Molecular Strain Typing of Clinical Isolates, Trichophyton rubrum using Non Transcribed Spacer (NTS) Region as a Molecular Marker.

INTRODUCTION: Dermatophytes are a group of fungi which infect keratinized tissues and causes superficial mycoses in humans and animals. The group comprises of three major genera, Trichophyton, Microsporum and Epidermophyton. Among them Trichophyton rubrum is a predominant anthropophilic fungi which causes chronic infections. Although, the infection is superficial and treatable, reinfection/coinfection causes inflation in the treatment cost. Identifying the source and mode of transmission is essential to prevent its transmission. Accurate discrimination is required to understand the clinical (relapse or reinfection) and epidemiological implications of the genetic heterogeneity of this species. Polymorphism in the Non Transcribed Spacer (NTS) region of ribosomal DNA (rDNA) clusters renders an effective way to discriminate strains among T. rubrum. AIM: To carry out the strain typing of the clinical isolates, Trichophyton rubrum using NTS as a molecular marker. MATERIALS AND METHODS: Seventy T.rubrum clinical isolates obtained from April-2011-March 2013, from Sri Ramachandra Medical Centre, Chennai, Tamil Nadu, India, were identified by conventional phenotypic methods and included in this prospective study. The isolates were then subjected to Polymerase Chain Reaction (PCR) targeting two subrepeat elements (SREs), TRS-1 and TRS-2 of the NTS region. RESULTS: Strain-specific polymorphism was observed in both subrepeat loci. Total, nine different strains were obtained on combining both TRS-1 and TRS-2, SREs. CONCLUSION: The outcome has given a strong representation for using NTS region amplification in discriminating the T. rubrum clinical isolates. The method can be adapted as a tool for conducting epidemiology and population based study in T. rubrum infections. This will help in future exploration of the epidemiology of T. rubrum.

Molecular strain typing of Trichophyton mentagrophytes (T. mentagrophytes var. interdigitale) using non-transcribed spacer region as a molecular marker.

Background & objectives: : Dermatophytes are keratinophilic fungi that infect keratinized tissues of human and animal origin. Trichophyton mentagrophytes is considered to be a species complex composed of several strains, which include both anthropophiles and zoophiles. Accurate discrimination is critical for comprehensive understanding of the clinical and epidemiological implications of the genetic heterogeneity of this complex. Molecular strain typing renders an effective way to discriminate each strain. The objective of the study was to characterize T. mentagrophytes clinical isolates to sub-species level using molecular techniques and non-transcribed spacer (NTS) region as marker. Methods: Sixty four T. mentagrophytes clinical isolates were identified by phenotypic methods. These were subjected to polymerase chain reaction targeting three sub-repeat elements (SREs), TmiS0, TmiS1 and TmiS2 of the NTS region. Sequence analysis of internal transcribed spacer (ITS) region of different types was also done. Results: Strain-specific polymorphism was observed in all three loci. Totally, 13 different PCR types were obtained on combining all the three SREs loci. No variation was observed in the ITS region. Interpretation & conclusions: The study described the usefulness of molecular strain typing technique for the discrimination of the T. mentagrophytes isolates. This will help for the future explorations into the epidemiology of T. mentagrophytes and its complex.