Publications

It is uncertain whether all adults with bacterial meningitis benefit from treatment with adjunctive dexamethasone.We conducted a randomized, double-blind, placebo-controlled trial of dexamethasone in 435 patients over the age of 14 years who had suspected bacterial meningitis. The goal was to determine whether dexamethasone reduced the risk of death at 1 month and the risk of death or disability at 6 months.A total of 217 patients were assigned to the dexamethasone group, and 218 to the placebo group. Bacterial meningitis was confirmed in 300 patients (69.0%), probable meningitis was diagnosed in 123 patients (28.3%), and an alternative diagnosis was made in 12 patients (2.8%). An intention-to-treat analysis of all the patients showed that dexamethasone was not associated with a significant reduction in the risk of death at 1 month (relative risk, 0.79; 95% confidence interval [CI], 0.45 to 1.39) or the risk of death or disability at 6 months (odds ratio, 0.74; 95% CI, 0.47 to 1.17). In patients with confirmed bacterial meningitis, however, there was a significant reduction in the risk of death at 1 month (relative risk, 0.43; 95% CI, 0.20 to 0.94) and in the risk of death or disability at 6 months (odds ratio, 0.56; 95% CI, 0.32 to 0.98). These effects were not found in patients with probable bacterial meningitis. Results of multivariate analysis indicated that dexamethasone treatment for patients with probable bacterial meningitis was significantly associated with an increased risk of death at 1 month, an observation that may be explained by cases of tuberculous meningitis in the treatment group.Dexamethasone does not improve the outcome in all adolescents and adults with suspected bacterial meningitis; a beneficial effect appears to be confined to patients with microbiologically proven disease, including those who have received prior treatment with antibiotics. (Current Controlled Trials number, ISRCTN42986828 [controlled-trials.com] .).

Dihydroartemisinin-piperaquine is a new, highly effective, and well-tolerated combination treatment for uncomplicated falciparum malaria. The lipophilic characteristic of piperaquine suggests that administration together with fat will increase the oral bioavailability of the drug, and this has been reported for healthy volunteers. This pharmacokinetic study monitored 30 adult patients with uncomplicated falciparum malaria for 4.5 months to evaluate the effects of the concomitant intake of fat on the total piperaquine exposure. The fixed-drug combination of dihydroartemisinin-piperaquine was given with water to fasting patients ( n = 15) or was coadministered with 200 ml milk containing 6.4 g fat ( n = 15). The drug combination was generally well tolerated, and there were no severe adverse effects reported for either group during the study. Total piperaquine exposure (area under the concentration-time curve from zero to infinity [AUC 0-∞ ]; results are given as medians [ranges]) were not statistically different between fed (29.5 h · μg/ml [20.6 to 58.7 h · μg/ml]) and fasting (23.9 h · μg/ml [11.9 to 72.9 h · μg/ml]) patients, but the interindividual variation was reduced in the fed group. Overall, none of the pharmacokinetic parameters differed statistically between the groups. Total piperaquine exposure correlated well with the day 7 concentrations in the fasted group, but the fed group showed a poor correlation. In conclusion, the coadministration of 6.4 g fat did not have any significant effect on piperaquine pharmacokinetics in the treatment of uncomplicated malaria.

