title: Temporal trends of sulphadoxine-pyrimethamine (SP) drug-resistance molecular markers in Plasmodium falciparum parasites from pregnant women in western Kenya.
abstract: BACKGROUND
  Resistance to sulphadoxine-pyrimethamine (SP) in Plasmodium falciparum parasites is associated with mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes and has spread worldwide. SP remains the recommended drug for intermittent preventive treatment for malaria in pregnancy (IPTp) and information on population prevalence of the SP resistance molecular markers in pregnant women is limited.
  
  
  METHODS
  Temporal trends of SP resistance molecular markers were investigated in 489 parasite samples collected from pregnant women at delivery from three different observational studies between 1996 and 2009 in Kenya, where SP was adopted for both IPTp and case treatment policies in 1998. Using real-time polymerase chain reaction, pyrosequencing and direct sequencing, 10 single-nucleotide polymorphisms (SNPs) of SP resistance molecular markers were assayed.
  
  
  RESULTS
  The prevalence of quintuple mutant (dhfr N51I/C59R/S108N and dhps A437G/K540E combined genotype) increased from 7% in the first study (1996-2000) to 88% in the third study (2008-2009). When further stratified by sample collection year and adoption of IPTp policy, the prevalence of the quintuple mutant increased from 2.4% in 1998 to 44.4% three years after IPTp policy adoption, seemingly in parallel with the increase in percentage of SP use in pregnancy. However, in the 1996-2000 study, more mutations in the combined dhfr/dhps genotype were associated with SP use during pregnancy only in univariable analysis and no associations were detected in the 2002-2008 and 2008-2009 studies. In addition, in the 2008-2009 study, 5.3% of the parasite samples carried the dhps triple mutant (A437G/K540E/A581G). There were no differences in the prevalence of SP mutant genotypes between the parasite samples from HIV + and HIV- women over time and between paired peripheral and placental samples.
  
  
  CONCLUSIONS
  There was a significant increase in dhfr/dhps quintuple mutant and the emergence of new genotype containing dhps 581 in the parasites from pregnant women in western Kenya over 13 years. IPTp adoption and SP use in pregnancy only played a minor role in the increased drug-resistant parasites in the pregnant women over time. Most likely, other major factors, such as the high prevalence of resistant parasites selected by the use of SP for case management in large non-pregnant population, might have contributed to the temporally increased prevalence of SP resistant parasites in pregnant women. Further investigations are needed to determine the linkage between SP drug resistance markers and efficacy of IPTp-SP.
authors.affiliation: Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30329-4018, USA.
authors.forename: Nnaemeka C
authors.initials: NC
authors.lastname: Iriemenam
authors.forename: Monica
authors.initials: M
authors.lastname: Shah
authors.forename: Wangeci
authors.initials: W
authors.lastname: Gatei
authors.forename: Anna M
authors.initials: AM
authors.lastname: van Eijk
authors.forename: John
authors.initials: J
authors.lastname: Ayisi
authors.forename: Simon
authors.initials: S
authors.lastname: Kariuki
authors.forename: Jodi
authors.initials: J
authors.lastname: Vanden Eng
authors.forename: Simon O
authors.initials: SO
authors.lastname: Owino
authors.forename: Ashima A
authors.initials: AA
authors.lastname: Lal
authors.forename: Yusuf O
authors.initials: YO
authors.lastname: Omosun
authors.forename: Kephas
authors.initials: K
authors.lastname: Otieno
authors.forename: Meghna
authors.initials: M
authors.lastname: Desai
authors.forename: Feiko O
authors.initials: FO
authors.lastname: ter Kuile
authors.forename: Bernard
authors.initials: B
authors.lastname: Nahlen
authors.forename: Julie
authors.initials: J
authors.lastname: Moore
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Hamel
authors.forename: Peter
authors.initials: P
authors.lastname: Ouma
authors.forename: Laurence
authors.initials: L
authors.lastname: Slutsker
authors.forename: Ya Ping
authors.initials: YP
authors.lastname: Shi
mesh_terms: D000328:Adult; D000962:Antimalarials / Q000494:pharmacology*; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004094:Dihydropteroate Synthase / Q000235:genetics; D004338:Drug Combinations; D004351:Drug Resistance; D005260:Female; D005838:Genotype; D006801:Humans; D007630:Kenya; D016778:Malaria, Falciparum / Q000469:parasitology*; D020125:Mutation, Missense; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics*; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000469:parasitology*; D015800:Protozoan Proteins / Q000235:genetics; D011739:Pyrimethamine / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D013413:Sulfadoxine / Q000494:pharmacology*; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics
chemical_list: D000962:Antimalarials; D016054:DNA, Protozoan; D004338:Drug Combinations; D015800:Protozoan Proteins; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase; D011739:Pyrimethamine