Prolonged incubation improves the micro-scale in-vitro test for drug sensitivity of Plasmodium falciparum

Mutations in the pfmdr1, dhfr and dhps genes of Plasmodium falciparum are associated with in-vivo drug resistance in West Papua, Indonesia

This study (conducted in 1996-99) examines the association of mutations in pfmdr1, dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes of Plasmodium falciparum with in-vivo drug resistance in West Papua, Indonesia. Initially, 85 patients infected with P. falciparum were treated with chloroquine, of whom 21 were cleared of parasites, 49 had parasitaemias classified as RI, RII or RIII resistance and 1 patient had recrudescent parasitaemia. Fansidar (pyrimethamine-sulfadoxine) was the second-line treatment and 18 patients were cleared of parasites and 31 had continuing infections classified as RI, RII or RIII resistance and 1 patient had recrudescent parasitaemia. The pfmdr1, dhfr and dhps genes were examined for mutations previously shown to be associated with resistance to these drugs. In this study, mutations in pfmdr1 were associated with chloroquine resistance and mutations in both dhfr and dhps were associated with Fansidar resistance in vivo. Interestingly, Gly-437 in dhps along with Arg-59/Asn-108 in dhfr were associated with RI, RII and RIII resistance whereas Glu-540 was highly associated with only RII and RIII Fansidar resistance. This finding supports the hypothesis that the molecular basis of RI, RII and RIII Fansidar resistance involves an accumulation of mutations in both dhfr and dhps. These results suggest that mutations in both dhfr and dhps genes are a good predictor of potential Fansidar treatment failure.

Pyrimethamine-sulfadoxine still effective against Plasmodium falciparum in Jayapura, Irian Jaya: RI-type resistance in 2 of 18 patients

The sensitivity of Plasmodium falciparum infections to pyrimethamine-sulfadoxine was studied in 18 Indonesian patients in Jayapura, Irian Jaya. In 16 of the 18 patients parasitaemia was cleared by day 6 and the patients remained without parasitaemia through day 28. Two of the 18 patients had late recrudescences consistent with RI-type resistance; one each on days 14 and 21. Pyrimethamine-sulfadoxine is still an effective antimalarial for most patients with falciparum malaria in Jayapura.

RII and RIII type resistance of Plasmodium falciparum to combination of mefloquine and sulfadoxine/pyrimethamine in Indonesia

2 of 36 Plasmodium falciparum infections were resistant (RII and RIII) in vivo to the combination of mefloquine (M) and sulfadoxine-pyrimethamine (SP) in Jayapura, Irian Jaya, Indonesia. Expected absorption of mefloquine and pyrimethamine was confirmed in the one resistant patient from whom sera were available, and the isolate from this patient was sensitive to mefloquine in vitro. Only 2 of 41 infections studied at the same time were resistant in vivo to SP. There was no clinical advantage of MSP compared with SP, and limited observations suggest there may be a disadvantage.

Chloroquine-resistant Plasmodium falciparum: now in Pakistani Punjab

To investigate the susceptibility of Plasmodium falciparum to chloroquine in Pakistani Punjab, in-vivo and in-vitro drug susceptibility was tested in 3 villages. Of 66 patients followed for up to 14 days after chloroquine treatment, 53 (80%) had parasites sensitive to chloroquine, 10 (15%) had parasites with early RI resistance, and 3 (5%) had parasites with RII resistance. Of 42 falciparum isolates investigated in vitro, 12 were sensitive, 8 intermediate, and 22 resistant to chloroquine. The degree of in-vivo resistance correlated with the degree of in-vitro resistance. It is concluded that chloroquine resistance is common among falciparum parasites in Pakistan and that this chloroquine resistance could explain the recent increase in the prevalence of falciparum malaria in the Punjab. Alternative antimalarials should therefore be investigated for both treatment and chemoprophylaxis against falciparum parasites in Pakistan.