Molecular assessment of drug resistance in Plasmodium falciparum from Bahr El Gazal province, Sudan

Abstract

Aims: To assess resistance to chloroquine (CQ) and sulphadoxine/pyrimethamine (SP) in a Sudanese parasite population.

Methods: Recurrent security problems in Akuem, Sudan, prevented us from conducting a classical in vivo treatment efficacy study. Instead we genotyped key mutations in the chloroquine resistance transporter (pfcrt), the multidrug resistance gene (pfmdr1), dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps). We genotyped the K76T mutation in pfcrt and the N86Y mutation in (pfmdr) by restriction digestion of fluorescent end-labelled polymerase chain reaction (PCR) products, while we genotyped codons 16, 51, 59, 108 and 164 in dhfr and codons 436, 437, 540, 581 and 613 in dhps by primer extension in 100 blood samples.

Results: Sixty-three percent of parasites carried the 76T mutation at pfcrt critical for CQ resistance, while 31% carried the 86Y mutation at pfmdr that is associated with, although not essential, for CQ resistance. We found five dhfr alleles: 60% of infections contained wild-type dhfr alleles, 3% had one mutation, 34% had two mutations, while 3% had three mutations. We found three dhps alleles: 47% were wild type, 44% had one mutation, while 9% had two mutations.

Conclusions: We expect high levels of treatment failure (RI-RIII) with CQ (20-40%) and predict efficient treatment with SP. However, dhfr alleles with three mutations (51I, 59R, 108N) are present as are dhps alleles with two mutations (437G, 540E). Successful treatment with SP is therefore likely to be short-lived.