The agony of choice in dermatophyte diagnostics-performance of different molecular tests and culture in the detection of Trichophyton rubrum and Trichophyton interdigitale

Dermatophytosis caused by dermatophytes of the genera Trichophyton and Microsporum belong to the most frequent mycoses worldwide. Molecular detection methods proved to be highly sensitive and enable rapid and accurate detection of dermatophyte species from clinical specimens. For the first time, we compare the performance of different molecular methods with each other and with conventional diagnostics in the detection of dermatophytoses caused by Trichophyton rubrum and Trichophyton interdigitale in clinical specimens (nail, skin and hair). The compared molecular methods comprise two already published PCR-ELISAs, a published quantitative RT-PCR as well as a newly developed PCR-ELISA targeting the internal transcribed spacer region. We investigated the sensitivity of the assays by analysing 375 clinical samples. In 148 specimens (39.5%) a positive result was gained in at least one of the four molecular tests or by culture, but the number of detected agents differed significantly between some of the assays. The most sensitive assay, a PCR-ELISA targeting a microsatellite region, detected 81 T. rubrum infections followed by an internal transcribed spacer PCR-ELISA (60), quantitative RT-PCR (52) and a topoisomerase II PCR-ELISA (51), whereas cultivation resulted in T. rubrum identification in 37 samples. The pros and cons of all four tests in routine diagnostics are discussed.