Association of pfcrt but not pfmdr1 alleles with chloroquine resistance in Iranian isolates of Plasmodium falciparum.

This study was designed to analyze the Plasmodium falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) mutations as markers of chloroquine (CQ) resistance in 200 blood samples collected from malaria patients in south-eastern Iran during 2002-2005. Among these, 25 (post-treatment) fulfilled the 28-day follow-up study. A high number of Iranian P. falciparum (97%) strains harbored quadruple mutations at codons 76T, 220S, 326D, and 356L. All post-treatment isolates harbored the mutant allele 76T, but low rates of the mutant allele 86Y (44%) of the pfmdr1 gene were detected. No wild haplotype of pfcrt (72-CVMNKAQNIR-371) was found in post-treatment samples; however, 56% of clinical "failure" samples carried the wild type of pfmdr1 (NYSND). The present results suggest a strong association between pfcrt 76T, but not pfmdr1 86Y mutation and in vivo CQ resistance. Furthermore, we found the CQ resistance-associated SVMNT haplotype, which previously had been seen in South American isolates. Although Iran is located more proximally to Southeast Asia than to South America, no CQ resistance-associated CVIET haplotye has been observed in this region. Therefore, these results were not consistent with the earlier presumed spread of CQR parasites from Southeast Asia to Africa via the Indian subcontinent. In conclusion, P. falciparum mutations associated with resistance to CQ are abundant in south-eastern Iran and this finding strongly supports that CQ as the first line drug is inadequate for treatment of uncomplicated falciparum malaria in Iran.