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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060
EISSN: 1678-8060
Vol. 93, No. 5, 1998, pp. 639-646
Bioline Code: oc98122
Full paper language: English
Document type: Research Article
Document available free of charge

Memórias do Instituto Oswaldo Cruz, Vol. 93, No. 5, 1998, pp. 639-646

 en Evaluation of DNA Recombinant Methodologies for the Diagnosis of Plasmodium falciparum and their Comparison with the Microscopy Assay
L Urdaneta; P Guevara & JL Ramirez

Abstract

Since 1984, DNA tests based on the highly repeated
subtelomeric sequences of Plasmodium falciparum (rep 20)
have been frequently used in malaria diagnosis. Rep 20 is very
specific for this parasite, and is made of 21 bp units, organized
in repeated blocks with direct and inverted orientation. Based in
this particular organization, we selected a unique consensus
oligonucleotide (pf-21) to drive a PCR reaction coupled to
hybridization to non-radioactive labeled probes. The pf-21 unique
oligo PCR (pf-21-I) assay produced DNA amplification fingerprints
when was applied on purified P. falciparum DNA samples
(Brazil and Colombia), as well as in patient's blood samples from
a large area of Venezuela. The performance of the Pf-21-I assay
was compared against Giemsa stained thick blood smears from
samples collected at a malaria endemic area of the Bolívar
State, Venezuela, at the field station of Malariología in
Tumeremo. Coupled to non-radioactive hybridization the pf-21-I
performed better than the traditional microscopic method with a
r=1.7:1. In the case of mixed infections the r value of P.
falciparum detection increased to 2.5:1. The increased
diagnostic sensitivity of the test produced with this homologous
oligonucleotide could provide an alternative to the
epidemiological diagnosis of P. falciparum being currently
used in Venezuela endemic areas, where low parasitemia levels and
asymptomatic malaria are frequent. In addition, the DNA
fingerprint could be tested in molecular population studies.

Keywords
Plasmodium falciparum - diagnosis - polymerase chain reaction - malaria

 
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