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Journal of Clinical Microbiology, 07 1996, 1769-1772, Vol 34, No. 7
AB Balatbat, GW Jordan, YJ Tang and J Silva Jr
Cryptosporidium parvum is a coccidian protozoan that causes diarrhea in
humans, often chronic and severe in patients with AIDS. Conventionally,
diagnosis is made by concentration of stools followed by acid-fast staining
(AF) or immunofluorescent staining. The threshold of detection in human
stool specimens by these methods may require the presence of 50,000
(immunofluorescent staining) to 500,000 (AF) oocysts per g of stool. In
this study, a nested PCR assay was developed to detect C. parvum DNA
directly from stool specimens. After extraction of DNA from formalinized
stool, a 400-bp fragment of C. parvum DNA was amplified with two 26-mer
outer primers. The amplicon from this reaction was amplified with a second
primer pair. With these nested primers, a 194- bp DNA fragment was
amplified and confirmed as C. parvum DNA by internal probing with an
enzyme-linked chemiluminescence system. This PCR-based test allowed the
detection of 500 oocysts per g of stool or 100 ng of C. parvum DNA. Studies
indicate that the primers utilized are specific for the DNA of C. parvum.
DNA sequences were also detected in stool specimens from 4 of 28 patients
previously reported negative by AF. In summary, a rapid, sensitive, and
specific assay for the detection of C. parvum directly from stool specimens
has been developed. This test has the potential for detecting asymptomatic
infection, monitoring the response to therapy, and detecting the organism
in environmental sources.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Detection of Cryptosporidium parvum DNA in human feces by nested PCR
Division of Infectious Diseases, University of California, Davis Medical Center, Sacramento 95817, USA.
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