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Sasithon Pukrittayakamee

Other affiliations: John Radcliffe Hospital, Novartis, University of Oxford  ...read more
Bio: Sasithon Pukrittayakamee is an academic researcher from Mahidol University. The author has contributed to research in topics: Malaria & Plasmodium falciparum. The author has an hindex of 60, co-authored 195 publications receiving 11873 citations. Previous affiliations of Sasithon Pukrittayakamee include John Radcliffe Hospital & Novartis.


Papers
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Journal ArticleDOI
TL;DR: Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing, and the incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission.
Abstract: BACKGROUND: Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and now poses a threat to the control and elimination of malaria. Mapping the geographic extent of resistance is essential for planning containment and elimination strategies. METHODS: Between May 2011 and April 2013, we enrolled 1241 adults and children with acute, uncomplicated falciparum malaria in an open-label trial at 15 sites in 10 countries (7 in Asia and 3 in Africa). Patients received artesunate, administered orally at a daily dose of either 2 mg per kilogram of body weight per day or 4 mg per kilogram, for 3 days, followed by a standard 3-day course of artemisinin-based combination therapy. Parasite counts in peripheral-blood samples were measured every 6 hours, and the parasite clearance half-lives were determined. RESULTS: The median parasite clearance half-lives ranged from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand-Cambodia border. Slowly clearing infections (parasite clearance half-life >5 hours), strongly associated with single point mutations in the "propeller" region of the P. falciparum kelch protein gene on chromosome 13 (kelch13), were detected throughout mainland Southeast Asia from southern Vietnam to central Myanmar. The incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission. In western Cambodia, where artemisinin-based combination therapies are failing, the 6-day course of antimalarial therapy was associated with a cure rate of 97.7% (95% confidence interval, 90.9 to 99.4) at 42 days. CONCLUSIONS: Artemisinin resistance to P. falciparum, which is now prevalent across mainland Southeast Asia, is associated with mutations in kelch13. Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing. (Funded by the U.K. Department of International Development and others; ClinicalTrials.gov number, NCT01350856.).

1,777 citations

Journal ArticleDOI
TL;DR: Assessment of the spread of artemisinin-resistant P falciparum in Myanmar finds Artemisinin resistance extends across much of Myanmar, and Appropriate therapeutic regimens should be tested urgently and implemented comprehensively if spread of warfarin resistance to other regions is to be avoided.
Abstract: Summary Background Emergence of artemisinin resistance in southeast Asia poses a serious threat to the global control of Plasmodium falciparum malaria. Discovery of the K13 marker has transformed approaches to the monitoring of artemisinin resistance, allowing introduction of molecular surveillance in remote areas through analysis of DNA. We aimed to assess the spread of artemisinin-resistant P falciparum in Myanmar by determining the relative prevalence of P falciparum parasites carrying K13-propeller mutations. Methods We did this cross-sectional survey at malaria treatment centres at 55 sites in ten administrative regions in Myanmar, and in relevant border regions in Thailand and Bangladesh, between January, 2013, and September, 2014. K13 sequences from P falciparum infections were obtained mainly by passive case detection. We entered data into two geostatistical models to produce predictive maps of the estimated prevalence of mutations of the K13 propeller region across Myanmar. Findings Overall, 371 (39%) of 940 samples carried a K13-propeller mutation. We recorded 26 different mutations, including nine mutations not described previously in southeast Asia. In seven (70%) of the ten administrative regions of Myanmar, the combined K13-mutation prevalence was more than 20%. Geospatial mapping showed that the overall prevalence of K13 mutations exceeded 10% in much of the east and north of the country. In Homalin, Sagaing Region, 25 km from the Indian border, 21 (47%) of 45 parasite samples carried K13-propeller mutations. Interpretation Artemisinin resistance extends across much of Myanmar. We recorded P falciparum parasites carrying K13-propeller mutations at high prevalence next to the northwestern border with India. Appropriate therapeutic regimens should be tested urgently and implemented comprehensively if spread of artemisinin resistance to other regions is to be avoided. Funding Wellcome Trust–Mahidol University–Oxford Tropical Medicine Research Programme and the Bill & Melinda Gates Foundation.

385 citations

Journal ArticleDOI
23 Jan 2015-Science
TL;DR: Analysis of in vivo transcriptomes of P. falciparum isolates from patients with acute malaria found that artemisinin resistance is associated with increased expression of unfolded protein response (UPR) pathways involving the major PROSC and TRiC chaperone complexes.
Abstract: Artemisinin resistance in Plasmodium falciparum threatens global efforts to control and eliminate malaria. Polymorphisms in the kelch domain-carrying protein K13 are associated with artemisinin resistance, but the underlying molecular mechanisms are unknown. We analyzed the in vivo transcriptomes of 1043 P. falciparum isolates from patients with acute malaria and found that artemisinin resistance is associated with increased expression of unfolded protein response (UPR) pathways involving the major PROSC and TRiC chaperone complexes. Artemisinin-resistant parasites also exhibit decelerated progression through the first part of the asexual intraerythrocytic development cycle. These findings suggest that artemisinin-resistant parasites remain in a state of decelerated development at the young ring stage, whereas their up-regulated UPR pathways mitigate protein damage caused by artemisinin. The expression profiles of UPR-related genes also associate with the geographical origin of parasite isolates, further suggesting their role in emerging artemisinin resistance in the Greater Mekong Subregion.

