Diagnostic PCR of dermatophytes – an overview

Abstract

The prevalence of onychomycosis is increasing steadily, sevenfold alone in the US within the last twenty years. An important aspect in this development is the demographic development of the human population of the industrial countries like Germany. A fast and accurate laboratory diagnosis is essential for successful treatment because 50% of the cases are misdiagnosed when relying on the clinical appearance only. The current diagnosis of dermatophytosis, based on direct microscopy and culture of the clinical specimen, is problematic given the lacking specificity of the former and the length of time needed for the latter. Molecular techniques can help to solve these problems. In recent years, a number of in-house PCR assays have been developed to identify dermatophytes directly from clinical specimens. Based on the "Mikrobiologisch-infektiologischen Qualitätsstandards (MIQ) für Nukleinsäure-Amplifikationstechniken" and the MIQE guideline (Minimum Information for Publication of Quantitative Real-Time PCR Experiments) 11 studies are reviewed which were published between 2007 and 2010. The present article evaluates the quality of the PCR assays regarding false positive and false negative results due to contamination, PCR format, statistical analysis, and diagnostic performance of the studies. It shows that we are only at the beginning of providing high quality PCR diagnosis of dermatophytes.

Diagnosis of dermatophytosis: an evaluation of direct examination using MycetColor® and MycetFluo®

“…An update on the currently available molecular techniques has recently been published by Jensen and Arendrup (2012) and Gräser et al (2012). However, despite the high sensitivity of these techniques, false-positive or falsenegative results were observed.…”

Clinico-Mycological Profile of Onychomycosis in a Tertiary Care Centre of Tripura

“…It has also been reported that 30-50% of microscopically identified onychomycosis cannot be cultivated and hence pathogen cannot be identified at the species level. [26] CONCLUSION Early diagnosis of onychomycosis is a challenge to the microbiologist. The sensitivity of microscopic detection technique using 20% KOH mount varies from 48-80%.…”

“…The sensitivity of microscopic detection technique using 20% KOH mount varies from 48-80%. [26] This leads to search of advanced techniques like various molecular diagnostic methods for rapid, stable and accurate alternative for identifying pathogenic fungi from the nail sample. Polymerase Chain Reaction (PCR) technique is presently undergoing evaluation and found that it can detect up to the species level within 48 hours.…”

A pilot study for the evaluation of pcr as a diagnostic tool in patients with suspected dermatophytoses

“…The PCR results in these samples could be affected by the inhomogeneous distribution of fungal DNA in the clinical material. In addition, as observed by Gräser et al,[12] the sensitivity of the PCR assays could be improved by the selective accumulation of fungal DNA during extraction with a simultaneous reduction of human DNA. In an absence of such a method for fungal DNA extraction, increasing the template volume could add to the fungal DNA available for amplification, and thus add to the sensitivity of the assay.…”

“…[12] Studies evaluating the diagnostic performance of PCR assays directly on clinical samples have been relatively rare. [13] Some of these studies have targeted the amplification of the Internal Transcribed Spacer ( its2 ) and 18S rDNA regions, chitin synthase 1 gene, and large subunit of rDNA.…”