Mefloquine is widely used in combination with artemisinin derivatives for the treatment of falciparum malaria. Mefloquine resistance in Plasmodium falciparum has been related to increased copy numbers of multidrug-resistant gene 1 (pfmdr1). We studied the ex vivo dynamics of pfmdr1 gene amplification in culture-adapted P. falciparum in relation to mefloquine resistance and parasite fitness. A Thai P. falciparum isolate (isolate TM036) was assessed by the use of multiple genetic markers as a single genotype. Resistance was selected by exposure to stepwise increasing concentrations of mefloquine up to 30 ng/ml in continuous culture. The pfmdr1 gene copy numbers increased as susceptibility to mefloquine declined (P = 0.03). No codon mutations at positions 86, 184, 1034, 1042, and 1246 in the pfmdr1 gene were detected. Two subclones of selected parasites (average copy numbers, 2.3 and 3.1, respectively) showed a fitness disadvantage when they were grown together with the original parasites containing a single pfmdr1 gene copy in the absence of mefloquine; the multiplication rates were 6.3% and 8.7% lower, respectively (P < 0.01). Modeling of the dynamics of the pfmdr1 copy numbers over time in relation to the relative fitness of the parasites suggested that net pfmdr1 gene amplification from one to two copies occurs once in every 10(8) parasites and that amplification from two to three copies occurs once in every 10(3) parasites. pfmdr1 gene amplification in P. falciparum is a frequent event and confers mefloquine resistance. Parasites with multiple copies of the pfmdr1 gene have decreased survival fitness in the absence of drug pressure.

Mating between relatives often results in negative fitness consequences or inbreeding depression. However, the expression of inbreeding in populations of wild cooperative mammals and the effects of environmental, maternal and social factors on inbreeding depression in these systems are currently not well understood. This study uses pedigree‐based inbreeding coefficients from a long‐term study of meerkats ( Suricata suricatta ) in South Africa to reveal that 44% of the population have detectably non‐zero ( F &gt; 0) inbreeding coefficients. 15% of these inbred individuals were the result of moderate inbreeding ( F ≥ 0.125), although such inbreeding events almost solely occurred when mating individuals had no prior experience of each other. Inbreeding depression was evident for a range of traits: pup mass at emergence from the natal burrow, hind‐foot length, growth until independence and juvenile survival. However, we found no evidence of significant inbreeding depression for skull and forearm length or for pup survival. This research provides a rare investigation into inbreeding in a cooperative mammal, revealing high levels of inbreeding, considerable negative consequences and complex interactions with the social environment.

Background Haematological changes associated with malaria in pregnancy are not well documented, and have focused predominantly on anaemia. Examined here is thrombocytopaenia in pregnant women infected with Plasmodium falciparum or Plasmodium vivax in a low transmission area on the north-western border of Thailand. Methods In this observational study we reviewed the platelet counts from routine complete blood count (CBC) in a cohort of healthy and malaria infected Karen pregnant women attending weekly antenatal clinics. A platelet count of 75,000/μL was the threshold at 2 standard deviations below the mean for healthy pregnant women used to indicate thrombocytopenia. Differences in platelet counts in non-pregnant and pregnant women were compared after matching for age, symptoms, malaria species and parasitaemia. Results In total 974 pregnant women had 1,558 CBC measurements between February 2004 and September 2006. The median platelet counts (/μL) were significantly lower in patients with an episode of falciparum 134,000 [11,000–690,000] (N = 694) or vivax malaria 184,000 [23,000–891,000] (N = 523) compared to healthy pregnant women 256,000 [64,000–781,000] (N = 255), P &lt; 0.05 for both comparisons. Plasmodium falciparum and P. vivax caused a 34% (95% CI 24–47) and 22% (95% CI 8–36) reduction in platelet count, respectively. Pregnant compared to non pregnant women were at higher risk OR = 2.27 (95%CI 1.16–4.4) P = 0.017, for thrombocytopaenia. Platelets counts were higher in first compared with subsequent malaria infections within the same pregnancy. Malaria associated thrombocytopaenia had a median [range] time for recovery of 7 [2–14] days which did not differ by antimalarial treatment (P = 0.86), or species (P = 0.63) and was not associated with active bleeding. Conclusion Pregnant women become more thrombocytopenic than non-pregnant women with acute uncomplicated malaria. Uncomplicated malaria associated thrombocytopaenia is seldom severe. Prompt antimalarial treatment resulted in normalization of platelet counts within a week.

