Introduction of a dermatophyte polymerase chain reaction assay to the diagnostic mycology service in Scotland.

BACKGROUND

Dermatophytes are the major cause of superficial mycoses in samples submitted to Clinical Mycology, Glasgow. The most prevalent species is Trichophyton rubrum as identified classically by microscopy and culture. Recent advances in polymerase chain reaction (PCR) technology were examined for the feasibility of introducing a T. rubrum real-time PCR assay into a routine diagnostic service.

OBJECTIVE

To improve the diagnostic mycology service by the introduction of a real-time PCR test for T. rubrum.

METHODS

The DNA from 4972 nail and skin samples was obtained using the Qiagen QIAsymphony automated extractor. This DNA was subjected to real-time PCR using T. rubrum-specific primers and a probe.

RESULTS

During phase 1 of the study, 862 samples were analysed; 446 of 470 specimens that grew T. rubrum were detected by PCR. Out of 4110 samples analysed during phase 2, 753 T. rubrum infections were diagnosed and reported within 72 h. A total of 3357 samples were negative for a fungal infection by PCR and microscopy; these were also reported within 72 h.

CONCLUSIONS

A vast reduction in the turnaround times can be achieved using this technique as opposed to classical methods. Samples which are PCR negative but microscopy positive are still subjected to culture. Screening samples for their suitability for PCR prior to processing eliminates the application of PCR for T. rubrum on inappropriate samples such those from the scalp or pityriasis versicolor.