Comparison between Flow Cytometry, Microscopy, and Lactate Dehydrogenase-Based Enzyme-Linked Immunosorbent Assay for Plasmodium falciparum Drug Susceptibility Testing under Field Conditions.
Flow cytometry is an objective method for conducting in vitro antimalarial sensitivity assays with increasing potential for application in field sites. We examined in vitro susceptibility to seven anti-malarial drugs for 40 fresh P. falciparum field isolates via a flow cytometry method (FCM), a colorimetric LDH-based ELISA : DELI), and standard microscopic slide analysis of growth. For FCM, 184/280 (66%) assays met analytical acceptance criteria, compared to 166/280 (59%) for DELI. There was good agreement between FCM and microscopy, while DELI tended to produce higher half-maximal inhibition constants (IC50s) than FCM, with an overall bias of 2.2-fold (Bland-Altman comparison). Values for artesunate and dihydroartemisinin were most affected. Paradoxical increases in signal at very high concentrations of mefloquine and related compounds were more marked with the DELI assay, suggesting that off-target effects on LDH production may be responsible. Loss of FCM signal due to reinvasion or slow growth was observed in a small number of samples. These results extend previous work on use of flow cytometry to determine antimalarial susceptibility in terms of the number of samples, range of drugs, and comparison with other methods.
Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Charles J
CJ
Woodrow
Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Tak, Thailand.
Chirapat
C
Wangsing
Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Tak, Thailand.
Kanlaya
K
Sriprawat
Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Tak, Thailand.
Peter R
PR
Christensen
Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Tak, Thailand.
Francois
F
Nosten
Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore.
Laurent
L
Rénia
Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore.
Bruce
B
Russell
Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Biopolis, Singapore Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore benoit_malleret@immunol.a-star.edu.sg.
Benoît
B
Malleret
D000962:Antimalarials / Q000494:pharmacology*; D003124:Colorimetry / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D020128:Inhibitory Concentration 50; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008853:Microscopy / Q000379:methods*; D021261:Parasitic Sensitivity Tests / Q000379:methods*; D010963:Plasmodium falciparum / Q000187:drug effects*
D000962:Antimalarials; D007770:L-Lactate Dehydrogenase