Acta Parasitologica

, Volume 61, Issue 4, pp 828–835 | Cite as

Development of a rapid and reliable assay for in vitro determination of compound cidality against the asexual stages of Plasmodium falciparum

  • Pavithra ViswanathEmail author
  • Sapna Morayya
  • Nikhil Rautela
  • Achyut Sinha


The pace of anti-malarial drug discovery is often impeded due to the lack of tools to determine the cidality of compounds in vitro. An anti-malarial compound must have a cidal mode of action, i.e. kill parasites, in order to quickly reduce parasite load. A static compound that merely inhibits growth must be identified early on in the discovery cascade. In this paper, we describe a high-throughput fluorescent assay for determination of the cidality of an anti-malarial compound. The assay works on the principle that cultures treated with a static compound will exhibit re-growth while treatment with a cidal compound leads to a marked reduction in parasite number. Parasite cultures are treated with the drug for 48 or 72 h following which the drug is washed off. Cultures are allowed to recover in drug-free media for 72 h and DNA content estimated using the fluorescent dye SyBR Green I. Following estimation of IC50 and IC99 values, we find that the IC99/IC50 ratio is a reliable indicator of the cidality of a compound. Cidal compounds like artemisinin and chloroquine display an IC99/IC50 ratio <5 while the ratio for a static compound like atovaquone is >5. This correlation holds true for various anti-malarial drugs with known modes of action. Importantly, the IC99/IC50 ratio drops to <5 when a compound becomes cidal in action with longer duration of treatment. The assay is robust, reliable and provides a fast and effective means for prioritizing cidal compounds for progression along the drug discovery cascade.


Anti-malarial cidality mode of action malaria drug discovery SyBR Green I 


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Copyright information

© Witold Stefański Institute of Parasitology, Polish Academy of Sciences 2016

Authors and Affiliations

  • Pavithra Viswanath
    • 1
    Email author
  • Sapna Morayya
    • 1
  • Nikhil Rautela
    • 1
  • Achyut Sinha
    • 1
  1. 1.Department of Radiology and Biomedical ImagingUniversity of California San FranciscoSan FranciscoUSA

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