ABSTRACT
Plasmodium falciparum(Lab.culture FCR3 isolate) developed resistance to sodium artesunate after exposure to the drug in vitro.The drug effective concentration which resulted in 50 per cent schizont maturation inhibition (IC50) was 1.6ng/ml (4.1nmol/L) before exposure to the drug.After 130 days of discontiguous exposure to sodium artesunate in a stepwise fashion,the sensitivity of the isolate to the drug decreased,with its IC50 3-fold higher than that of the parent isolate.The resistance to artesunate decreased significantly after the resistant line was grown in drug-free medium.
ABSTRACT
Objective To identify the genotype of merozoite surface protein 1 (MSP1) of Plasmodium falciparum isolates from Hainan Province. Methods Nested PCR was applied to amplify the MSP1 of Blocks 2 and 3 Plasmodium falciparum isolates from Hainan Province. Two allelic family representitive gene fragments were sequenced.Results From 36 out of 39 blood samples from Plasmodium falciparum patients, 44 gene fragments of blocks 2 and 3 of the MSP1 were amplified, of which the MAD20 type allele was dominant(75%). followed by K1 type allele. No RO33 type allele was found. The mixed infection rate of the two different allelic type was 19 4%. Sequence analysis showed that the sequences of MAD20 and K1 type isolates from Hainan Province were highly homologous to that of the MAD20 and K1 allelic prototypes.Conclusion Two principal allelic types of MSP1 gene, MAD20 and K1 type, exist in malaria endemic areas in Hainan Province, the MAD20 type being the dominant.