptible to the most commonly used topical or systemic antifungal agents (i.e., econazole, itraconazole and ketoconazole) except for natamycin. Moreover, natamycin proved to be similarly less effective than the azoles against A. tamarii in our drug interaction tests, as the predominance of indifferent interactions was revealed between natamycin and econazole and between natamycin and itraconazole as well. Four and five isolates of A. tamarii were confirmed to produce cyclopiazonic acid (CPA) in RPMI-1640 - which is designed to mimic the composition of human extracellular fluids - and in yeast extract sucrose (YES) medium, respectively, which is a widely used culture medium for testing mycotoxin production. Although a ten times lower mycelial biomass was recorded in RPMI-1640 than in YES medium, the toxin contents of the samples were of the same order of magnitude in both types of media. There might be a relationship between the outcome of infections and the toxigenic properties of the infecting fungal strains. However, this remains to be investigated in the future.

Dataset Information

Molecular Identification and Antifungal Susceptibility Patterns of Clinical Dermatophytes Following CLSI and EUCAST Guidelines.

Publications

Molecular Identification and Antifungal Susceptibility Patterns of Clinical Dermatophytes Following CLSI and EUCAST Guidelines.

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