title: High prevalence of the 437G mutation associated with sulfadoxine resistance among Plasmodium falciparum clinical isolates from Iran, three years after the introduction of sulfadoxine-pyrimethamine.
abstract: OBJECTIVE
  The objective of this study was to determine the frequency of dhfr and dhps resistance-associated haplotypes in Plasmodium falciparum isolates, three years after the introduction of sulfadoxine-pyrimethamine (SP) as the first-line antimalarial treatment in Iran.
  
  
  METHODS
  Blood samples (N=182) were collected from patients presenting with falciparum malaria from southeastern Iran, and analyzed by nested-PCR/restriction fragment length polymorphism, followed by sequencing analysis.
  
  
  RESULTS
  In pfdhfr, double mutation at positions 59R and 108N was a predominant allele with a prevalence of 95.7%. The pure double mutations of pfdhfr (I(51)N(108)) were detected, and showed an increase from 0.7% to 4.3% after the introduction of SP as first-line drug. Furthermore, a significant decrease in double mutations/wild-type of pfdhfr/pfdhps (R(59)N(108)/A(437)) was observed from 2004 (83.5%) to 2008 (44%) after changes in treatment policy. With regards to pfdhps, the results showed a rapid increase in frequency of the single pure form of pfdhps at position 437G (54.4%) and that of triple pfdhfr/pfdhps (R(59)N(108)/G(437)) mutant haplotype (51.7%) after three years.
  
  
  CONCLUSIONS
  The absence of quintuple mutations in the examined isolates supports the continued use of SP as the treatment of choice for uncomplicated malaria as a partner drug to artemisinin combination therapy in Iran. However, the increase in the triple pfdhfr/pfdhps (R(59)N(108)/G(437)) mutant haplotypes indicates that the P. falciparum parasite populations have the potential to evolve into dhfr/dhps quintuple mutants in the near future. Therefore, monitoring the status of dhps alleles as a predictor of the development of clinical resistance to sulfadoxine should be a high priority in this region.
authors.affiliation: Malaria and Vector Research Group, Biotechnology Research Center, Pasteur Institute of Iran, Pasteur Avenue, Tehran, Iran. zakeris@yahoo.com
authors.forename: Sedigheh
authors.initials: S
authors.lastname: Zakeri
authors.forename: Maryam Shahrabi
authors.initials: MS
authors.lastname: Farahani
authors.forename: Mandana
authors.initials: M
authors.lastname: Afsharpad
authors.forename: Masoud
authors.initials: M
authors.lastname: Salehi
authors.forename: Ahmad
authors.initials: A
authors.lastname: Raeisi
authors.forename: Navid Dinparast
authors.initials: ND
authors.lastname: Djadid
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019943:Amino Acid Substitution; D000962:Antimalarials / Q000627:therapeutic use*; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D016054:DNA, Protozoan / Q000235:genetics; D004094:Dihydropteroate Synthase / Q000235:genetics; D004338:Drug Combinations; D004351:Drug Resistance / Q000235:genetics; D005260:Female; D005787:Gene Frequency; D017125:Genes, Protozoan; D006239:Haplotypes; D006801:Humans; D007223:Infant; D007492:Iran; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000469:parasitology*; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D020641:Polymorphism, Single Nucleotide; D011739:Pyrimethamine / Q000627:therapeutic use*; D013413:Sulfadoxine / Q000627:therapeutic use*; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D013997:Time Factors; D055815:Young Adult
chemical_list: D000962:Antimalarials; D016054:DNA, Protozoan; D004338:Drug Combinations; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D011739:Pyrimethamine