Minority-Variant pfcrt K76T Mutations and Chloroquine Resistance, Malawi

摘要

Genotyping of the chloroquine-resistance biomarker pfcrt (Plasmodium falciparumchloroquine resistance trans-porter gene) suggests that, in the absence of chloroquine pressure, Plasmodium falciparumparasites in Malawi have reverted to chloroquine sensitivity. However, malaria infec-tions in Africa are commonly polyclonal, and standard PCRs cannot detect minority genotypes if present in <20% of the parasites in an individual host. We have developed a mul-tiple site–specifi c heteroduplex tracking assay (MSS-HTA) that can detect pfcrt 76T mutant parasites consisting of as little as 1% of the parasite population. In clinical samples, no pfcrt 76T was detected in 87 pregnant Malawian women by standard PCR. However, 22 (25%) contained minority-vari-ant resistant genotypes detected by the MSS-HTA. These results were confi rmed by subcloning and sequencing. This fi nding suggests that the chloroquine-resistant genotype re-mains common in Malawians and that PCR-undetectable drug-resistant genotypes may be present in disease-en-demic populations. Surveillance for minority-variant drug-resistant mutations may be useful in making antimalarial drug policy.