title: DHFR and DHPS genotypes of Plasmodium falciparum isolates from Gabon correlate with in vitro activity of pyrimethamine and cycloguanil, but not with sulfadoxine-pyrimethamine treatment efficacy.
abstract: OBJECTIVE
  To assess the relationship between the presence of DHFR and DHPS mutations in Plasmodium falciparum, parasite in vitro resistance, and in vivo efficacy of sulfadoxine-pyrimethamine (SP) treatment.
  
  
  METHODS
  Measurement of SP treatment efficacy in malaria-infected children in Gabon was combined with in vitro tests of susceptibility to pyrimethamine and cycloguanil, and molecular genotyping at several DHFR and DHPS loci of parasites isolated before treatment. DHFR was studied at codons 108, 51, and 59, whereas DHPS gene was typed at positions 436, 437, 540 and 581.
  
  
  RESULTS
  SP treatment was effective in 86% of children by day 28. Seventy-five percent of isolates were in vitro resistant to pyrimethamine and 65.5% to cycloguanil. No mutation was detected at codons 540 and 581 of the DHPS gene. Most isolates (71.8%) presented with the triple mutant DHFR genotype, whereas 64.3% combined at least three DHFR and one DHPS mutations. The increase in the number of DHFR mutations was associated with an increase in in vitro resistance to pyrimethamine and cycloguanil; three DHFR mutations conferred pyrimethamine and to a lesser extent cycloguanil resistance. Treatment failures only occurred with isolates presenting at least two DHFR mutations (S108N and C59R) and one DHPS mutation (S436A or A437G), but SP treatment of infections with such parasites gave treatment success in 82.0% of children.
  
  
  CONCLUSIONS
  DHFR mutations that lead to high-level in vitro resistance to pyrimethamine plus 1-2 DHPS mutations are not sufficient to induce in vivo failure of SP treatment in young children from Gabon.
authors.affiliation: Centre International de Recherches Médicales de Franceville, Unité de Parasitologie Médicale, BP 769 Franceville.
authors.forename: Agnès
authors.initials: A
authors.lastname: Aubouy
authors.forename: Sayeh
authors.initials: S
authors.lastname: Jafari
authors.forename: Virginie
authors.initials: V
authors.lastname: Huart
authors.forename: Florence
authors.initials: F
authors.lastname: Migot-Nabias
authors.forename: Justice
authors.initials: J
authors.lastname: Mayombo
authors.forename: Rémy
authors.initials: R
authors.lastname: Durand
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bakary
authors.forename: Jacques
authors.initials: J
authors.lastname: Le Bras
authors.forename: Philippe
authors.initials: P
authors.lastname: Deloron
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D016054:DNA, Protozoan / Q000235:genetics / Q000302:isolation & purification; D004094:Dihydropteroate Synthase / Q000235:genetics*; D005681:Gabon; D005838:Genotype; D006801:Humans; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D002727:Proguanil; D011739:Pyrimethamine / Q000494:pharmacology*; D013413:Sulfadoxine / Q000494:pharmacology*; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D014227:Triazines / Q000494:pharmacology*
chemical_list: D000962:Antimalarials; D016054:DNA, Protozoan; D014227:Triazines; C026009:cycloguanil; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D002727:Proguanil; D011739:Pyrimethamine