JAC Advance Access originally published online on June 12, 2003
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Journal of Antimicrobial Chemotherapy (2003) 52, 43-49
© 2003 The British Society for Antimicrobial Chemotherapy
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
1 Centre International de Recherches Médicales de Franceville, Unité de Parasitologie Médicale, BP 769 Franceville; 4 Bakoumba Hospital, BP52, Bakoumba, Gabon; 2 Hôpital Bichat-Claude Bernard, Laboratoire de Parasitologie, 46 rue Henri Huchard, 75877 Paris; 5 IRD UR010, Faculté de Pharmacie, Laboratoire de Parasitologie, 4 Avenue de l’Observatoire, 75006 Paris, France; 3 Institut de Recherche pour le Développement (IRD), UR010, Mother and Child Health in the Tropics, BP1386, Dakar, Senegal
Received 25 September 2002; returned 7 March 2003; revised 17 March 2003; accepted 22 April 2003
Objectives: 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.
Patients and 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.
Keywords: malaria, drug resistance, antifolates, molecular markers
* Corresponding author. Tel: +33-1-53-73-96-21; Fax: +33-1-42-16-26-54; E-mail: Philippe.Deloron{at}ird.fr
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