Antimalarial drug resistance has been a hindrance to achieving a malaria free worldrnsince the first case of chloroquine resistance was recorded in South Eastern Asia SEA in 1950s.rnConsequently evaluating the efficacy of the scarce frontline antimalarials against the Kenyan P.rnfalciparum field isolates is a top priority for efficient monitoring of drug failure and guiding treatmentrnpolicy in the country
A total of 255 clinical P. falciparum isolates collected from patients presenting withrnuncomplicated malaria at six hospital sites in Kenya between 2008 and 2021 were tested for immediaternex-vivo and in-vitro susceptibility to selected antimalarials using SYBR Green I fluorescence-basedrnassay. Drugs tested include piperaquine PPQ dihydroartemisinin DHA lumefantrine LMrnartemether ART and chloroquine CQ. W2 and d6 reference clones were tested in parallel as thernassay and test controls.
Lumefantrine median IC50s inclined significantly between 2008 11.0 nM n54 IQR 2.7rnnM to 26.9 nM and 2021 30.55 nM n51 IQR 3.2 nM to 47.7 nM p0.05. A steady statisticallyrnsignificant decline in median IC50 for CQ was observed between 2008 7.9 nM n36 IQR 3.9 nM torn15.8 nM and 2021 4.6 nM n62 IQR 3.1 nM to 8.2 nM p0.05. However the PPQ susceptibilityrnduring the study timeline was stable median IC50 of 16.8 nM n34 IQR 10.8 nM to 23.1 nM in 2008rnand 14.1 nM n42 IQR 6.4 nM to 21.3 nM in 2021.
: There were varying trends in response of naturally acquired infection clinical isolates between 2008 and 2021 as depicted by increasing sensitivity to CQ and impaired response to LM. These findings underscore the paucity of the drug resistance profile trends and warrant continued surveillance in order to support effective treatment.