Diagnosis of common dermatophyte infections by a novel multiplex real-time polymerase chain reaction detection/identification scheme.
BACKGROUND
In the absence of a functional dermatophyte-specific polymerase chain reaction (PCR), current diagnosis of dermatophytoses, which constitute the commonest communicable diseases worldwide, relies on microscopy and culture. This combination of techniques is time-consuming and notoriously low in sensitivity.


OBJECTIVE
Recent dermatophyte gene sequence records were used to design a real-time PCR assay for detection and identification of dermatophytes in clinical specimens in less than 24 h.


METHODS
Two assays based on amplification of ribosomal internal transcribed spacer regions and on the use of probes specific to relevant species and species-complexes were designed, optimised and clinically evaluated. One assay was for detecting the Trichophyton mentagrophytes species complex plus T. tonsurans and T. violaceum. The second assayed for the T. rubrum species complex, Microsporum canis and M. audouinii.


RESULTS
The analytical sensitivity of both assays was 0.1 pg DNA per reaction, corresponding to 2.5-3.3 genomes per sample. The protocol was clinically evaluated over 6 months by testing 92 skin, nail and hair specimens from 67 patients with suspected dermatophytosis. Real-time PCR detected and correctly identified the causal agent in specimens from which T. rubrum, T. interdigitale, M. audouinii or T. violaceum grew in culture, and also identified a dermatophyte species in an additional seven specimens that were negative in microscopy and culture.


CONCLUSIONS
This highly sensitive assay also proved to have high positive and negative predictive values (95.7% and 100%), facilitating the accurate, rapid diagnosis conducive to targeted rather than empirical therapy for dermatophytoses.
Second Dermatology Clinic, A. Syngros Hospital, Medical School, University of Athens, Ionos Dragoumi 4, Athens 11621, Greece. marabatz@med.uoa.gr
M
M
Arabatzis
L E S
LE
Bruijnesteijn van Coppenraet
E J
EJ
Kuijper
G S
GS
de Hoog
A P M
AP
Lavrijsen
K
K
Templeton
E M H
EM
van der Raaij-Helmer
A
A
Velegraki
Y
Y
Gräser
R C
RC
Summerbell
D003883:Arthrodermataceae / Q000145:classification / Q000302:isolation & purification*; D004271:DNA, Fungal / Q000032:analysis; D003881:Dermatomycoses / Q000175:diagnosis* / Q000382:microbiology; D006197:Hair / Q000382:microbiology; D006801:Humans; D016533:Mycological Typing Techniques; D009262:Nails / Q000382:microbiology; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D012867:Skin / Q000382:microbiology
D004271:DNA, Fungal