Dr Direk Limmathurotsakul

Research Area: Microbiology
Technology Exchange: Bioinformatics and Medical statistics
Scientific Themes: Tropical Medicine & Global Health and Clinical Trials & Epidemiology
Keywords: Infection, Immunology, Microbiology, Bioinformatics, Clinical Epidemiology and Infectious Diseases
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Between 2010 and 2012, I led a series of studies under the project grant, “Determining routes of B. pseudomallei infection and development of evidence-based guidelines for the prevention of melioidosis” awarded by the Wellcome Trust (Ref 090219/Z/09/Z). I demonstrated for the first time that ingestion and inhalation are important routes of melioidosis infection in northeast Thailand. I also developed the first evidence-based guidelines for the prevention of melioidosis suitable for people living in endemic areas. Conducting a large survey, I showed that 72% of Thais had not heard of melioidosis, and the remaining 28% did not know how to protect themselves from infection. Focus group interviews suggested that modification of activities at risk should be performed by small group education. Using mathematical model, I estimated that an educational programme would be cost-effective if it could reduce the incidence of melioidosis by 25%.

From Jan 2012 onwards, I have been Head of Microbiology Department at MORU. I spend 20% of my time facilitating the research work of other researchers in the department, and spend 80% of my time performing my own research programme under the project grant described above. Following the outcomes of the project grant, I initiated public engagement work at both local and global levels. In Mar 2012, I formed the Thailand Melioidosis Network comprising lead melioidosis researchers in Thailand and representatives from the Ministry of Public Health (MoPH), Thailand. The recommendations provided by the network are now being considered by the Senior Advisory Committee, MoPH, Thailand (http://www.melioidosis.info/th [in Thai]). In May 2012, I launched the first public engagement campaign for melioidosis in Thailand jointly organized by the network and MoPH, Thailand, whichwas a video clip contest entitled “Melioidosis, an infectious disease that Thais must know” (http://www.facebook.com/melioid [in Thai]). I also initiated the World Melioidosis Network among lead melioidosis researchers worldwide (http://www.melioidosis.info [in English]). The World Melioidosis Network developed the first consensus guidelines for the detection of B. pseudomallei in soil. The goal of the global network is to encourage people worldwide to participate in an effort to produce a comprehensive global map of environmental B. pseudomallei.

There are no collaborations listed for this principal investigator.

Chantratita N, Tandhavanant S, Myers ND, Chierakul W, Wuthiekanun V, Mahavanakul W, Limmathurotsakul D, Peacock SJ, West TE. 2014. Common TLR1 genetic variation is not associated with death from melioidosis, a common cause of sepsis in rural Thailand. PLoS ONE, 9 (1), pp. e83285. Read abstract

Melioidosis, infection caused by the Gram-negative bacterium Burkholderia pseudomallei, is a common cause of sepsis in northeast Thailand. In white North Americans, common functional genetic variation in TLR1 is associated with organ failure and death from sepsis. We hypothesized that TLR1 variants would be associated with outcomes in Thais with melioidosis. We collated the global frequencies of three TLR1 variants that are common in white North American populations: rs5743551 (-7202A/G), rs4833095 (742A/G), and rs5743618 (1804G/T). We noted a reversal of the minor allele from white North American subjects to Asian populations that was particularly pronounced for rs5743618. In the Utah residents of European ancestry, the frequency of the rs5743618 T allele was 17% whereas in Vietnamese subjects the frequency was >99%. We conducted a genetic association study in 427 patients with melioidosis to determine the association of TLR1 variation with organ failure or death. We genotyped rs5743551 and rs4833095. The variants were in high linkage disequilibrium but neither variant was associated with organ failure or in-hospital death. In 300 healthy Thai individuals we further tested the association of TLR1 variation with ex vivo blood responses to Pam3CSK4, a TLR1 agonist. Neither variant was robustly associated with blood cytokine responses induced by Pam3CSK4. We identified additional common variation in TLR1 by searching public databases and the published literature and screened three additional TLR1 variants for associations with Pam3CSK4-induced responses but found none. We conclude that the genetic architecture of TLR1 variation differs substantially in southeast Asians compared to other populations and common variation in TLR1 in Thais is not associated with outcome from melioidosis or with altered blood responses to Pam3CSK4. Our findings highlight the need for additional studies of TLR1 and other innate immune genetic modulators of the inflammatory host response and determinants of sepsis in southeast Asian populations. Hide abstract

