Abstract:
Clinical resistance to artemisinin and its derivatives is now well established in
Southeast Asian (SEA). Studies from SEA have identified single nucleotide
polymorphisms (SNPs) which are significantly associated with delayed parasite
clearance rates. In this study we screened SNPs and established the SNP profile in
Kenyan isolates. DNA was extracted from 129 Plasmodium falciparum (P. falciparum)
positive patients collected in Kisumu from 2013-2014 and 1995-2010. 25 SNPs were
genotyped by Sequenome MassARRAY. P. falciparum multi-drug resistance gene 1
(pfmdr1) copy number variation was quantified using real time PCR. The in vitro
artemether susceptibility of the isolates was analyzed by malaria SYBR Green I assay.
Microsatellite analysis of MSP1/MSP2 was used to establish recrudescent verses new
infections in 20 follow up samples obtained from the efficacy study. Data showed that
pre-ACT samples contained 60% of the SNPs analyzed while the Post-Act samples had
24% of the SNPs. One Pre-ACT Sample (1.4%) contained multiple pfmdr1 copy
number and 7 of post ACT sample (9.9%) contained >1 pfmdr1 copy number. There
was a significant increase in Pfmdr1 copy number between pre-ACT and post-ACT
samples (P<0.001). The average clearance half-life was 2.6 hours. All parasites were
sensitive to artemisinin with significance difference in clearance half-life within subject
(p= 0.0001). There was no significant association between clearance half-life and
genotypes (p> 0.05). In vitro susceptibility to piperaquine reduced for isolates with
multiple pfmdr1 copy number to piperaquine and amodiaquine (P< 0.04). In conclusion
there is a possibility of selective sweep of SNP after elimination of previous drug
pressure and introduction of ACT. Pfmdr1 may putatively play a role in ACT
resistance.
