The polymorphism analyses of K13, pfmdr1, pfcrt
, and pfdhps genes were successful for 98.3% to 100% isolates.
Table 1--Sequence analysis of portions of Pvdhfr, Pvdhps, Pfdhfr, Pfdhps, Pfcrt
, Pfmdrl and dhfr genes of P.
Nested PCR followed by restriction endonuclease digestion was used to detect pfcrt
Studies carried out in South Eastern Cameroon  as well as in Kenya and Malawi suggested that removal of chloroquine pressure from the population led to gradual reduction in the proportion of circulating mutant genotypes of Pfcrt
gene and a return to the chloroquine sensitive genotype [21-23].
Full-length analysis of pfcrt
was conducted in this study to provide a thorough overview on the pattern of mutations of pfcrt
and the prevalence of P falciparum towards CQR in Sabah, Malaysia.
Mutations conferring drug resistance in malaria parasite drug transporters Pgh1 and PfCRT
do not affect steady-state vacuolar [Ca.sup.2+].
Now, the Australian team has proved that PfCRT
"provides an exit route for chloroquine," which does not reach the concentration required to kill the parasite.
gene is located on chromosome 7 and codes for Pfcrt
, a vacuolar membrane transporter protein.
Markers that showed the underlying genetic background predisposing to the K13 mutant were also reported, includingpfarpslO, pffd, pfmdr2, and pfcrt
. Specific single nucleotide polymorphisms of these genes, such as V127M of pfarpslO, D193Y of pffd, and T484I of pfmdr2, were found at a similar prevalence as K13 mutations (9).
Ingasiaetal., "The Role ofPfmdrl and Pfcrt
in changing Chloroquine, Amodiaquine, Mefloquine and Lumefantrine susceptibility in Western-Kenya P.
(K76T) point mutation favours clone multiplicity and disease severity in Plasmodium falciparum infection.
In their study Kublin and colleagues (147) measured the prevalence of the pfcrt
76T genotype (a molecular marker for CHQ-resistance) and observed that after 10 yr of CHQ withdrawal, the prevalence of this genotype decreased from a peak of 85 per cent in 1992 to only 13 per cent in 2000.