CHLOROQUINE-RESISTANT ISOLATES OF PLASMODIUM FALCIPARUM WITH ALTERNATIVE CG2 REPEAT LENGTH POLYMORPHISMS

Abstract. A particular polymorphism in the cg2 gene has previously been linked to chloroquine resistance in reference isolates of Plasmodium falciparum. To assess the association of this polymorphism with chloroquine resis-tance in field specimens of P. falciparum, we analyzed the repeat region of the cg2 gene in 47 isolates of P. falciparum collected in the Ingwavuma District of northern KwaZulu-Natal, South Africa. Polymerase chain reaction (PCR) primers, which were designed to amplify the region of DNA surrounding the repeat, were used to obtain repeat PCR products from the field isolates. The PCR product for each isolate varied in length, depending on the number of cg2 repeats for that isolate. We found that several in vivo and in vitro chloroquine-resistant isolates of P. falciparum did not have the expected 16 repeats. These results suggest that the link between the cg2 polymor-phism and chloroquine resistance identified previously may not apply in all malarious areas. To help restrict the occurrence and spread of drug-resistant malaria, it is necessary to monitor drug efficacy in malarious regions of the world.1 Standard in vivo and in vitro chloro-quine sensitivity tests restrict sample eligibility for a number of reasons. For example, patients should have had no ex-posure to antimalarials or antibiotics in the 14 days prior t