High‐Level Chloroquine Resistance in Sudanese Isolates of<i>Plasmodium falciparum</i>Is Associated with Mutations in the Chloroquine Resistance Transporter Gene<i>pfcrt</i>and the Multidrug Resistance Gene<i>pfmdr1</i>

Polymorphisms were examined in 2 Plasmodium falciparum genes, as were chloroquine responses of clones and isolates from a village in eastern Sudan. There was a significant association between an allele of the P. falciparum chloroquine resistance transporter gene (pfcrt-T76) and both in vitro and in vivo resistance. There was a less significant association with the multidrug resistance gene pfmdr1-Y86 allele. A significant association between pfmdr1-Y86 and pfcrt-T76 was apparent among resistant isolates, which suggests a joint action of the 2 genes in high-level chloroquine resistance.