ABSTRACT
An evaluation of 3 different methods for malaria diagnosis was carried out in an urban area of low endemicity on the Pacific coast of Colombia. Samples were collected from 833 symptomatic patients at a malaria clinic and examined by the polymerase chain reaction (PCR), quantitative buffy coat (QBC; Becton Dickinson, Franklin Lakes, NJ) method, and the traditional thick blood smear. The prevalence of Plasmodium falciparum malaria was 5.88% by thick blood smear, 7.34% by the QBC method, and 21.87% by PCR. The agreement between microscopists was 99.5%. The agreement between the QBC method and thick blood smear was 96.13% (n = 745). Samples positive by PCR but negative by thick blood smear or conversely negative by PCR and positive by thick blood smear were usually of low-level parasitemias. All 3 methods showed agreement in 76.3% of the samples. Sixty-nine (18.8%) samples were positive by PCR but negative by the other 2 methods. Ten samples were positive by both the QBC method and thick blood smear but negative by PCR; most of them had low-level parasitemias. The use of malaria diagnostic methods for epidemiologic surveillance is discussed.
Subject(s)
Malaria, Falciparum/diagnosis , Plasmodium falciparum/isolation & purification , Animals , Antimalarials/therapeutic use , Blood/parasitology , Blotting, Southern , Chloroquine/therapeutic use , Colombia/epidemiology , Cross-Sectional Studies , DNA Primers/chemistry , DNA, Protozoan/chemistry , DNA, Protozoan/isolation & purification , Drug Combinations , Electrophoresis, Agar Gel , Female , Humans , Malaria, Falciparum/blood , Malaria, Falciparum/epidemiology , Male , Plasmodium falciparum/genetics , Polymerase Chain Reaction , Prevalence , Primaquine/therapeutic use , Pyrimethamine/therapeutic use , Reagent Kits, Diagnostic/parasitology , Sensitivity and Specificity , Sentinel Surveillance , Sulfadoxine/therapeutic use , Urban PopulationABSTRACT
Amplification, mutations, or overexpression of the pfmdr1 gene have been associated with multiple drug resistance in some strains of Plasmodium falciparum. In order to better understand this potential mechanism of drug resistance, we are currently investigating putative mdr homologues in vivo in the rodent malaria Plasmodium berghei. We have identified and partially sequenced a gene that is amplified in a MFQ-resistant (MFQr) line. Using degenerate primers, a 579-bp fragment was amplified by PCR using P. berghei genomic DNA as template. The predicted amino acid sequence shares 66% identity with the previously reported pfmdr1 gene product (Pgh1) of P. falciparum. Southern blots and slot blots of genomic DNA suggest that this gene is amplified two- to threefold in a MFQr line (N/1100), as has been previously reported in some MFQr strains of P. falciparum. The P. berghei gene was mapped to chromosome 12 in all of the lines analyzed. Furthermore, the cloned PCR product also hybridizes to chromosome 5 of the MFQr strain.
