Molecular strain typing of Trichophyton rubrum indicates multiple strain involvement in onychomycosis

Background Trichophyton rubrum is an important cause of onychomycosis. Molecular strain typing methods have recently been developed to address questions of epidemiology and source of relapse following treatment. Objectives To determine whether T. rubrum nail infections are caused by one or more strains of this fungus. Methods Nail specimens from 10 patients with onychomycosis due to T. rubrum were cultured and five colonies per culture plate were selected for molecular strain typing. DNA was extracted from these isolates and subjected to a polymerase chain reaction-based typing method that analyses variations in numbers of repetitive elements in the non-transcribed spacer region of the ribosomal RNA gene repeats. Results In six of 10 specimens, there were two or more T. rubrum strain types present. Conclusions This preliminary study suggests that in many cases of fungal nail infection by T. rubrum, multiple strains are involved. This has important implications for epidemiological studies and possibly for therapy.