Evaluation of dihydrofolate reductase and dihydropteroate synthetase genotypes that confer resistance to sulphadoxine-pyrimethamine in Plasmodium falciparum in Haiti

Abstract

BackgroundMalaria caused by Plasmodium falciparum infects roughly 30,000 individuals in Haiti each year. Haiti has used chloroquine (CQ) as a first-line treatment for malaria for many years and as a result there are concerns that malaria parasites may develop resistance to CQ over time. Therefore it is important to prepare for alternative malaria treatment options should CQ resistance develop. In many other malaria-endemic regions, antifolates, particularly pyrimethamine (PYR) and sulphadoxine (SDX) treatment combination (SP), have been used as an alternative when CQ resistance has developed. This study evaluated mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) genes that confer PYR and SDX resistance, respectively, in P. falciparum to provide baseline data in Haiti. This study is the first comprehensive study to examine PYR and SDX resistance genotypes in P. falciparum in Haiti.MethodsDNA was extracted from dried blood spots and genotyped for PYR and SDX resistance mutations in P. falciparum using PCR and DNA sequencing methods. Sixty-one samples were genotyped for PYR resistance in codons 51, 59, 108 and 164 of the dhfr gene and 58 samples were genotyped for SDX resistance codons 436, 437, 540 of the dhps gene in P. falciparum.ResultsThirty-three percent (20/61) of the samples carried a mutation at codon 108 (S108N) of the dhfr gene. No mutations in dhfr at codons 51, 59, 164 were observed in any of the samples. In addition, no mutations were observed in dhps at the three codons (436, 437, 540) examined. No significant difference was observed between samples collected in urban vs rural sites (Welch’s T-test p-value = 0.53 and permutations p-value = 0.59).ConclusionThis study has shown the presence of the S108N mutation in P. falciparum that confers low-level PYR resistance in Haiti. However, the absence of SDX resistance mutations suggests that SP resistance may not be present in Haiti. These results have important implications for ongoing discussions on alternative malaria treatment options in Haiti.

Plasmodium falciparum Drug-Resistant Haplotypes and Population Structure in Postearthquake Haiti, 2010

“…[29][30][31][32] In addition, we did not find any sulfadoxine-resistant mutations in pfdhps, with the exception of those reported for HH14, consistent with reports of no pfdhps in mutations in a study from Carter and others. 28 Therefore, this single isolate with a CVIET-CQresistant haplotype, triple pfdhfr mutations, and double pfdhps mutations differs greatly from all the other specimens in our study and from the majority of specimens in other recent reports from Haiti. 7,8,27,28 This pattern of drug-resistant mutations is reminiscent of P. falciparum pfcrt-CVIET populations found in sub-Saharan Africa and southeast Asia.…”

“…27,28 The remainders of the parasite samples were wildtype for pfdhfr except for specimen HH14. The S108N mutation in pfdhfr is frequently selected when SP is first used and can confer low-level resistance to pyrimethamine.…”

Artemisinin Resistance-Associated Polymorphisms at the K13-Propeller Locus are Absent in Plasmodium falciparum Isolates from Haiti

“…Low genetic variation observed at the K13-propeller mirrors the results of investigations into other antimalarial resistance-associated loci in Haiti, including dhfr, dhps, pfcrt, and pfmdr, 15,18 supporting the idea that Haiti's P. falciparum population has low genetic variation at antimalarial resistance-associated genes.…”

“…Details about the collection of these samples have been discussed previously. 15,18 Terre Noire is considered an urban region, whereas Leogane, Jacmel, Chabin, Hinche, North Cap Haitian, and Nippes are more rural. Although malaria transmission in Haiti is low overall, there have been reports of transmission hotspots in the Southeast Department (which includes Jacmel and Chabin), particularly near coastal areas.…”

“…15,16 Although pyrimethamine resistance was reported in an in vitro study from 1984, 17 a recent molecular study reported only the pfdhfr S108N lowlevel pyrimethamine resistance mutation and no sulfadoxine resistance-associated mutations in the pfdhps in Haiti. 18 Currently, chloroquine remains the first-line treatment for malaria in Haiti. However, ACTs are likely candidates to replace chloroquine in the future should chloroquine resistance emerge in Haiti.…”