Rapid detection of Candida albicans in clinical blood samples by using a TaqMan-based PCR assay.
We describe a rapid and reproducible PCR assay for quantitation of the Candida albicans ribosomal DNA (rDNA) in clinical blood samples based on the TaqMan principle (Applied Biosystems), in which a signal is generated by cleavage of a template-specific probe during amplification. We used two fluorogenic probes based on universal, fungus-specific primers, one for the detection of C. albicans species DNA and one for the detection of all Candida genus DNA. C. albicans blastoconidia mixed with whole blood in a titration experiment yielded a linear PCR signal over a range of 3 orders of magnitude. The TaqMan-based PCR assay for C. albicans exhibited a low limit of detection (5 CFU/ml of blood) and an excellent reproducibility (96 to 99%). While the C. albicans species-specific probe had 100% specificity for C. albicans, all Candida genus-specific probes cross-reacted with other organisms likely to coinfect patients with C. albicans infections. On the basis of these data, we determined the C. albicans loads with a species-specific probe from 122 blood samples from 61 hematology or oncology patients with clinically proven or suspected systemic Candida infections. Eleven positive samples exhibited a wide range of C. albicans loads, extending from 5 to 100,475 CFU/ml of blood. The sensitivity and specificity of the present assay were 100 and 97%, respectively, compared with the results of blood culture. These data indicate that the TaqMan-based PCR assay for quantitation of C. albicans with a species-specific probe provides an attractive alternative for the identification and quantitation of C. albicans rDNA in pure cultures and blood samples.
Maaroufi
Younes
Y
Department of Microbiology and Infectious Diseases, Institut Jules Bordet, 1000 Brussels, Belgium.
Heymans
Corine
C
De Bruyne
Jean-Marc
JM
Duchateau
Valerie
V
Rodriguez-Villalobos
Hector
H
Aoun
Michel
M
Crokaert
Françoise
F
D001769:Blood / Q000382:microbiology*; D002176:Candida albicans / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D002177:Candidiasis / Q000175:diagnosis / Q000382:microbiology*; D004271:DNA, Fungal / Q000032:analysis; D004275:DNA, Ribosomal / Q000032:analysis; D016469:Fungemia / Q000175:diagnosis / Q000382:microbiology; D006801:Humans; D016533:Mycological Typing Techniques; D016133:Polymerase Chain Reaction / Q000379:methods*; D015203:Reproducibility of Results; D013045:Species Specificity; D019914:Taq Polymerase / Q000378:metabolism*; D013997:Time Factors
D004271:DNA, Fungal; D004275:DNA, Ribosomal; D019914:Taq Polymerase