Plasmodium falciparum sulfadoxine resistance is geographically and genetically clustered within the DR Congo

Abstract

Understanding the spatial clustering of Plasmodium falciparum populations can assist efforts to contain drug-resistant parasites and maintain the efficacy of future drugs. We sequenced single nucleotide polymorphisms (SNPs) in the dihydropteroate synthase gene (dhps) associated with sulfadoxine resistance and 5 microsatellite loci flanking dhps in order to investigate the genetic backgrounds, genetic relatedness, and geographic clustering of falciparum parasites in the Democratic Republic of the Congo (DRC). Resistant haplotypes were clustered into subpopulations: one in the northeast DRC, and the other in the balance of the DRC. Network and clonal lineage analyses of the flanking microsatellites indicate that geographically-distinct mutant dhps haplotypes derive from separate lineages. The DRC is therefore a watershed for haplotypes associated with sulfadoxine resistance. Given the importance of central Africa as a corridor for the spread of antimalarial resistance, the identification of the mechanisms of this transit can inform future policies to contain drug-resistant parasite strains.

Multilocus Microsatellite Genotyping Array for Investigation of Genetic Epidemiology of Pneumocystis jirovecii

“…In contrast, the isolates from Spain, which were largely sulfa naive and which harbored primarily wild-type dhps haplotypes, demonstrated a higher heterozygosity at this dhps-linked locus (H e ϭ 0.632). Taken together with evidence that antibiotic pressure causes changes in dhps mutant genotype frequency (73), this pattern is consistent with a selective sweep occurring around the dhps locus due to drug pressure, as has been observed in pathogens such as Plasmodium falciparum (36). In order to confirm this, further studies will require additional markers near the dhps locus and greater numbers of isolates bearing wild-type and mutant dhps haplotypes.…”

“…Microsatellites are short tandem repeats in coding and noncoding regions of the genome that vary in length between strains and offer reproducible genotype calling for individual strains (typeability) and high resolution to distinguish between strains (discriminatory power) (33). This type of marker has been used extensively and has proven to be robust in humans and in pathogens such as Plasmodium falciparum for "molecular fingerprinting" and for studying the evolution of drug resistance (34)(35)(36). Here, we describe our multilocus microsatellite genotyping method and use it to investigate the global population structure of P. jirovecii, to study the evolution of sulfa antibiotic resistance, and to evaluate typeability and discriminatory power within one cohort.…”

Independent Lineages of Highly Sulfadoxine-ResistantPlasmodium falciparumHaplotypes, Eastern Africa

“…These parasites were genotyped at dhps loci by using amplification and Sanger sequencing ( 18 , 20 ), and only those with pure A581 G genotypes were genotyped at microsatellites. For parasites from Tanzania, the mutant alleles A437 G and K540 E are nearly fixed; A581 G was identified by pyrosequencing ( 12 ).…”

“…Five microsatellite loci flanking the dhps gene were genotyped in all isolates: −2.9 and −0.13 kB upstream, and 0.03, 0.5, and 9 kB downstream of dhps ( 20 ). PCR products of amplifications of individual loci were sized on a 310 Genetic Analyzer (Applied Biosystems, Foster City, CA, USA), and allele lengths were scored by using GeneMapper v4.1 (Applied Biosystems).…”

Genetic Evidence of Drug-Resistant Malarial Strain from the Democratic Republic of the Congo Imported to Guatemala

“…The parent study and ancillary studies have been described in detail ( 13 – 16 ). For the analysis reported here, we selected 7 clusters, all of which included >10 P. falciparum –positive persons, as part of a study to quantify gene flow in P. falciparum strains within the DRC.…”