378 citations

Journal ArticleDOI
TL;DR: It is proposed that P. ovale comprises 2 nonrecombining species that are sympatric in Africa and Asia and speculate on possible scenarios that could have led to this speciation.
Abstract: Background: Malaria in humans is caused by apicomplexan parasites belonging to 5 species of the genus Plasmodium. Infections with Plasmodium ovale are widely distributed but rarely investigated, and the resulting burden of disease is not known. Dimorphism in defined genes has led to P. ovale parasites being divided into classic and variant types. We hypothesized that these dimorphs represent distinct parasite species. Methods: Multilocus sequence analysis of 6 genetic characters was carried out among 55 isolates from 12 African and 3 Asia-Pacific countries. Results: Each genetic character displayed complete dimorphism and segregated perfectly between the 2 types. Both types were identified in samples from Ghana, Nigeria, Sao Tome, Sierra Leone, and Uganda and have been described previously in Myanmar. Splitting of the 2 lineages is estimated to have occurred between 1.0 and 3.5 million years ago in hominid hosts. Conclusions: We propose that P. ovale comprises 2 nonrecombining species that are sympatric in Africa and Asia. We speculate on possible scenarios that could have led to this speciation. Furthermore, the relatively high frequency of imported cases of symptomatic P. ovale infection in the United Kingdom suggests that the morbidity caused by ovale malaria has been underestimated.

342 citations

Journal ArticleDOI
TL;DR: In epidemiological studies, a high prevalence of cryptic mixed-malaria species infection has been detected by sensitive PCR techniques and these interactions have important clinical and public health implications.

279 citations


Cited by
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TL;DR: Changing the use of tetracyclines in human and animal health as well as in food production is needed if this class of broad-spectrum antimicrobials through the present century is to continue to be used.
Abstract: Tetracyclines were discovered in the 1940s and exhibited activity against a wide range of microorganisms including gram-positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and protozoan parasites. They are inexpensive antibiotics, which have been used extensively in the prophlylaxis and therapy of human and animal infections and also at subtherapeutic levels in animal feed as growth promoters. The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953. Tetracycline resistance now occurs in an increasing number of pathogenic, opportunistic, and commensal bacteria. The presence of tetracycline-resistant pathogens limits the use of these agents in treatment of disease. Tetracycline resistance is often due to the acquisition of new genes, which code for energy-dependent efflux of tetracyclines or for a protein that protects bacterial ribosomes from the action of tetracyclines. Many of these genes are associated with mobile plasmids or transposons and can be distinguished from each other using molecular methods including DNA-DNA hybridization with oligonucleotide probes and DNA sequencing. A limited number of bacteria acquire resistance by mutations, which alter the permeability of the outer membrane porins and/or lipopolysaccharides in the outer membrane, change the regulation of innate efflux systems, or alter the 16S rRNA. New tetracycline derivatives are being examined, although their role in treatment is not clear. Changing the use of tetracyclines in human and animal health as well as in food production is needed if we are to continue to use this class of broad-spectrum antimicrobials through the present century.

3,647 citations

Journal ArticleDOI
TL;DR: The overall median clearance times were 84 hours (interquartile range, 60 to 96) in Pailin and 48 hours in Wang Pha (P<0.001) in each of the two locations as discussed by the authors.
Abstract: We studied 40 patients in each of the two locations. The overall median parasite clearance times were 84 hours (interquartile range, 60 to 96) in Pailin and 48 hours (interquartile range, 36 to 66) in Wang Pha (P<0.001). Recrudescence confirmed by means of polymerase-chain-reaction assay occurred in 6 of 20 patients (30%) receiving artesunate monotherapy and 1 of 20 (5%) receiving artesunate–mefloquine therapy in Pailin, as compared with 2 of 20 (10%) and 1 of 20 (5%), respectively, in Wang Pha (P = 0. 31). These markedly different parasitologic responses were not explained by differences in age, artesunate or dihydroartemisinin pharmacokinetics, results of isotopic in vitro sensitivity tests, or putative molecular correlates of P. falciparum drug resistance (mutations or amplifications of the gene encoding a multidrug resistance protein [PfMDR1] or mutations in the gene encoding sarco–endoplasmic reticulum calcium ATPase6 [PfSERCA]). Adverse events were mild and did not differ significantly between the two treatment groups. CONCLUSIONS P. falciparum has reduced in vivo susceptibility to artesunate in western Cambodia as compared with northwestern Thailand. Resistance is characterized by slow parasite clearance in vivo without corresponding reductions on conventional in vitro susceptibility testing. Containment measures are urgently needed. (ClinicalTrials.gov number, NCT00493363, and Current Controlled Trials number, ISRCTN64835265.)

3,010 citations

Journal ArticleDOI
10 Mar 2005-Nature
TL;DR: It is estimated that there were 515 (range 300–660) million episodes of clinical P. falciparum malaria in 2002, up to 50% higher than those reported by the World Health Organization and 200% higher for areas outside Africa, reflecting the WHO's reliance upon passive national reporting for these countries.
Abstract: Interest in mapping the global distribution of malaria is motivated by a need to define populations at risk for appropriate resource allocation and to provide a robust framework for evaluating its global economic impact. Comparison of older and more recent malaria maps shows how the disease has been geographically restricted, but it remains entrenched in poor areas of the world with climates suitable for transmission. Here we provide an empirical approach to estimating the number of clinical events caused by Plasmodium falciparum worldwide, by using a combination of epidemiological, geographical and demographic data. We estimate that there were 515 (range 300-660) million episodes of clinical P. falciparum malaria in 2002. These global estimates are up to 50% higher than those reported by the World Health Organization (WHO) and 200% higher for areas outside Africa, reflecting the WHO's reliance upon passive national reporting for these countries. Without an informed understanding of the cartography of malaria risk, the global extent of clinical disease caused by P. falciparum will continue to be underestimated.

2,825 citations