Open AccessCommon Origin and Fixation of Plasmodium falciparum dhfr and dhps Mutations Associated with Sulfadoxine-Pyrimethamine Resistance in a Low-Transmission Area in South America
Author(s) -
Andrea M. McCollum,
Kristen L. Mueller,
Leopoldo Villegas,
Venkatachalam Udhayakumar,
Ananías A. Escalante
Publication year - 2007
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.01228-06
Subject(s) - dhps , biology , dihydropteroate synthase , genetics , population , dihydrofolate reductase , sulfadoxine , allele , microsatellite , pyrimethamine , plasmodium falciparum , virology , gene , malaria , immunology , medicine , environmental health
Recent studies indicated that sensitive parasites could increase in frequency in a population when drugs are removed, suggesting that the life span of affordable antimalarial drugs could be expanded. We studied 97 samples from Bolivar State, Venezuela, an area where sulfadoxine-pyrimethamine (SP) has not been used for 8 years due to its ineffectiveness. We characterized point mutations in two genes that have been implicated in resistance to SP, dihydrofolate reductase (dhfr ) and dihydropteroate synthase (dhps ). We also assayed neutral microsatellite markers around thedhfr (chromosome 4) anddhps (chromosome 8) genes and on chromosomes 2 and 3 to track the origin and spread of resistant alleles. We found that drug-resistant SP mutants are fixed in the population. Two genotypes were present in the samples,dhfr (50R /51I /108N )dhps (437G /540E /581G ) (90.7%) anddhfr (51I /108N )dhps (437G /581G ) (9.3%). We show a single microsatellite haplotype for all of thedhfr anddhps alleles, and the alleles at the microsatellite loci are different from those present in Africa. Thus, in these samples from Venezuela, there is a single origin for bothdhfr anddhps SP-resistant alleles, and these alleles originated independently of those characterized from Africa. Furthermore, this is the first report of a “hitchhiking effect” on the genetic variation arounddhps due to selection by SP using an extensive set of microsatellite markers. Our results indicate that, in areas where there is limited gene flow, the fixation of drug-resistant parasites in the population is stable, even after drug selection is relaxed.