title: A SYBR Green 1-based in vitro test of susceptibility of Ghanaian Plasmodium falciparum clinical isolates to a panel of anti-malarial drugs.
abstract: BACKGROUND
  Based on report of declining efficacy of chloroquine, Ghana shifted to the use of artemisinin-based combination therapy (ACT) in 2005 as the first-line anti-malarial drug. Since then, there has not been any major evaluation of the efficacy of anti-malarial drugs in Ghana in vitro. The sensitivity of Ghanaian Plasmodium falciparum isolates to anti-malarial drugs was, therefore, assessed and the data compared with that obtained prior to the change in the malaria treatment policy.
  
  
  METHODS
  A SYBR Green 1 fluorescent-based in vitro drug sensitivity assay was used to assess the susceptibility of clinical isolates of P. falciparum to a panel of 12 anti-malarial drugs in three distinct eco-epidemiological zones in Ghana. The isolates were obtained from children visiting health facilities in sentinel sites located in Hohoe, Navrongo and Cape Coast municipalities. The concentration of anti-malarial drug inhibiting parasite growth by 50% (IC50) for each drug was estimated using the online program, ICEstimator.
  
  
  RESULTS
  Pooled results from all the sentinel sites indicated geometric mean IC50 values of 1.60, 3.80, 4.00, 4.56, 5.20, 6.11, 10.12, 28.32, 31.56, 93.60, 107.20, and 8952.50 nM for atovaquone, artesunate, dihydroartemisin, artemether, lumefantrine, amodiaquine, mefloquine, piperaquine, chloroquine, tafenoquine, quinine, and doxycycline, respectively. With reference to the literature threshold value indicative of resistance, the parasites showed resistance to all the test drugs except the artemisinin derivatives, atovaquone and to a lesser extent, lumefantrine. There was nearly a two-fold decrease in the IC50 value determined for chloroquine in this study compared to that determined in 2004 (57.56 nM). This observation is important, since it suggests a significant improvement in the efficacy of chloroquine, probably as a direct consequence of reduced drug pressure after cessation of its use. Compared to that measured prior to the change in treatment policy, significant elevation of artesunate IC50 value was observed. The results also suggest the existence of possible cross-resistance among some of the test drugs.
  
  
  CONCLUSIONS
  Ghanaian P. falciparum isolates, to some extent, have become susceptible to chloroquine in vitro, however the increasing trend in artesunate IC50 value observed should be of concern. Continuous monitoring of ACT in Ghana is recommended.
authors.affiliation: Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, Accra, Ghana. nquashie@noguchi.ug.edu.gh.
authors.forename: Neils B
authors.initials: NB
authors.lastname: Quashie
authors.forename: Nancy O
authors.initials: NO
authors.lastname: Duah
authors.forename: Benjamin
authors.initials: B
authors.lastname: Abuaku
authors.forename: Lydia
authors.initials: L
authors.lastname: Quaye
authors.forename: Ruth
authors.initials: R
authors.lastname: Ayanful-Torgby
authors.forename: George A
authors.initials: GA
authors.lastname: Akwoviah
authors.forename: Margaret
authors.initials: M
authors.lastname: Kweku
authors.forename: Jacob D
authors.initials: JD
authors.lastname: Johnson
authors.forename: Naomi W
authors.initials: NW
authors.lastname: Lucchi
authors.forename: Venkatachalam
authors.initials: V
authors.lastname: Udhayakumar
authors.forename: Christopher
authors.initials: C
authors.lastname: Duplessis
authors.forename: Karl C
authors.initials: KC
authors.lastname: Kronmann
authors.forename: Kwadwo A
authors.initials: KA
authors.lastname: Koram
mesh_terms: D000962:Antimalarials / Q000494:pharmacology*; D052160:Benzothiazoles; D002648:Child; D002675:Child, Preschool; D002738:Chloroquine / Q000494:pharmacology; D003959:Diamines; D004351:Drug Resistance; D005869:Ghana; D006801:Humans; D007223:Infant; D020128:Inhibitory Concentration 50; D016778:Malaria, Falciparum / Q000469:parasitology*; D009930:Organic Chemicals / Q000737:chemistry*; D010963:Plasmodium falciparum / Q000187:drug effects*; D011804:Quinolines
chemical_list: D000962:Antimalarials; D052160:Benzothiazoles; D003959:Diamines; D009930:Organic Chemicals; D011804:Quinolines; C098022:SYBR Green I; D002738:Chloroquine