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Onychomycosis is one of the most prevalent dermatophytic diseases. Mycological methods used in the conventional diagnosis may not be optimal. Multiplex (MX) PCR was reported as a reliable alternative. Dermatophyte gene sequence records were used to design a MX PCR for detection and identification of dermatophytes in nail specimens. A MX PCR method based on the amplification of the chitin synthase 1 and internal transcribed spacer genes was developed. The study included 93 strains of dermatophytes and non-dermatophytic fungi, six dermatophytic reference strains and 201 nail specimens from patients with dermatophytic onyxis. DNA extraction directly from nail samples was carried out by using the QIAamp DNA extraction kit (Quiagen). A set of primers was designed and their specificity was assessed. MX PCR detected the causal agent in specimens from which Trichophyton rubrum and T. interdigitale grew in culture and also identified a dermatophyte species in an additional 32 specimens that were negative in microscopy and culture. None of the investigated non-dermatophytic strains was positive. Sensitivity of MX PCR was higher as compared to mycological examination (97% vs. 81.1%). MX PCR for direct detection of dermatophytes from nail samples yielded mixed flora in 32.8% of samples. MX PCR proved sensitive and adequate for the diagnosis of dermatophytic onychomycosis. It is much adapted to cases where culture is negative or contaminated by overgrowing moulds, which makes the identification of the causal agent problematic., (© 2013 Blackwell Verlag GmbH.)

Onychomycosis is the most frequently encountered nail disease and may be difficult to diagnose and treat. The objective of this study was to determine the prevalence, the clinical and mycological characteristics of onychomycosis in central Tunisia. It is a retrospective study performed over a 22-year period (1986-2007). It included 7151 patients (4709 women and 2442 men) with suspected fingernails and/or toenails onychomycosis. The patients were referred to the Mycology-Parasitology Laboratory of Farhat Hached hospital in Sousse for mycological examination. Both direct microscopy and culture of the nail material were performed to diagnose and identify the causative fungal species. Onychomycosis was confirmed in 78.6% of investigated patients (5624/7151). The positivity rate was higher in women as compared with men. In both men and women, fingernails were most frequently involved than toenails. No significant relation was found between gender and toenails onychomycosis, whereas fingernails were frequently involved in women. As far as aetiological agents are considered, dermatophytes, yeast and moulds were responsible for 49.9%, 47.4% and 2.7% of onyxis cases respectively. In fingernail infections, yeast were the most frequent fungi (83.6%), Candida albicans being the leading species (51.6%). In contrast, in toenail infections, dermatophytes were more frequent (74.1%). Trichophyton rubrum was by far the dominant species (88.1%). Yeast were observed more frequently in women whereas dermatophytes were more common in men. Moulds were involved in 4.2% of cases. The most frequent species were Aspergillus sp. and Chrysosporium sp. Onychomycosis is a frequent disease in central Tunisia. T. rubrum is the predominant agent in toenails infection and yeast, mainly C. albicans, in fingernails onychomycosis., (© 2012 Blackwell Verlag GmbH.)