Molecular Detection of Mutations in the Propeller Domain of Kelch 13 and pfmdr1 Copy Number Variation in Plasmodium falciparum Isolates from Thailand Collected from 2002 to 2007

We determined the prevalence of Kelch 13 mutations and pfmdr1 copy number in samples collected from the Thailand–Myanmar border, the Thailand–Cambodia border, and southern Thailand from 2002 to 2007. C580Y was the most prevalent in Trat (Thailand–Cambodia border) and Ranong (Thailand–Myanmar border) at 42% (24/57) and 13% (6/48), respectively. Less predominant mutations were also identified including R539T (7%, 4/57) and Y493H (2%, 1/57) in Trat, P574L (6%, 3/48) and P553L (2%, 1/48) in Ranong, and N537I and D452E (7%, 1/15) in Sangkhlaburi (Thailand–Myanmar border). Samples from Mae sot (33%, 11/33) harbored the highest percentage of multiple pfmdr1 copies, followed by Trat (18%, 10/57), Chiang Dao in 2003 (13%, 4/30), Phang Nga (5%, 2/44), and Chiang Dao in 2002 (4%, 1/26). This retrospective study provides geographic diversity of K13 and pfmdr1 copies and the emergence of these molecular markers in Thailand, an important background information for future surveillance in the region.

Distribution and temporal dynamics of P. falciparum chloroquine resistance transporter mutations associated with piperaquine resistance in Northern Cambodia

Background Newly emerged mutations within the Plasmodium falciparum chloroquine resistance transporter (PfCRT) can confer piperaquine resistance in the absence of amplified plasmepsin II (pfpm2). In this study, we estimated the prevalence of co-circulating piperaquine resistance mutations in P. falciparum isolates collected in northern Cambodia from 2009-2017. Methods The sequence of pfcrt was determined for 410 P. falciparum isolates using PacBio amplicon sequencing or whole genome sequencing. Quantitative PCR was used to estimate pfpm2 and pfmdr1 copy number. Results Newly emerged PfCRT mutations increased in prevalence after the change to dihydroartemisinin-piperaquine in 2010, with >98% of parasites harboring these mutations by 2017. After 2014, the prevalence of PfCRT F145I declined, being out-competed by parasites with less resistant, but more fit PfCRT alleles. After the change to artesunate-mefloquine, the prevalence of parasites with amplified pfpm2 decreased, with nearly half of piperaquine-resistant PfCRT mutants having single copy pfpm2. Conclusions The large proportion of PfCRT mutants that lack pfpm2 amplification emphasizes the importance of including PfCRT mutations as part of molecular surveillance for piperaquine resistance in this region. Likewise, it is critical to monitor for amplified pfmdr1 in these PfCRT mutants, as increased mefloquine pressure could lead to mutants resistant to both drugs.

Counter-Selection of Antimalarial Resistance Polymorphisms by Intermittent Preventive Treatment in Pregnancy

Background Innovative approaches are needed to limit antimalarial resistance evolution. Understanding the role of intermittent preventive treatment in pregnancy (IPTp) on the selection for resistance and the impact such selection has on pregnancy outcomes can guide future interventions. Methods Plasmodium falciparum isolates (n = 914) from 2 randomized clinical trials were screened for pfmdr1 copy number variation and pfcrt, pfmdr1, pfdhfr, and pfdhps resistance markers. The trials were conducted between 2010 and 2013 in Benin, Gabon, Kenya, and Mozambique to establish the efficacy of IPTp-mefloquine (MQ) compared with IPTp-sulphadoxine-pyrimethamine (SP) in human immunodeficiency virus (HIV)-uninfected and to IPTp-placebo in HIV-infected women. Results In HIV-uninfected women, the prevalence of pfcrt mutants, pfdhfr/pfdhps quintuple mutants, and pfmdr1 copy number was similar between women receiving IPT-SP and IPTp-MQ. However, prevalence of pfmdr1 polymorphism 86Y was lower in the IPTp-MQ group than in the IPTp-SP group, and within the IPTp-MQ group it was lower at delivery compared with recruitment. No effect of IPTp-MQ on resistance markers was observed among HIV-infected women. The carriage of resistance markers was not associated with pregnancy outcomes. Conclusions Selection of wild-type pfmdr1 polymorphism N86 by IPTp-MQ highlights the strong selective pressure IPTp can exert and the opportunity for using negative cross-resistance in drug choice for clinical treatment and IPTp.

Plasmodium falciparum Isolates with Increased pfmdr1 Copy Number Circulate in West Africa

ABSTRACT Amplification of pfmdr1 in Plasmodium falciparum is linked to resistance to aryl-amino-alcohols and in reduced susceptibility to artemisinins. We demonstrate here that duplicated pfmdr1 genotypes circulate in West Africa. The monitoring of this prevalence in Africa appears essential for determining the antimalarial policy and to maintain the efficiency of artemisinin-based combination therapy (ACT) for as long as possible.