Quantification of artemisinin (ARN) and its derivatives in whole blood has hitherto been thought impossible.A LC-MS/MS method for the analysis of artesunate (ARS), its metabolite dihydroartemisinin (DHA) and artemisinin in human whole blood has been developed and successfully validated. The method includes stabilization of the blood matrix at the time of collection and at the time of analysis. Addition of potassium dichromate to the blood samples deactivated the Fe(2+) core in hemoglobin, while deferoxamine chelated Fe(3+) and prevented back conversion into Fe(2+). A pilot study showed that the blood:plasma ratio for ARS and DHA is approximately 0.75, indicating a significantly lower uptake in red blood cells than had previously been estimated using radiolabeled drug methodology.The developed LC-MS/MS assay is the first method available for quantification of ARN and its derivatives in blood and opens up new possibilities of studying these drugs inside infected red blood cells.

No abstract is provided for this article.

The antimalarial effects of rifampin in 60 adults with Plasmodium vivax malaria were assessed. There were three treatment groups: rifampin (20 and 15 mg/kg of body weight per day for 1 and 4 days, respectively; n = 5); rifampin followed by primaquine (15 mg of base per day for 14 days; n = 25), and chloroquine (25 mg of base per kg over 3 days) followed by primaquine (n = 30). All patients were hospitalized till clearance of fever and parasites, and 45 patients stayed in the hospital for 1 month. Despite initial clearance of fever in all patients and a &gt; or = 6-fold reduction in parasitemia per 48-h life cycle, rifampin alone was not effective: all five patients had subsequent R2-like parasitological responses. All patients treated with rifampin-primaquine cleared both fever and parasitemia, but the therapeutic responses were slower than those following treatment with chloroquine-primaquine. Final fever clearance times were significantly longer (mean [standard deviation] = 43 [35] versus 27 [19] h; P = 0.046), and the parasite clearance times (to 50 and 90% of admission parasite counts and to a level undetectable in a peripheral blood smear) were also significantly greater (P = 0.053 to &lt; 0.001). However, reappearance of infection occurred in only one patient treated with rifampin-primaquine. The results of this study suggest that rifampin at the usual therapeutic doses has partial activity against blood stages of P. vivax in humans but that used alone it is insufficient for cure. Rifampin might therefore be of value in combination antimalarial therapy.

Four carbapenem antibiotics were tested for their in-vitro activities (MICs, MBCs and time-kill studies) against Burkholderia pseudomallei. The carbapenems were all more active than either ceftazidime or co-amoxiclav against strains of B. pseudomallei with a normal susceptibility pattern. Biapenem was the most active antibiotic tested. All four carbapenems retained bactericidal activity against 24 strains of B. pseudomallei with reduced susceptibility to ceftazidime and/or co-amoxiclav.

