In Vitro Sensitivity Of Plasmodium Vivax To Chloroquine In China-myanmar Border

Objectives: To investigate chloroquine susceptibility of the Plasmodiumvivax isolates in China-Myanmar border and to analyze association betweendrug sensitivity and Pvmdr1gene polymorphism.Methods:(1) Short term culturing the single species infected Plasmodiumvivax isolates, which confirmed by microscopy and PCR, then using invitro microtest technique to calculate the IC50values for chloroquine drugsensitivity.(2) PCR amplify specific fragments of Pvmdr1, aftersequencing, gene mutation sites were determined by comparing withstandard strain of Salvador I (AY618622) Squence.Results:(1) The chloroquine IC50values of40Plasmodium vivax isolatesfrom the China-Myanmar border was2.116~713.2nM, Geometric mean,95%CI, Median were88.82nM,59.3~133nM and86.82nM respectively.IC50of eight Plasmodium vivax isolates were greater than220nM.(2) For25P. vivax isolates which chloroquine drug sensitivity and Pvmdr1geneamplification and sequencing were carried on successfully. It is been foundthat three isolates had Y976F mutation (mutation rate was12.00%), and thepresence of F1076L mutations in16isolates (mutation rate was%64.00),three isolates had both Y976F and F1076L mutation (mutation rate was12.00%).(3) There were6in8isolates which chloroquine IC50greaterthan220nM had successfully amplified and sequenced Pvmdr1gene, oneof them had Y976F mutation (mutation rate was16.67%), and four ofthem had F1076L mutation (mutation rate was66.67%), and one of themhad both Y976F and F1076L mutation (mutation rate was16.67%); Therewere19in32isolates which chloroquine IC50less than220nM hadsuccessfully amplified and sequenced Pvmdr1gene, one of them hadY976F mutation (mutation rate was10.53%), and12of them had F1076L mutation (mutation rate63.16%), and2isolates had both Y976F andF1076L mutation (mutation rate was10.53%); The Pvmdr1gene mutationrate for Y976F, F1076L or both were no significant differences (P>0.05) ingroups of chloroquine IC50great than220nM and less than220nM.Conclusions:(1) It is noticed that isolates from the China-Myanmar borderhad reduced susceptibility to CQ.(2) Isolates of Plasmodium vivax in theChina-Myanmar border carried Y976F, F1076L and Y976F, F1076L doublemutations.(3) No correlation was found between reduced chloroquinesensitivity and Pvmdr1mutations in this study.