Diagnosis of dermatophyte nail infections with a quick specific detection of Trichophyton rubrum

Abstract

The aim of this study is to assess the usefulness of the Polymerase Chain Reaction (PCR) as an alternative technique to the classic method of diagnosis of dermatophytes.

To that end, a fast extraction method has been used, in two steps, and also a multiplex PCR in order to detect dermatophytes and, more in particular, Trichophyton rubrum from DNA extracted out of sick nails and previous tests.

As DNA controls we have used human DNA and DNA from a series of dermatophytes and non– dermatophytic fungi.

A prospective descriptive study was carried out of cases and controls from our population in Lugo, where a total of 28 nail samples were analyzed separately, both by two PCR and a multiplex format.

The comparison between the traditional method of diagnosis in nails (microscopy and culture) and the PCR using DNA directly extracted from the nails shows an excellent concordance between the microscopy and the PCR.

In addition, with the study by PCR the number of samples identified with dermatophytes increased from a 20 percent to more than a 40 percent mainly due to the identification of T.rubrum by PCR in positive samples by microscopy but negative in culture.

In conclusion, this rapid diagnostic test represents a significant increase in sensitivity in the characterization of the onychomycosis.