Analysis of anti-malarial resistance markers in pfmdr1 and pfcrt across Southeast Asia in the Tracking Resistance to Artemisinin Collaboration.
BACKGROUND
Declining anti-malarial efficacy of artemisinin-based combination therapy, and reduced Plasmodium falciparum susceptibility to individual anti-malarials are being documented across an expanding area of Southeast Asia (SEA). Genotypic markers complement phenotypic studies in assessing the efficacy of individual anti-malarials.


METHODS
The markers pfmdr1 and pfcrt were genotyped in parasite samples obtained in 2011-2014 at 14 TRAC (Tracking Resistance to Artemisinin Collaboration) sites in mainland Southeast Asia using a combination of PCR and next-generation sequencing methods.


RESULTS
Pfmdr1 amplification, a marker of mefloquine and lumefantrine resistance, was highly prevalent at Mae Sot on the Thailand-Myanmar border (59.8% of isolates) and common (more than 10%) at sites in central Myanmar, eastern Thailand and western Cambodia; however, its prevalence was lower than previously documented in Pailin, western Cambodia. The pfmdr1 Y184F mutation was common, particularly in and around Cambodia, and the F1226Y mutation was found in about half of samples in Mae Sot. The functional significance of these two mutations remains unclear. Other previously documented pfmdr1 mutations were absent or very rare in the region. The pfcrt mutation K76T associated with chloroquine resistance was found in 98.2% of isolates. The CVIET haplotype made up 95% or more of isolates in western SEA while the CVIDT haplotype was common (30-40% of isolates) in north and northeastern Cambodia, southern Laos, and southern Vietnam.


CONCLUSIONS
These findings generate cause for concern regarding the mid-term efficacy of artemether-lumefantrine in Myanmar, while the absence of resistance-conferring pfmdr1 mutations and SVMNT pfcrt haplotypes suggests that amodiaquine could be an efficacious component of anti-malarial regimens in SEA.
Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Krongkan
K
Srimuang
Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand.|Wellcome Trust Sanger Institute, Hinxton, UK.|Medical Research Council (MRC) Centre for Genomics and Global Health, University of Oxford, Oxford, UK.
Olivo
O
Miotto
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, 20852, USA.
Pharath
P
Lim
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, 20852, USA.
Rick M
RM
Fairhurst
Wellcome Trust Sanger Institute, Hinxton, UK.|Medical Research Council (MRC) Centre for Genomics and Global Health, University of Oxford, Oxford, UK.
Dominic P
DP
Kwiatkowski
Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand.|Centre for Tropical Medicine & Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Charles J
CJ
Woodrow
Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. noi@tropmedres.ac.|Mahidol Oxford Tropical Medicine Research Unit, Bangkok, Thailand. noi@tropmedres.ac.
Mallika
M
Imwong
D000655:Amodiaquine / Q000494:pharmacology; D000962:Antimalarials / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology*; D001210:Asia, Southeastern; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004351:Drug Resistance; D004983:Ethanolamines / Q000494:pharmacology; D005449:Fluorenes / Q000494:pharmacology; D005787:Gene Frequency; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D000078102:Lumefantrine; D026901:Membrane Transport Proteins / Q000235:genetics*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics*; D020125:Mutation, Missense; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins / Q000235:genetics*
D000655:Amodiaquine; D000962:Antimalarials; D037621:Artemisinins; D016054:DNA, Protozoan; D004983:Ethanolamines; D005449:Fluorenes; D000078102:Lumefantrine; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D015800:Protozoan Proteins; C513498:Mdr1 protein, Plasmodium falciparum; C416369:PfCRT protein, Plasmodium falciparum; C031327:artemisinin
Amodiaquine; Anti-malarial resistance; Artemisinin; Chloroquine; Combination therapy; Malaria; Mefloquine; Plasmodium falciparum; pfcrt; pfmdr1