Ex vivo susceptibility of Plasmodium falciparum to antimalarial drugs in western, northern, and eastern Cambodia, 2011-2012: association with molecular markers.
In 2008, dihydroartemisinin (DHA)-piperaquine (PPQ) became the first-line treatment for uncomplicated Plasmodium falciparum malaria in western Cambodia. Recent reports of increased treatment failure rates after DHA-PPQ therapy in this region suggest that parasite resistance to DHA, PPQ, or both is now adversely affecting treatment. While artemisinin (ART) resistance is established in western Cambodia, there is no evidence of PPQ resistance. To monitor for resistance to PPQ and other antimalarials, we measured drug susceptibilities for parasites collected in 2011 and 2012 from Pursat, Preah Vihear, and Ratanakiri, in western, northern, and eastern Cambodia, respectively. Using a SYBR green I fluorescence assay, we calculated the ex vivo 50% inhibitory concentrations (IC50s) of 310 parasites to six antimalarials: chloroquine (CQ), mefloquine (MQ), quinine (QN), PPQ, artesunate (ATS), and DHA. Geometric mean IC50s (GMIC50s) for all drugs (except PPQ) were significantly higher in Pursat and Preah Vihear than in Ratanakiri (P ≤ 0.001). An increased copy number of P. falciparum mdr1 (pfmdr1), an MQ resistance marker, was more prevalent in Pursat and Preah Vihear than in Ratanakiri and was associated with higher GMIC50s for MQ, QN, ATS, and DHA. An increased copy number of a chromosome 5 region (X5r), a candidate PPQ resistance marker, was detected in Pursat but was not associated with reduced susceptibility to PPQ. The ex vivo IC50 and pfmdr1 copy number are important tools in the surveillance of multidrug-resistant (MDR) parasites in Cambodia. While MDR P. falciparum is prevalent in western and northern Cambodia, there is no evidence for PPQ resistance, suggesting that DHA-PPQ treatment failures result mainly from ART resistance.
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
Pharath
P
Lim
Dalin
D
Dek
Vorleak
V
Try
Richard T
RT
Eastman
Sophy
S
Chy
Sokunthea
S
Sreng
Seila
S
Suon
Sivanna
S
Mao
Chantha
C
Sopha
Baramey
B
Sam
Elizabeth A
EA
Ashley
Olivo
O
Miotto
Arjen M
AM
Dondorp
Nicholas J
NJ
White
Xin-zhuan
XZ
Su
Meng Chuor
MC
Char
Jennifer M
JM
Anderson
Chanaki
C
Amaratunga
Didier
D
Menard
Rick M
RM
Fairhurst
D000962:Antimalarials / Q000627:therapeutic use*; D037621:Artemisinins / Q000627:therapeutic use*; D052160:Benzothiazoles; D015415:Biomarkers / Q000378:metabolism; D002160:Cambodia / Q000453:epidemiology; D056915:DNA Copy Number Variations; D003959:Diamines; D004338:Drug Combinations; D018432:Drug Resistance, Multiple / Q000235:genetics*; D062665:Epidemiological Monitoring; D015870:Gene Expression; D006801:Humans; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000453:epidemiology / Q000469:parasitology; D008856:Microscopy, Fluorescence; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics* / Q000378:metabolism; D009930:Organic Chemicals; D021261:Parasitic Sensitivity Tests; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011804:Quinolines / Q000627:therapeutic use*; D010879:Piperazines
D000962:Antimalarials; D037621:Artemisinins; D052160:Benzothiazoles; D015415:Biomarkers; D003959:Diamines; D004338:Drug Combinations; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009930:Organic Chemicals; D011804:Quinolines; C513498:Mdr1 protein, Plasmodium falciparum; C098022:SYBR Green I; C039060:artenimol; C034759:piperaquine; D010879:Piperazines