Jarvis JN, Bicanic T, Loyse A, Namarika D, Jackson A, Nussbaum JC, Longley N, Muzoora C et al. 2014. Determinants of mortality in a combined cohort of 501 patients with HIV-associated Cryptococcal meningitis: implications for improving outcomes. Clin. Infect. Dis., 58 (5), pp. 736-45. Read abstract

BACKGROUND:  Cryptococcal meningitis (CM) is a leading cause of death in individuals infected with human immunodeficiency virus (HIV). Identifying factors associated with mortality informs strategies to improve outcomes. METHODS:  Five hundred one patients with HIV-associated CM were followed prospectively for 10 weeks during trials in Thailand, Uganda, Malawi, and South Africa. South African patients (n = 266) were followed for 1 year. Similar inclusion/exclusion criteria were applied at all sites. Logistic regression identified baseline variables independently associated with mortality. RESULTS:  Mortality was 17% at 2 weeks and 34% at 10 weeks. Altered mental status (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.7-5.9), high cerebrospinal fluid (CSF) fungal burden (OR, 1.4 per log10 colony-forming units/mL increase; 95% CI, 1.0-1.8), older age (>50 years; OR, 3.9; 95% CI, 1.4-11.1), high peripheral white blood cell count (>10 × 10(9) cells/L; OR, 8.7; 95% CI, 2.5-30.2), fluconazole-based induction treatment, and slow clearance of CSF infection were independently associated with 2-week mortality. Low body weight, anemia (hemoglobin <7.5 g/dL), and low CSF opening pressure were independently associated with mortality at 10 weeks in addition to altered mental status, high fungal burden, high peripheral white cell count, and older age. In those followed for 1 year, overall mortality was 41%. Immune reconstitution inflammatory syndrome occurred in 13% of patients and was associated with 2-week CSF fungal burden (P = .007), but not with time to initiation of antiretroviral therapy (ART). CONCLUSIONS:  CSF fungal burden, altered mental status, and rate of clearance of infection predict acute mortality in HIV-associated CM. The results suggest that earlier diagnosis, more rapidly fungicidal amphotericin-based regimens, and prompt immune reconstitution with ART are priorities for improving outcomes. Hide abstract

Limmathurotsakul D, Holden MT, Coupland P, Price EP, Chantratita N, Wuthiekanun V, Amornchai P, Parkhill J, Peacock SJ. 2014. Microevolution of Burkholderia pseudomallei during an acute infection. J. Clin. Microbiol., 52 (9), pp. 3418-21. Read abstract

We used whole-genome sequencing to evaluate 69 independent colonies of Burkholderia pseudomallei isolated from seven body sites of a patient with acute disseminated melioidosis. Fourteen closely related genotypes were found, providing evidence for the rapid in vivo diversification of B. pseudomallei after inoculation and systemic spread. Hide abstract

Myers ND, Chantratita N, Berrington WR, Chierakul W, Limmathurotsakul D, Wuthiekanun V, Robertson JD, Liggitt HD, Peacock SJ, Skerrett SJ, West TE. 2014. The role of NOD2 in murine and human melioidosis. J. Immunol., 192 (1), pp. 300-7. Read abstract

Nucleotide-binding oligomerization domain 2 (NOD2) is a cytosolic pathogen recognition receptor that regulates susceptibility to a variety of infections and chronic diseases. Burkholderia pseudomallei, a facultative intracellular bacterium, causes the tropical infection melioidosis. We hypothesized that NOD2 may participate in host defense in melioidosis. We performed a series of in vitro assays and in vivo experiments and analyzed the association of human genetic variation with infection to delineate the contribution of NOD2 to the host response to B. pseudomallei. We found that transfection with NOD2 mediated NF-κB activation induced by B. pseudomallei stimulation of HEK293 cells. After low-dose inoculation with aerosolized B. pseudomallei, Nod2-deficient mice showed impaired clinical responses and permitted greater bacterial replication in the lung and dissemination to the spleen compared with wild-type mice. IL-6 and KC levels were higher in the lungs of Nod2-deficient mice. In a cohort of 1562 Thai subjects, a common genetic polymorphism in the NOD2 region, rs7194886, was associated with melioidosis, and this effect was most pronounced in women. rs7194886 was not associated with differences in cytokine production induced by whole-blood stimulation with the NOD2 ligand, muramyl dipeptide, or B. pseudomallei. To our knowledge, these findings are the first to characterize the role of NOD2 in host defense in mammalian melioidosis. Hide abstract

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