Titel: Detection and identification of pathogenic dermatophytes using multiplex real-time PCR assays
Art: Abstractautor
Session: Workshop 05
Diagnostic Stewardship - "Meet the needs of your partners!" (FG DKM, FG QD)

Referent: Franziska Wittig (Rötha OT Mölbis)

Abstract - Text

Introduction: Fungal infections of nails, skin and hair caused by dermatophytes such as Trichophyton (T.) spp., Microsporum (M.) spp. or Epidermophyton (E.) spp. are one of the most common human infections in the world. As the epidemiology varies between different dermatophyte species a specific diagnosis plays an important role to ensure a targeted therapy. In order to evaluate the DermaGenius multiplex real-time PCR assays (PathoNostics), real-time PCR results were compared to routine diagnostic methods including culture detection, microscopy and a standard PCR-ELISA assay.

Methods: After isolating DNA of 31 clinically isolated skin specimens and 18 cultures, dermatophytes were identified macroscopically, microscopically and molecularbiologically as well as analysed using the DermaGenius assay. Sanger sequencing of both, the internal transcribed spacer (ITS) region of the ribosomal DNA and the translation elongation factor alpha (TEF1α) gene was used when routine diagnostics could not give a definite result.

Results: In total, all (n = 49) clinical specimens and cultures could be detected with the DermaGenius assay. Out of 49 samples, the DermaGenius assay could identify 76% correctly by their specific melting temperature. Fourteen samples were detected but not differentiated including T. soudanense (n = 1) identified as T. rubrum, T. erinacei (n = 2) as T. benhamiae, T. equinum (n = 1) as T. tonsurans and M. ferrugineum (n = 1) as M. canis. Although different variants of T. mentagrophytes (n = 4), T. quinckeanum (n = 2) and T. schoenleinii (n = 1) species were detected by real-time PCR, they all showed similar melting temperatures to either T. interdigitale or T. mentagrophytes.

Conclusions: The DermaGenius multiplex real-time PCR assays (PathoNostics) are able to identify the most frequently isolated clinically prevalent dermatophytes and are suitable for routine molecular diagnostic laboratories as they enable high samples throughput with limited hands-on time. However, the identification and differentiation of less common dermatophytes as well as variants of T. mentagrophytes is still complicated since they are phylogenetically very closely related. After taking the anamnesis of patients or a fungal culture into consideration, only sequencing enables an identification of dermatophytes that could not be detected during routine diagnostics.