title: Molecular markers in plasmodium falciparum linked to resistance to anti-malarial drugs in samples imported from Africa over an eight-year period (2002-2010): impact of the introduction of artemisinin combination therapy.
abstract: BACKGROUND
  Drug resistance is a major problem to control Plasmodium falciparum infection in endemic countries. During last decade, African countries have changed first-line treatment to artemisinin-based combinations therapy (ACT); sulphadoxine-pyrimethamine (SP) is recommended for Intermittent Preventive Therapy (IPT). Molecular markers related to P falciparum resistance were analysed for the period of transition from SP to ACT, in isolates imported from Africa.
  
  
  METHODS
  A first group of samples was taken in the period between June 2002 and June 2006 (n = 113); a second group in the period between November 2008 and August 2010 (n = 46). Several alleles were analysed by nested PCR-RFLP: 51, 59, 108, 164, in the pfdhfr gene; 436, 437, 540, 581, in the pfdhps gene; 86, 1246, in the pfmdr1 gene and 76, in the pfcrt gene. The prevalence of alleles in the groups was compared with the chi-squared or Fisher's exact tests.
  
  
  RESULTS
  The pfdhfr N51I, C59R and S108N were over to 90% in the two groups; all samples had the I164. In the pfdhps, 437 G and 581 G, increased up to 80% and 10.9% (p = 0.024), respectively in the second group. The 540 G decreases (24% to 16.%) and the 436A disappears at the end of the follow-up (p = 0.004) in the second group. The 76I-pfcrt stayed over 95% in the two groups. Prevalence of 86Y-pfmdr1 decreased over eight years.
  
  
  CONCLUSIONS
  Pharmacological pressure affects the resistance strains prevalence. As for SP, the disappearance of 436A and the decrease in 540 G suggest that these mutations are not fixed. On the other hand, studies carried out after ACT introduction show there was a selection of strains carrying the SNPs N86Y, D1246Y in pfmdr1. In this work, the prevalence of pfmdr1- D1246Y is increasing, perhaps as a result of selective pressure by ACT. Continued surveillance is essential to monitor the effectiveness of treatments.
authors.affiliation: Department of Microbiology and Parasitology, Hospital Carlos III, Madrid 28029, Spain. aranchazu@gmail.com
authors.forename: Aranzazu
authors.initials: A
authors.lastname: Amor
authors.forename: Carlos
authors.initials: C
authors.lastname: Toro
authors.forename: Amalia
authors.initials: A
authors.lastname: Fernández-Martínez
authors.forename: Margarita
authors.initials: M
authors.lastname: Baquero
authors.forename: Agustín
authors.initials: A
authors.lastname: Benito
authors.forename: Pedro
authors.initials: P
authors.lastname: Berzosa
mesh_terms: D000349:Africa; D000483:Alleles; D000818:Animals; D000962:Antimalarials / Q000008:administration & dosage / Q000494:pharmacology*; D037621:Artemisinins / Q000008:administration & dosage / Q000494:pharmacology; D016054:DNA, Protozoan / Q000235:genetics; D004338:Drug Combinations; D004351:Drug Resistance; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D050505:Mutant Proteins / Q000235:genetics; D020125:Mutation, Missense; D010453:Peptide Synthases / Q000235:genetics; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011739:Pyrimethamine / Q000008:administration & dosage / Q000494:pharmacology; D013413:Sulfadoxine / Q000008:administration & dosage / Q000494:pharmacology; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D014195:Travel
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D016054:DNA, Protozoan; D004338:Drug Combinations; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D050505:Mutant Proteins; D010453:Peptide Synthases; D011739:Pyrimethamine; D013413:Sulfadoxine; D013762:Tetrahydrofolate Dehydrogenase; C513498:Mdr1 protein, Plasmodium falciparum; C001205:fanasil, pyrimethamine drug combination; C031327:artemisinin; C020041:dihydrofolate synthetase