Detection of Histoplasma capsulatum DNA in human samples by real-time polymerase chain reaction
Received 25 June 2009; accepted 9 October 2009.
Abstract
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.
aLaboratoire Hospitalo-Universitaire de Parasitologie-Mycologie Médicale, équipe EA3593, UFR de Médecine, Université des Antilles et de la Guyane, French Guiana
bLaboratoire de Biologie Médicale, Centre hospitalier de l'Ouest Guyanais Frank Joly, 97320 Saint Laurent du Maroni, Guyane française
Corresponding author. Service de Parasitologie-Mycologie Médicale (LHUPM), Centre Hospitalier Andrée Rosemon, BP 6006, rue des flamboyants, Cayenne, French Guiana. Tel.: +594-594-29-61-32; fax: +594-594-29-34-13.