title: Evaluation of Chitine synthase (CHS1) polymerase chain reaction assay in diagnosis of dermatophyte onychomycosis.
abstract: BACKGROUND
  Onychomycosis is one of the most prevalent dermatophytic diseases. Mycological methods used in the conventional diagnosis may not be optimal. PCR was reported as a reliable alternative in the diagnosis of dermatophytosis.
  
  
  METHODS
  A PCR method based on the amplification of the chitin synthase 1 gene was developed. The study included 119 strains of dermatophytes and non dermatophytic fungi, eight dermatophytic reference strains and 201 nail specimens from patients with dermatophytic onyxis. DNA extraction was carried out by using the QIAamp DNA extraction kit (Quiagen).
  
  
  RESULTS
  PCR positivity was based on the production of a specific 432 bp fragment. None of the investigated non dermatophytic strains was positive. Sensitivity of PCR was higher as compared to mycological examination (90.5% vs. 81.1%). PCR was positive in 31 onyxis cases with positive direct examination but negative or contaminated culture. In contrast, PCR was negative in 10 cases where both direct examination and culture were found positive.
  
  
  CONCLUSIONS
  PCR is an adequate tool for the diagnosis of dermatophytic onychomycosis. It is much adapted to cases where culture is negative or contaminated by overgrowing molds, which makes the identification of the causal agent problematic.
authors.affiliation: Laboratory of Parasitology-Mycology, Hospital Farhat Hached, Sousse, Tunisia. dhib.imen@yahoo.fr
authors.forename: I
authors.initials: I
authors.lastname: Dhib
authors.forename: A
authors.initials: A
authors.lastname: Fathallah
authors.forename: I B
authors.initials: IB
authors.lastname: Charfeddine
authors.forename: S G
authors.initials: SG
authors.lastname: Meksi
authors.forename: M B
authors.initials: MB
authors.lastname: Said
authors.forename: F
authors.initials: F
authors.lastname: Slama
authors.forename: R
authors.initials: R
authors.lastname: Zemni
mesh_terms: D003883:Arthrodermataceae / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification*; D002687:Chitin Synthase / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics* / Q000302:isolation & purification; D005656:Fungal Proteins / Q000235:genetics*; D005800:Genes, Fungal; D006801:Humans; D009172:Mycology / Q000379:methods*; D014009:Onychomycosis / Q000175:diagnosis* / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013045:Species Specificity; D014249:Trichophyton / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D002687:Chitin Synthase