title: Assessment of the Worldwide Antimalarial Resistance Network Standardized Procedure for In Vitro Malaria Drug Sensitivity Testing Using SYBR Green Assay for Field Samples with Various Initial Parasitemia Levels.
abstract: The malaria SYBR green assay, which is used to profilein vitrodrug susceptibility ofPlasmodium falciparum, is a reliable drug screening and surveillance tool. Malaria field surveillance efforts provide isolates with various low levels of parasitemia. To be advantageous, malaria drug sensitivity assays should perform reproducibly among various starting parasitemia levels rather than at one fixed initial value. We examined the SYBR green assay standardized procedure developed by the Worldwide Antimalarial Resistance Network (WWARN) for its sensitivity and ability to accurately determine the drug concentration that inhibits parasite growth by 50% (IC50) in samples with a range of initial parasitemia levels. The initial sensitivity determination of the WWARN procedure yielded a detection limit of 0.019% parasitemia.P. falciparumlaboratory strains and field isolates with various levels of initial parasitemia were then subjected to a range of doses of common antimalarials. The IC50s were comparable for laboratory strains with between 0.0375% and 0.6% parasitemia and for field isolates with between 0.075% and 0.6% parasitemia for all drugs tested. Furthermore, assay quality (Z') analysis indicated that the WWARN procedure displays high robustness, allowing for drug testing of malaria field samples within the derived range of initial parasitemia. The use of the WWARN procedure should allow for the inclusion of more malaria field samples in malaria drug sensitivity screens that would have otherwise been excluded due to low initial parasitemia levels.
authors: Department of Emerging Infectious Diseases-Global Emerging Infections Surveillance and Response System (DEID-GEIS) Program, U.S. Army Medical Research Directorate-Kenya (USAMRD-K), Kenya Medical Research Institute (KEMRI)-Walter Reed Project, Kisumu, Kenya.
authors: Agnes C
authors: AC
authors: Cheruiyot
authors: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors: Jennifer M
authors: JM
authors: Auschwitz
authors: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors: Patricia J
authors: PJ
authors: Lee
authors: Department of Emerging Infectious Diseases-Global Emerging Infections Surveillance and Response System (DEID-GEIS) Program, U.S. Army Medical Research Directorate-Kenya (USAMRD-K), Kenya Medical Research Institute (KEMRI)-Walter Reed Project, Kisumu, Kenya.
authors: Redemptah A
authors: RA
authors: Yeda
authors: Department of Emerging Infectious Diseases-Global Emerging Infections Surveillance and Response System (DEID-GEIS) Program, U.S. Army Medical Research Directorate-Kenya (USAMRD-K), Kenya Medical Research Institute (KEMRI)-Walter Reed Project, Kisumu, Kenya.
authors: Charles O
authors: CO
authors: Okello
authors: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors: Susan E
authors: SE
authors: Leed
authors: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors: Mayank
authors: M
authors: Talwar
authors: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors: Tushar
authors: T
authors: Murthy
authors: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors: Heather W
authors: HW
authors: Gaona
authors: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
authors: Mark R
authors: MR
authors: Hickman
authors: Department of Emerging Infectious Diseases-Global Emerging Infections Surveillance and Response System (DEID-GEIS) Program, U.S. Army Medical Research Directorate-Kenya (USAMRD-K), Kenya Medical Research Institute (KEMRI)-Walter Reed Project, Kisumu, Kenya.
authors: Hoseah M
authors: HM
authors: Akala
authors: Department of Emerging Infectious Diseases-Global Emerging Infections Surveillance and Response System (DEID-GEIS) Program, U.S. Army Medical Research Directorate-Kenya (USAMRD-K), Kenya Medical Research Institute (KEMRI)-Walter Reed Project, Kisumu, Kenya.
authors: Edwin
authors: E
authors: Kamau
authors: Department of Emerging Infectious Diseases-Global Emerging Infections Surveillance and Response System (DEID-GEIS) Program, U.S. Army Medical Research Directorate-Kenya (USAMRD-K), Kenya Medical Research Institute (KEMRI)-Walter Reed Project, Kisumu, Kenya jacob.d.johnson.mil@mail.mil.
authors: Jacob D
authors: JD
authors: Johnson
mesh_terms: D000962:Antimalarials / Q000494:pharmacology; D037621:Artemisinins / Q000494:pharmacology; D053626:Atovaquone / Q000494:pharmacology; D052160:Benzothiazoles; D001681:Biological Assay / Q000592:standards*; D002738:Chloroquine / Q000494:pharmacology; D016054:DNA, Protozoan / Q000032:analysis; D003959:Diamines; D004351:Drug Resistance / Q000235:genetics; D004912:Erythrocytes / Q000187:drug effects / Q000469:parasitology; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D020128:Inhibitory Concentration 50; D016778:Malaria, Falciparum / Q000175:diagnosis* / Q000188:drug therapy / Q000469:parasitology; D015767:Mefloquine / Q000494:pharmacology; D009930:Organic Chemicals / Q000737:chemistry*; D018512:Parasitemia / Q000175:diagnosis* / Q000188:drug therapy; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D062486:Public Health Surveillance; D011804:Quinolines; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D052160:Benzothiazoles; D016054:DNA, Protozoan; D003959:Diamines; D005456:Fluorescent Dyes; D009930:Organic Chemicals; D011804:Quinolines; C098022:SYBR Green I; D002738:Chloroquine; C031327:artemisinin; D015767:Mefloquine; D053626:Atovaquone