Evaluation of DermaGenius, a multiplex real-time PCR to identify dermatophytes directly from specimens

Christina Kuenzli1, Cornelia Ottiger2, Hans Fankhauser2, Michael Oberle*2

Author address: 

1 Medics Labor AG, Bern, Switzerland, 2 Kantonsspital Aarau, Aarau, Switzerland

Abstract: 

Background: Traditional analysis of dermatophytes is long-lasting and needs experienced technicians. Molecular analysis would be faster and more specific. Here, we assess if a multiplex rtPCR assay could replace traditional dermatophyte analysis.

Materials/methods: Specimens were stained with Calcofluor Withe and microscopically examined (200 x magnifications) and cultured on Sabouraud and Dermatophyte agar plates at room temperature/ 4 weeks. The multiplex rtPCR kit DermaGenius® (Pathonostics, NL) was applied for the molecular detection of Candida albicans, Trichophyton rubrumT. interdigitaleT. tonsuransT. mentagrophytesT. soudaneseT. violaceumMicrosporum canisM. audouiniiEpidermophyton floccosum, T. benhamiae and T. verrucosum. Extracted fungal DNA from the specimens, according to the manufacturer’s protocol, was amplified on Rotor Gene Q. Dermatophyte species were differentiated by melting curve analysis.

Results: Retrospective evaluation of 309 traditionally analysed specimens showed growth of true dermatophyte species (26%), possible contaminants such as moulds (6%), microscope positive / culture negative (9%) and microscope / culture negative (59%) specimens. In a prospective evaluation 70 specimens were analysed by traditional means and by multiplex rtPCR in parallel. No discrepancy was seen in 48 negative and 15 positive specimens. Four specimens were positive only by rtPCR (3x T. rubrum and 1x C. albicans) and three culture positive probes were negative by rtPCR (2x Aspergillus sp. and 1x Fusarium sp. both not included in the DermaGenius® kit).

Conclusions: The multiplex rtPCR Derma Genius assay covers 96% of our cultured dermatophyte species, missing Microsporum fulvum and Trichosporon inkin. Therefore, rare or atypical dermatophytes have still to be analysed by culture. DermaGenius® rtPCR is fast, and is robust to contamination, but the interpretation of the melting curve analysis can be demanding. If a broad-spectrum fungal rtPCR would allow replacing the culture and how rtPCR can cost-effectively be implemented into the routine laboratory shall be discussed.

2019

Poster: 

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abstract No: 

P2199

Full conference title: 

European Congress of Clinical Microbiology & Infectious Diseases 2019
    • ECCMID 29th (2019)