In-vitro activity of artemether, lumefantrine, dihydroartemisinin and piperaquine against Plasmodium falciparum clinical isolates transported in a formulated transport medium

Abstract

Introduction: Development of resistance to antimalarials has emerged as one of the greatest challenges facing malaria control today. In vitro drug sensitivity relies on the growth of plasmodium in the presence of the antimalarials. Any delay beyond 24 hours in performing the assay results in decreased parasite viability and subsequent IC50 values. Fresh isolates brought in for assay from collection sites situated far from the laboratory require a medium to keep the parasites viable in order to produce results which more accurately reflect intrinsic antimalarial drug resistance. Objective: To evaluate the use of a formulated transport medium (TM) in maintaining the viability of plasmodium during storage at 40C against a panel of antimalarials, compared to the conventional EDTA anticoagulant. Methods: This was a cross-sectional study. Blood samples positive for Plasmodium falciparum by light microscopy were transported to the laboratory using TM and the conventional EDTA anticoagulant as control. Using 322 Plasmodium falciparum isolates from patients attending outpatient clinic at Chulaimbo sub county hospital, SYBR Green 1 in vitro assay IC50 was done against artemether, lumefantrine, dihydroartemisinin and piperaquine. Results: The mean IC50 values for drugs were not significantly different in either EDTA or TM samples. Similarly, there was no significant correlation between samples which were transported in EDTA except for the Artemisinin derivative DHA which had a significant correlation with ART (r = 0.123, p=0.03), LUM (r = 0.1382, p=0.01), and PPQ (r = 0.1281, p=0.02) and also in TM between DHA and LUM (r=0.1229, p=0.03). Conclusion: Similarity obtained in median IC50 between samples in EDTA anticoagulant and TM warrants its continued use. However, DHA significant correlation with most of the drugs used, calls for more research to expound on this finding.