title: Molecular monitoring of Plasmodium falciparum drug susceptibility at the time of the introduction of artemisinin-based combination therapy in Yaoundé, Cameroon: implications for the future.
abstract: BACKGROUND
  Regular monitoring of the levels of anti-malarial resistance of Plasmodium falciparum is an essential policy to adapt therapy and improve malaria control. This monitoring can be facilitated by using molecular tools, which are easier to implement than the classical determination of the resistance phenotype. In Cameroon, chloroquine (CQ), previously the first-line therapy for uncomplicated malaria was officially withdrawn in 2002 and replaced initially by amodiaquine (AQ) monotherapy. Then, artemisinin-based combination therapy (ACT), notably artesunate-amodiaquine (AS-AQ) or artemether-lumefantrine (AL), was gradually introduced in 2004. This situation raised the question of the evolution of P. falciparum resistance molecular markers in Yaoundé, a highly urbanized Cameroonian city.
  
  
  METHODS
  The genotype of pfcrt 72 and 76 and pfmdr1 86 alleles and pfmdr1 copy number were determined using real-time PCR in 447 P. falciparum samples collected between 2005 and 2009.
  
  
  RESULTS
  This study showed a high prevalence of parasites with mutant pfcrt 76 (83%) and pfmdr1 86 (93%) codons. On the contrary, no mutations in the pfcrt 72 codon and no samples with duplication of the pfmdr1 gene were observed.
  
  
  CONCLUSIONS
  The high prevalence of mutant pfcrt 76T and pfmdr1 86Y alleles might be due to the choice of alternative drugs (AQ and AS-AQ) known to select such genotypes. Mutant pfcrt 72 codon was not detected despite the prolonged use of AQ either as monotherapy or combined with artesunate. The absence of pfmdr1 multicopies suggests that AL would still remain efficient. The limited use of mefloquine or the predominance of mutant pfmdr1 86Y codon could explain the lack of pfmdr1 amplification. Indeed, this mutant codon is rarely associated with duplication of pfmdr1 gene. In Cameroon, the changes of therapeutic strategies and the simultaneous use of several formulations of ACT or other anti-malarials that are not officially recommended result in a complex selective pressure, rendering the prediction of the evolution of P. falciparum resistance difficult. This public health problem should lead to increased vigilance and regular monitoring.
authors.affiliation: Service de Parasitologie-Mycologie, Centre Hospitalier Universitaire de Toulouse et UMR152 UPS-IRD, Université de Toulouse, Toulouse, France.
authors.forename: Sandie
authors.initials: S
authors.lastname: Menard
authors.forename: Isabelle
authors.initials: I
authors.lastname: Morlais
authors.forename: Rachida
authors.initials: R
authors.lastname: Tahar
authors.forename: Collins
authors.initials: C
authors.lastname: Sayang
authors.forename: Pembe Issamou
authors.initials: PI
authors.lastname: Mayengue
authors.forename: Xavier
authors.initials: X
authors.lastname: Iriart
authors.forename: Françoise
authors.initials: F
authors.lastname: Benoit-Vical
authors.forename: Brigitte
authors.initials: B
authors.lastname: Lemen
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Magnaval
authors.forename: Parfait
authors.initials: P
authors.lastname: Awono-Ambene
authors.forename: Leonardo K
authors.initials: LK
authors.lastname: Basco
authors.forename: Antoine
authors.initials: A
authors.lastname: Berry
mesh_terms: D000293:Adolescent; D000328:Adult; D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D037621:Artemisinins / Q000494:pharmacology / Q000627:therapeutic use*; D002163:Cameroon; D002648:Child; D002675:Child, Preschool; D016054:DNA, Protozoan / Q000235:genetics; D004351:Drug Resistance; D004359:Drug Therapy, Combination / Q000379:methods; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000469:parasitology*; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics; D008875:Middle Aged; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D020125:Mutation, Missense; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics*; D015995:Prevalence; D015800:Protozoan Proteins / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D018571:Sentinel Surveillance; D055815:Young Adult
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D016054:DNA, Protozoan; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D015800:Protozoan Proteins; C513498:Mdr1 protein, Plasmodium falciparum; C416369:PfCRT protein, Plasmodium falciparum; C031327:artemisinin