Short report: differences in dihydrofolate reductase but not dihydropteroate synthase alleles in Plasmodium falciparum isolates from geographically distinct areas in Malaysia.

Abstract

Abstract. Dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr) alleles were typed in 67 Malaysian Plasmodium falciparum isolates. The isolates were collected from two geographically distinct locations: 51 from Sabah, Malaysian Borneo, where sulfadoxine/pyrimethamine (SDX/PYR) is used to treat uncomplicated malaria and 16 from Peninsular Malaysia where in vivo resistance to SDX/PYR has been reported. A total of seven dhps alleles were identified with no significant difference in allele frequency between the 2 populations. Two of the dhps alleles described here have not been previously reported. Four dhfr alleles were detected in 67 P. falciparum isolates. Eightyseven percent of the isolates from the Peninsula, where clinical SDX/PYR failure has been reported, had dhfr alleles with triple point mutations while all of the isolates from Sabah had dhfr alleles with 2 or less point mutations. The difference in dhfr allele frequency between the two populations was highly significant. There was no correlation between in vitro PYR response and accumulation of dhfr point mutations.

Mutational analysis of Plasmodium falciparum dihydrofolate reductase and dihydropteroate synthase genes in the interior division of Sabah, Malaysia

“…Three different alleles, namely ANRNL, ANRNI and AIRNI were detected (Table 2a). The most prevalent allele in this study is ANRNL (86.4%), which was absent in previous study conducted in Sabah about 15 years ago [4]. All isolates had mutation at position S108N and C59R accompanied by 86.4% (n = 19) mutation at I164L.…”

“…In vitro resistance of P. falciparum to PYR is primarily conferred by a non-synonymous point mutation at S108N and is progressively enhanced by mutations at residue N51I and/or C59R of pfdhfr . An additional mutation at I164L is associated with high-level clinical resistance to SDX/PYR [4,5]. In pfdhps , point mutations at A437G and K540E are considered responsible for SDX resistance.…”

“…A subsequent molecular study reported 87% of P. falciparum had triple mutations in pfdhfr and all isolates having point mutation at codon A437G of pfdhps as indication of drug pressure, accompanied by 81% point mutation at codon A581G indicating reduced in vitro responsiveness of SDX [4]. The authors speculated that SDX/PYR might be still effective in treating uncomplicated P. falciparum malaria in Sabah due to most of the isolates having two or less dhfr mutations.…”

Treatment of Uncomplicated Falciparum Malaria in Southern Vietnam: Can Chloroquine or Sulfadoxine-Pyrimethamine Be Reintroduced in Combination with Artesunate?

“…The role of dhfr mutations was weaker in group 2 patients than was that of pfcrt in group 1 patients. Although we found no significant associations between dhfr mutations and clinical response in group 2, we found that I164L, the mutation most predictive of clinical failure [14,15], was more prevalent in Binh Phuoc than Dac Lac, and there was a trend to its selection with treatment in Binh Phuoc. In addition, available isolates from group 2 patients (mostly from Binh Phuoc) with PCRconfirmed recrudescence had significantly higher pyrimethamine-sulfadoxine IC 50 values than did those isolates obtained from patients who were cured.…”

“…Reactions indicating the presence of both mutant and wild type alleles were reconfirmed under stringent digestion conditions. Similar methods were used to detect the dihydrofolate reductase (pfdhfr ) mutations N51I, C59R, S108N, and I164L [14][15][16]. The oligonucleotide primer pairs used for multilocus genotyping and for pfcrt and pfdhfr allelic typing did not amplify the P. vivax DNA that was included as a control in all assays.…”