Emergence of an unusual sulfadoxine-pyrimethamine resistance pattern and a novel K540N mutation in dihydropteroate synthetase in Plasmodium falciparum isolates obtained from Car Nicobar Island, India, after the 2004 Tsunami.
ABSTRACT Enormous amounts of drugs were used to contain the outbreak of infectious diseases in areas of India affected by the tsunami in December 2004. The impact of this drug use on the Plasmodium falciparum population needs to be investigated.
The nucleotide sequence of the pfcrt, pfdhps, and pfdhfr genes was determined for 229 clinical P. falciparum isolates collected from patients on Car Nicobar Island at 6 different time points between May 2004 and May 2008.
Over time, there was an increase in the proportion of the P. falciparum population that had mutations in the pfcrt, pfdhps, and pfdhfr genes associated with higher levels of chloroquine, sulfadoxine, and pyrimethamine resistance, respectively. However, the parasites collected during October 2005 had mutations associated with a lower level of pyrimethamine resistance and a higher level of sulfadoxine resistance (a rare combination), as well as a novel K540N mutation in P. falciparum dihydropteroate synthetase (PfDHPS). The emergence of this parasite population coincided with the widespread use of an additional antifolate drug, trimethoprim-sulfamethoxazole, to treat other infections during January- March 2005. Molecular modeling revealed that the sulfadoxine binding affinity of the new PfDHPS triple mutant A436G437N540A581A613 was similar to that of A436G437E540A581A613 (bold type indicates mutated amino acids).
The use of 2 antifolate drugs in combination should be avoided to prevent the selection of parasites with newer mutations and altered drug susceptibilities
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ABSTRACT: The Thailand-Cambodia border is the epicenter for drug-resistant falciparum malaria. Previous studies have shown that chloroquine (CQ) and pyrimethamine resistance originated in this region and eventually spread to other Asian countries and Africa. However, there is a dearth in understanding the origin and evolution of dhps alleles associated with sulfadoxine resistance. The present study was designed to reveal the origin(s) of sulfadoxine resistance in Cambodia and its evolutionary relationship to African and South American dhps alleles. We sequenced 234 Cambodian Plasmodium falciparum isolates for the dhps codons S436A/F, A437G, K540E, A581G and A613S/T implicated in sulfadoxine resistance. We also genotyped 10 microsatellite loci around dhps to determine the genetic backgrounds of various alleles and compared them with the backgrounds of alleles prevalent in Africa and South America. In addition to previously known highly-resistant triple mutant dhps alleles SGEGA and AGEAA (codons 436, 437, 540, 581, 613 are sequentially indicated), a large proportion of the isolates (19.3%) contained a 540N mutation in association with 437G/581G yielding a previously unreported triple mutant allele, SGNGA. Microsatellite data strongly suggest the strength of selection was greater on triple mutant dhps alleles followed by the double and single mutants. We provide evidence for at least three independent origins for the double mutants, one each for the SGKGA, AGKAA and SGEAA alleles. Our data suggest that the triple mutant allele SGEGA and the novel allele SGNGA have common origin on the SGKGA background, whereas the AGEAA triple mutant was derived from AGKAA on multiple, albeit limited, genetic backgrounds. The SGEAA did not share haplotypes with any of the triple mutants. Comparative analysis of the microsatellite haplotypes flanking dhps alleles from Cambodia, Kenya, Cameroon and Venezuela revealed an independent origin of sulfadoxine resistant alleles in each of these regions.PLoS Pathogens 01/2010; 6(3):e1000830. · 9.13 Impact Factor