Pyrimethamine and Proguanil Resistance-Conferring Mutations in Plasmodium falciparum Dihydrofolate Reductase: Polymerase Chain Reaction Methods for Surveillance in Africa

Plowe, Christopher V.; Djimdé, Abdoulaye; Bouaré, Madama; Doumbo, Ogobara K.; Wellems, Thomas E.

doi:10.4269/ajtmh.1995.52.565

Cited by 612 publications

(545 citation statements)

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“…First, dhfr resistance alleles containing the I164L mutation conferring high levels of pyrimethamine resistance (Plowe et al 1995) are common in Thailand but absent in the populations studied from Laos . Hence, dhfr alleles from Thailand will have higher fitness than those from Laos in the presence of drug selection and will therefore spread more rapidly, giving rise to more extensive hitchhiking.…”

Section: Discussionmentioning

confidence: 99%

Selection strength and hitchhiking around two anti-malarial resistance genes

et al. 2005

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Neutral mutations may hitchhike to high frequency when they are situated close to sites under positive selection, generating local reductions in genetic diversity. This process is thought to be an important determinant of levels of genomic variation in natural populations. The size of genome regions affected by genetic hitchhiking is expected to be dependent on the strength of selection, but there is little empirical data supporting this prediction. Here, we compare microsatellite variation around two drug resistance genes (chloroquine resistance transporter ( pfcrt), chromosome 7, and dihydrofolate reductase (dhfr), chromosome 4) in malaria parasite populations exposed to strong (Thailand) or weak selection (Laos) by anti-malarial drugs. In each population, we examined the point mutations underlying resistance and length variation at 22 (chromosome 4) or 25 (chromosome 7) microsatellite markers across these chromosomes. All parasites from Thailand carried the K76T mutation in pfcrt conferring resistance to chloroquine (CQ) and 2-4 mutations in dhfr conferring resistance to pyrimethamine. By contrast, we found both wild-type and resistant alleles at both genes in Laos. There were dramatic differences in the extent of hitchhiking in the two countries. The size of genome regions affected was smaller in Laos than in Thailand. We observed significant reduction in variation relative to sensitive parasites for 34-64 kb (2-4 cM) in Laos on chromosome 4, compared with 98-137 kb (6-8 cM) in Thailand. Similarly, on chromosome 7, we observed reduced variation for 34-69 kb (2-4 cM) around pfcrt in Laos, but for 195-268 kb (11-16 cM) in Thailand. Reduction in genetic variation was also less extreme in Laos than in Thailand. Most loci were monomorphic in a 12 kb region surrounding both genes on resistant chromosomes from Thailand, whereas in Laos, even loci immediately proximal to selective sites showed some variation on resistant chromosomes. Finally, linkage disequilibrium (LD) decayed more rapidly around resistant pfcrt and dhfr alleles from Laos than from Thailand. These results demonstrate that different realizations of the same selective sweeps may vary considerably in size and shape, in a manner broadly consistent with selection history. From a practical perspective, genomic regions containing resistance genes may be most effectively located by genome-wide association in populations exposed to strong drug selection. However, the lower levels of LD surrounding resistance alleles in populations under weak selection may simplify identification of functional mutations.

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Section: Discussionmentioning

confidence: 99%

Selection strength and hitchhiking around two anti-malarial resistance genes

et al. 2005

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“…DNA was extracted from filter papers by the Chelex-100 DNA extraction method. 12 Plasmodium falciparum DNA was detected using a species-specific nested PCR as previously described. 13 As controls, DNA from the P. falciparum laboratory isolates 3D7, Dd2, HB3, and FCR3 was investigated in parallel.…”

Section: Methodsmentioning

confidence: 99%

Association of Plasmodium Falciparum Isolates Encoding the P. Falciparum Chloroquine Resistance Transporter Gene K76t Polymorphism With Anemia and Splenomegaly, but Not With Multiple Infections

Abdel-Aziz

Oster²,

Stich³

et al. 2005

The American Journal of Tropical Medicine and Hygiene

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Abstract. The aim of the study was to assess whether infections with Plasmodium falciparum isolates encoding the P. falciparum chloroquine resistance transporter (pfcrt) gene K76T polymorphism, a molecular marker for chloroquine resistance, are associated with multiple infections, age, or clinical signs of malaria in a semi-immune population in a holoendemic area of Burkina Faso. The parameters of interest were investigated in 210 P. falciparum-positive inhabitants. Logistic regression analysis showed that pfcrt K76T-carrying isolates are significantly more likely to cause anemia and splenomegaly. Furthermore, we found that infections with P. falciparum isolates encoding pfcrt K76T are dependent on age rather than multiple infections. Our findings suggest that pfcrt K76T might serve as a valuable marker for assessing the long-term clinical effect of chronic infections with chloroquine-resistant P. falciparum isolates in populations, without the need of drug efficacy trials.

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“…DNA was prepared by Chelex extraction, as previously described (Plowe et al 1995). A fluorescent PCR analysed block 2 of the msp-1 and of msp-2 domains, as described (Jafari et al 2004).…”

Section: Dna Preparation and Pcr Amplificationmentioning

confidence: 99%

Dramatically decreased therapeutic efficacy of chloroquine and sulfadoxine‐pyrimethamine, but not mefloquine, in southern Benin

Aubouy¹,

Fiévet²,

Bertin³

et al. 2007

Tropical Med Int Health

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Summaryobjective To evaluate the in vivo therapeutic efficacy of chloroquine (CQ), sulfadoxinepyrimethamine (SP) and mefloquine (MQ) in children presenting with uncomplicated malaria in Benin.methods Drug efficacy was tested according to the WHO in vivo 28-day protocol. For failures that occurred after 7 days of follow-up, paired pre-and post-treatment blood samples were genotyped at msp1 and msp2 loci to distinguish new infections and recrudescent strains. Children enrolled were randomly assigned to a therapeutic group (CQ, n ¼ 14; SP, n ¼ 42; MQ, n ¼ 44). The number of CQ treatment was intentionally restricted after 1 month, as its use was considered to constitute a danger for children.results Chloroquine and SP showed very high failure rates (85.7% and 50%, respectively), whereas MQ treatment was successful in 97.5%. The molecular tool allowed to re-evaluate two new infections previously considered as failures.conclusions Chloroquine should no longer be used to treat children presenting with Plasmodium falciparum malaria in Benin.

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Pyrimethamine and Proguanil Resistance-Conferring Mutations in Plasmodium falciparum Dihydrofolate Reductase: Polymerase Chain Reaction Methods for Surveillance in Africa

Cited by 612 publications

References 0 publications

Selection strength and hitchhiking around two anti-malarial resistance genes

Selection strength and hitchhiking around two anti-malarial resistance genes

Association of Plasmodium Falciparum Isolates Encoding the P. Falciparum Chloroquine Resistance Transporter Gene K76t Polymorphism With Anemia and Splenomegaly, but Not With Multiple Infections

Dramatically decreased therapeutic efficacy of chloroquine and sulfadoxine‐pyrimethamine, but not mefloquine, in southern Benin

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