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Journal of Clinical Microbiology, Jul 1997, 1691-1695, Vol 35, No. 7
A Mathis, R Weber, H Kuster and R Speich
Early diagnosis of Pneumocystis carinii pneumonia, a life-threatening
complication in immunosuppressed patients, may lower morbidity and
mortality. We have developed a one-tube nested PCR assay for the detection
of P. carinii in respiratory specimens. Four primers were selected from the
sequence of the small-subunit rRNA gene of P. carinii to amplify a 265-bp
fragment, and their specificities for P. carinii were confirmed by both
theoretical evaluations (by computer-assisted comparison with the sequences
in GenBank) and empirical evaluations (with DNA from medically important
fungi and diagnostic samples). The assay was optimized for routine
diagnostic use. Processing of the clinical samples is rapid and simple
(digestion with proteinase K directly in PCR buffer at room temperature in
the presence of 10% Chelex 100 and no further purification steps). Bovine
serum albumin (1 mg/ml) and glycerol (10%) in the amplification buffer
reduced the number of samples inhibitory to the PCR, as assessed by control
reactions containing a size-modified target. A total of 749 clinical
specimens (312 bronchoalveolar lavage, 403 sputum or induced sputum, and 34
other specimens) from 507 patients (295 human immunodeficiency virus
[HIV]-infected and 164 non-HIV-infected patients and 48 patients whose HIV
status was unknown) were tested by PCR, and the results were compared with
those of an indirect immunofluorescence assay (IFA). Concordant results
were obtained for 732 samples (646 negative and 86 positive). There were 17
discrepant results: 12 were PCR positive and IFA negative, and 5 were PCR
negative and IFA positive. After resolution of the discrepant results by
review of the patients' clinical data, the sensitivity and specificity were
94.8 and 99.1%, respectively, for PCR and 93.8 and 100%, respectively, for
IFA. In conclusion, the short procedure time and the technical ease of this
PCR assay render it suitable for implementation in routine diagnostic
laboratories.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Simplified sample processing combined with a sensitive one-tube nested PCR assay for detection of Pneumocystis carinii in respiratory specimens
Institute of Parasitology, University of Zurich, Switzerland.
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