Publication:

Susceptibility profile of the population to artemether, lumefantrine, dihydroartemisinin and piperaquine for samples transported in a formulated transport media and ethylenediamine tetraacetic acid anticoagulants: a study conducted in Maseno area, Western

Background In vitro sensitivity testing is one of the preferred methods of measuring susceptibility and undertaking surveillance of antimalarial drug efficacy. This method is able to measure Plasmodium falciparum susceptibility to several antimalarial drugs simultaneously, away from the influence of host immune related factors. The technique is being transitioned to ex vivo requiring tests on fresh sample. Such in vitro studies of field P. falciparum have been attributed to diminished viability as they transition from host ecosystem to lab conditions due to lack of a proper medium to stabilize the parasites. It is therefore imperative to calibrate the sample stabilization media to reduce artificial effects to the assay This study was meant to evaluate the effect of a formulated transport medium (TM) on viability of Plasmodium. The study assayed standard clones (W2 and 3D7), field isolates and compared the results with other published findings to come up with antimalarial susceptibility profile of the region.

Methods Blood samples were collected from 322 assenting individuals from Maseno division visiting Chulaimbo Sub county hospital and confirmed positive for malaria. Each sample, split in to EDTA versus TM was analysed for susceptibility to artemether (ART), lumefantrine (LUM), dihydroartemisinin (DHA) and piperaquine (PPQ) using malaria SYBR green assay. IC50 was determined for each sample between TM and EDTA using dose response curves.

Results Results showed that the IC50 values of the field isolates in EDTA were higher although not significant (p=0.99, 0.74, 0.68, 0.82 for ART, LUM, DHA and PPQ respectively) than those in the TM. Among the clones, PPQ was the only drug with a high significant IC50 decrease (p<0.001) in TM for the W2 and a moderately significant decrease (p=0.028) in EDTA for 3D7 clone.

Conclusions Lower IC50 values recorded by the field isolates against the antimalarials were indicative of their high susceptibility to the drugs.