In vitro drug sensitivity testing in Plasmodium vivax

Background: In Thailand, the proportion of Plasmodium vivax infection has become equal to Plasmodium falciparum. Reports of a trend of gradual decline of in vitro sensitivity of P. vivax to chloroquine in some areas of the country, together with accumulating evidences of chloroquine resistance P. vivax in other parts of the world, emphasize the need for closely and continuously monitoring clinical efficacy in conjunction with in vitro sensitivity of P. vivax isolates. Methods: The study was conducted at Mae Tao clinic for migrant workers, Tak Province during March 2008 -August 2009. A total of 130 patients (17 Thais and 113 Burmeses; 64 males and 66 females) with mono-infection of P. vivax malaria, aged between 15-60 years and weighing more than 40 kg, were included in the study. Patients received treatment with chloroquine (2,000 mg chloroquine phosphate over three days) and the anti-relapse drug primaquine (15 mg for 14 days). In vitro sensitivity of P. vivax isolates was evaluated by schizont maturation inhibition assay. Results: All patients showed satisfactory response to treatment. The cure rate was virtually 100% within the followup period of 42 days. Neither recurrence of P. vivax parasitaemia nor appearance of P. falciparum occurred during the investigation period. In vitro data showed a stable sensitivity of chloroquine in this area since 2006. Geometric mean and median (95% CI) values of IC 50 for chloroquine were 100.1 and 134.7 (1.1-264.9) nM, respectively. Conclusion: In vivo results suggest that the standard regimen of chloroquine was still very effective for the treatment of blood infections with P. vivax in the Thai-Myanmar border area. In vitro sensitivity data however, raise the possibility of potential advent of resistance in the future. Regular monitoring of the chloroquine sensitivity of P. vivax is essential to facilitate the early recognition of treatment failures and to expedite the formulation of appropriate changes to the drug policy.

Section: Discussionmentioning

confidence: 99%

Monitoring of clinical efficacy and in vitro sensitivity of Plasmodium vivax to chloroquine in area along Thai Myanmar border during 2009-2010

Muhamad

Ruengweerayut

Chacharoenkul

et al. 2011

“…Species of Plasmodium tested and the time lag in maturation seen previously ex vivo were allowed for in these assays [8]. While more complex counting procedures have been used to study P. vivax parasites that, like P. knowlesi , have mature parasites present in circulating blood [9], only the timing of assays was altered. This is because the P. knowlesi isolates contained predominantly immature parasites (Table 1) and results from a parallel study on tightly synchronised immature laboratory P. knowlesi H strain parasites with artesunate using the p LDH (see below) and Mark III assays were comparable with each other and with the data derived from isolates (see Results).…”

Section: Methodsmentioning

confidence: 99%

Susceptibility of human Plasmodium knowlesi infections to anti-malarials

Fatih

Staines

Siner

et al. 2013

BackgroundEvidence suggests that Plasmodium knowlesi malaria in Sarawak, Malaysian Borneo remains zoonotic, meaning anti-malarial drug resistance is unlikely to have developed in the absence of drug selection pressure. Therefore, adequate response to available anti-malarial treatments is assumed.MethodsHere the ex vivo sensitivity of human P. knowlesi isolates in Malaysian Borneo were studied, using a WHO schizont maturation assay modified to accommodate the quotidian life cycle of this parasite. The in vitro sensitivities of P. knowlesi H strain adapted from a primate infection to in vitro culture (by measuring the production of Plasmodium lactate dehydrogenase) were also examined together with some assays using Plasmodium falciparum and Plasmodium vivax.ResultsPlasmodium knowlesi is uniformly highly sensitive to artemisinins, variably and moderately sensitive to chloroquine, and less sensitive to mefloquine.ConclusionsTaken together with reports of clinical failures when P. knowlesi is treated with mefloquine, the data suggest that caution is required if using mefloquine in prevention or treatment of P. knowlesi infections, until further studies are undertaken.

“…Plasmodium vivax, Plasmodium malariae and Plasmodium ovale do not cytoadhere, and late trophozoite and schizont stages of these species are found more frequently in peripheral blood [23,24]. However, laboratory studies are usually confined to P. falciparum since continuous culture of the other species is not currently feasible.…”

Section: Introductionmentioning

confidence: 99%

Parameterization of high magnetic field gradient fractionation columns for applications with Plasmodium falciparum infected human erythrocytes

Karl

Davis

Pierre

2010

BackgroundMagnetic fractionation of erythrocytes infected with Plasmodium falicparum has several research uses including enrichment of infected cells from parasite cultures or enhanced detection of P. falciparum gametocytes. The aim of the present study was to quantitatively characterize the magnetic fractionation process and thus enable optimization of protocols developed for specific uses.MethodsSynchronized cultures of P. falciparum parasites incubated with human erythrocytes were magnetically fractionated with commercially available columns. The timing of the fractionation experiments was such that the parasites were in second half of their erythrocytic life cycle with parasite densities ranging from 1 to 9%. Fractionations were carried out in a single pass through the columns. Cells were enumerated and differentiated in the initial samples as well as in the positive and negative fractions. The capture of cells by the fractionation column was described by a saturation binding model.ResultsThe magnetic binding affinity to the column matrix was approximately 350 times greater for infected cells compared with uninfected cells. The purity of infected cells in the captured fraction was generally >80% but decreased rapidly (to less than 50%) when the number of infected cells that passed through the column was substantially decreased (to less than 9 ± 5 × 105 cells). The distribution of captured parasite developmental stages shifted to mature stages as the number of infected cells in the initial samples and flow rate increased. The relationship between the yield of infected cells in the captured fraction and flow rate of cells conformed to a complementary cumulative log-normal equation with flow rates >1.6 × 105 cells per second resulting in yields <50%.ConclusionsA detailed quantitative analysis of a batchwise magnetic fractionation process for malaria infected erythrocytes using high gradient magnetic fractionation columns was performed. The models applied in this study allow the prediction of capture efficiency if the initial infected cell concentration and the flow rate are known.