Detection of Histoplasma capsulatum DNA in human samples by real-time polymerase chain reaction.
The main aim of our study was to determine the added value of real-time polymerase chain reaction (PCR) for the diagnosis of Histoplasma capsulatum in routine biologic practice. No amplification signal was observed with the 18 non-H. capsulatum strains used to test the specificity of the protocol. The sensitivity threshold of the real-time PCR assay was about 10 fg of H. capsulatum DNA per microliter, tested with a 10-fold serial dilution of the positive control. We analyzed 348 human samples submitted for the routine diagnosis of systemic mycosis. Real-time PCR using the TaqMan system was evaluated against direct microscopic examination and culture. Among the 341 samples without PCR inhibition (n = 7), 66 tested positive by culture, whereas 74 tested positive by real-time PCR. Sensitivity of the real-time PCR assay was estimated at 95.4% and specificity at 96.0% with respect to culture, widely considered to be the gold standard method; however, the molecular approach in fact produced better sensitivity and specificity results. Moreover, for the 38 samples that tested negative by direct examination but positive by culture, the culture method took a mean of 31 days longer than the PCR method to generate results. The protocol presented here may be very useful for improving routine histoplasmosis diagnosis.
Laboratoire Hospitalo-Universitaire de Parasitologie-Mycologie Médicale, équipe EA3593, UFR de Médecine, Université des Antilles et de la Guyane, French Guiana.
Stephane
S
Simon
Vincent
V
Veron
Rachida
R
Boukhari
Denis
D
Blanchet
Christine
C
Aznar
D000328:Adult; D004271:DNA, Fungal / Q000032:analysis* / Q000235:genetics; D005260:Female; D006658:Histoplasma / Q000235:genetics*; D006660:Histoplasmosis / Q000175:diagnosis / Q000382:microbiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
D004271:DNA, Fungal