title: Ex Vivo Drug Susceptibility Testing and Molecular Profiling of Clinical Plasmodium falciparum Isolates from Cambodia from 2008 to 2013 Suggest Emerging Piperaquine Resistance.
abstract: Cambodia's first-line artemisinin combination therapy, dihydroartemisinin-piperaquine (DHA-PPQ), is no longer sufficiently curative against multidrug-resistant Plasmodium falciparum malaria at some Thai-Cambodian border regions. We report recent (2008 to 2013) drug resistance trends in 753 isolates from northern, western, and southern Cambodia by surveying for ex vivo drug susceptibility and molecular drug resistance markers to guide the selection of an effective alternative to DHA-PPQ. Over the last 3 study years, PPQ susceptibility declined dramatically (geomean 50% inhibitory concentration [IC50] increased from 12.8 to 29.6 nM), while mefloquine (MQ) sensitivity doubled (67.1 to 26 nM) in northern Cambodia. These changes in drug susceptibility were significantly associated with a decreased prevalence of P. falciparum multidrug resistance 1 gene (Pfmdr1) multiple copy isolates and coincided with the timing of replacing artesunate-mefloquine (AS-MQ) with DHA-PPQ as the first-line therapy. Widespread chloroquine resistance was suggested by all isolates being of the P. falciparum chloroquine resistance transporter gene CVIET haplotype. Nearly all isolates collected from the most recent years had P. falciparum kelch13 mutations, indicative of artemisinin resistance. Ex vivo bioassay measurements of antimalarial activity in plasma indicated 20% of patients recently took antimalarials, and their plasma had activity (median of 49.8 nM DHA equivalents) suggestive of substantial in vivo drug pressure. Overall, our findings suggest DHA-PPQ failures are associated with emerging PPQ resistance in a background of artemisinin resistance. The observed connection between drug policy changes and significant reduction in PPQ susceptibility with mitigation of MQ resistance supports reintroduction of AS-MQ, in conjunction with monitoring of the P. falciparum mdr1 copy number, as a stop-gap measure in areas of DHA-PPQ failure.
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Suwanna
authors.initials: S
authors.lastname: Chaorattanakawee
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: David L
authors.initials: DL
authors.lastname: Saunders
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Darapiseth
authors.initials: D
authors.lastname: Sea
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Nitima
authors.initials: N
authors.lastname: Chanarat
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Kritsanai
authors.initials: K
authors.lastname: Yingyuen
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Siratchana
authors.initials: S
authors.lastname: Sundrakes
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Piyaporn
authors.initials: P
authors.lastname: Saingam
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Nillawan
authors.initials: N
authors.lastname: Buathong
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Sabaithip
authors.initials: S
authors.lastname: Sriwichai
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Soklyda
authors.initials: S
authors.lastname: Chann
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Youry
authors.initials: Y
authors.lastname: Se
authors.affiliation: National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia.
authors.forename: You
authors.initials: Y
authors.lastname: Yom
authors.affiliation: National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Thay Kheng
authors.initials: TK
authors.lastname: Heng
authors.affiliation: National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Nareth
authors.initials: N
authors.lastname: Kong
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Worachet
authors.initials: W
authors.lastname: Kuntawunginn
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Kuntida
authors.initials: K
authors.lastname: Tangthongchaiwiriya
authors.affiliation: Howard Hughes Medical Institute/Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Jacob
authors.affiliation: Howard Hughes Medical Institute/Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Shannon
authors.initials: S
authors.lastname: Takala-Harrison
authors.affiliation: Howard Hughes Medical Institute/Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Plowe
authors.affiliation: Division of Infectious Diseases, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA.
authors.forename: Jessica T
authors.initials: JT
authors.lastname: Lin
authors.affiliation: National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia.
authors.forename: Char Meng
authors.initials: CM
authors.lastname: Chuor
authors.affiliation: Royal Cambodian Armed Forces, Phnom Penh, Cambodia.
authors.forename: Satharath
authors.initials: S
authors.lastname: Prom
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Tyner
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Panita
authors.initials: P
authors.lastname: Gosi
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Paktiya
authors.initials: P
authors.lastname: Teja-Isavadharm
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand.
authors.forename: Chanthap
authors.initials: C
authors.lastname: Lon
authors.affiliation: Department of Immunology and Medicine, Armed Forces Research Institute of Medical Science, Bangkok, Thailand charlotte.a.lanteri.mil@mail.mil.
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Lanteri
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000962:Antimalarials / Q000627:therapeutic use*; D037621:Artemisinins / Q000627:therapeutic use; D002160:Cambodia; D002738:Chloroquine / Q000627:therapeutic use; D004351:Drug Resistance / Q000187:drug effects*; D005260:Female; D006801:Humans; D020128:Inhibitory Concentration 50; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000382:microbiology; D008297:Male; D015767:Mefloquine / Q000627:therapeutic use; D026901:Membrane Transport Proteins / Q000378:metabolism; D008875:Middle Aged; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D021261:Parasitic Sensitivity Tests / Q000379:methods; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D011804:Quinolines / Q000627:therapeutic use*; D055815:Young Adult; D010879:Piperazines
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D002738:Chloroquine; D015767:Mefloquine; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011804:Quinolines; C039060:artenimol; C031327:artemisinin; C034759:piperaquine; D010879:Piperazines