Aims Resistance to the artemisinins and the artemisinin‐based combination therapy (ACT) partner drugs has developed in Southeast Asia, and artemisinin resistance has also emerged in eastern Africa. Triple ACTs (triple artemisinin‐based combination therapies, TACT), consisting of two partner drugs with different mechanisms of action and similar pharmacokinetic profiles, combined with an artemisinin derivative can help to delay or prevent artemisinin resistance and prolong the useful lifetime of the partner drugs. This study aims to characterize the pharmacokinetic properties of a recommended TACT, artemether‐lumefantrine plus amodiaquine, using data from two large clinical trials. Methods We analysed data from two randomized, controlled intervention trials conducted between 2015 and 2020 in one African country and two Southeast Asian countries, in which artemether‐lumefantrine was administered alone ( n = 443) or together with amodiaquine ( n = 442) to patients with uncomplicated P . falciparum malaria. Both studies included a sub‐cohort with dense pharmacokinetic sampling, combined with sparse data in the other patients. Concentration–time data of artemether, dihydroartemisinin, lumefantrine, desbutyllumefantrine, amodiaquine and desethylamodiaquine were analysed using nonlinear mixed‐effects modelling. Results Pharmacokinetic models were developed for all drugs and demonstrated good predictive performance and goodness‐of‐fit diagnostics. Coadministered amodiaquine was not a significant covariate on pharmacokinetic properties of artemether‐lumefantrine. Model‐predicted C max and AUC (median [95% confidence interval, CI]) for artemether were 256 (159–407) ng/mL and 2850 (1820‐4920) h·ng/mL for artemether‐lumefantrine alone, and 230 (123–391) ng/mL and 2800 (1570‐4570) h·ng/mL for artemether‐lumefantrine‐amodiaquine. For dihydroartemisinin, values were 135 (54.5–214) ng/mL and 1870 (813–3015) h·ng/mL for artemether‐lumefantrine alone, and 116 (40.8–186) ng/mL and 1580 (547–2680) h·ng/mL for artemether‐lumefantrine‐amodiaquine. For lumefantrine, values were 15.2 (2.90–31.3) μg/mL and 600 (275–1230) h·μg/mL for artemether‐lumefantrine alone, and 14.1 (2.72–31.4) μg/mL and 586 (269–1070) h·μg/mL for artemether‐lumefantrine‐amodiaquine. Day 7 concentrations of lumefantrine were 452 (215–1240) and 438 (204–1030) μg/mL for artemether‐lumefantrine alone and artemether‐lumefantrine‐amodiaquine, respectively. All geometric mean ratios (GMRs) for the drug–drug interaction (DDI) effect on key pharmacokinetic parameters of artemether, dihydroartemisinin and lumefantrine fell within the 0.80–1.25 range, with the majority of the corresponding 90% CI also contained within this range. This indicates no clinically relevant DDIs between artemether‐lumefantrine and amodiaquine. Conclusions The DDI effect of amodiaquine on the pharmacokinetics of artemether‐lumefantrine is expected to be minimal, the based on the current analysis. However, further large‐scale clinical trials are needed to confirm this finding.

Background In patients with malaria mixed species infections are common and under reported. In PCR studies conducted in Asia mixed infection rates often exceed 20%. In South-East Asia, approximately one third of patients treated for falciparum malaria experience a subsequent Plasmodium vivax infection with a time interval suggesting relapse. It is uncertain whether the two infections are acquired simultaneously or separately. To determine whether mixed species infections in humans are derived from mainly from simultaneous or separate mosquito inoculations the literature on malaria species infection in wild captured anopheline mosquitoes was reviewed. Methods The biomedical literature was searched for studies of malaria infection and species identification in trapped wild mosquitoes and artificially infected mosquitoes. The study location and year, collection methods, mosquito species, number of specimens, parasite stage examined (oocysts or sporozoites), and the methods of parasite detection and speciation were tabulated. The entomological results in South East Asia were compared with mixed infection rates documented in patients in clinical studies. Results In total 63 studies were identified. Individual anopheline mosquitoes were examined for different malaria species in 28 of these. There were 14 studies from Africa; four with species evaluations in individual captured mosquitoes (SEICM). One study, from Ghana, identified a single mixed infection. No mixed infections were identified in Central and South America (seven studies, two SEICM). 42 studies were conducted in Asia and Oceania (11 from Thailand; 27 SEICM). The proportion of anophelines infected with Plasmodium falciparum parasites only was 0.51% (95% CI: 0.44 to 0.57%), for P. vivax only was 0.26% (95% CI: 0.21 to 0.30%), and for mixed P. falciparum and P. vivax infections was 0.036% (95% CI: 0.016 to 0.056%). The proportion of mixed infections in mosquitoes was significantly higher than expected by chance (P &lt; 0.001), but was one fifth of that sufficient to explain the high rates of clinical mixed infections by simultaneous inoculation. Conclusions There are relatively few data on mixed infection rates in mosquitoes from Africa. Mixed species malaria infections may be acquired by simultaneous inoculation of sporozoites from multiply infected anopheline mosquitoes but this is relatively unusual. In South East Asia, where P. vivax infection follows P. falciparum malaria in one third of cases, the available entomological information suggests that the majority of these mixed species malaria infections are acquired from separate inoculations.