RESEARCH ARTICLE Presence of B. thailandensis and B. thailandensis expressing B. pseudomallei-like capsular polysaccharide in Thailand, and their associations with serological response to B. pseudomallei Viriya Hantrakun 1 , Janjira Thaipadungpanit 1 , Patpong Rongkard 1 , Prapaporn Srilohasin 1 , Premjit Amornchai 1 , Sayan Langla 1 , Mavuto Mukaka 1,2 , Narisara Chantratita 1,3 , Vanaporn Wuthiekanun 1 , David A. B. Dance 2,4,5 , Nicholas P. J. Day 1,2 , Sharon J. Peacock 1,3,4,6 , Direk Limmathurotsakul 1,2,7 * 1 Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand, 2 Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, Old Road Campus, University of Oxford, Oxford, United Kingdom, 3 Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand, 4 London School of Hygiene and Tropical Medicine, London, United Kingdom, 5 Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao People’s Democratic Republic, 6 Department of Medicine, University of Cambridge, Cambridge, United Kingdom, 7 Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand * direk@tropmedres.ac Abstract Background Burkholderia pseudomallei is an environmental Gram-negative bacillus and the cause of melioidosis. B. thailandensis, some strains of which express a B. pseudomallei-like capsular polysaccharide (BTCV), is also commonly found in the environment in Southeast Asia but is considered non-pathogenic. The aim of the study was to determine the distribution of B. thai- landensis and its capsular variant in Thailand and investigate whether its presence is associ- ated with a serological response to B. pseudomallei. Methodology/principal findings We evaluated the presence of B. pseudomallei and B. thailandensis in 61 rice fields in North- east (n = 21), East (n = 19) and Central (n = 21) Thailand. We found BTCV in rice fields in East and Central but not Northeast Thailand. Fourteen fields were culture positive for B. pseudomallei alone, 8 for B. thailandensis alone, 11 for both B. pseudomallei and B. thailan- densis, 6 for both B. thailandensis and BTCV, and 5 for B. pseudomallei, B. thailandensis and BTCV. Serological testing using the indirect hemagglutination assay (IHA) of 96 farmers who worked in the study fields demonstrated that farmers who worked in B. pseudomallei- positive fields had higher IHA titers than those who worked in B. pseudomallei-negative fields (median 1:40 [range: <1:10–1:640] vs. <1:10 [range: <1:10–1:320], p = 0.002). In a PLOS Neglected Tropical Diseases | https://doi.org/10.1371/journal.pntd.0006193 January 24, 2018 1 / 14 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Hantrakun V, Thaipadungpanit J, Rongkard P, Srilohasin P, Amornchai P, Langla S, et al. (2018) Presence of B. thailandensis and B. thailandensis expressing B. pseudomallei-like capsular polysaccharide in Thailand, and their associations with serological response to B. pseudomallei. PLoS Negl Trop Dis 12(1): e0006193. https://doi.org/10.1371/journal. pntd.0006193 Editor: Bradley R. Borlee, Colorado State University, UNITED STATES Received: September 4, 2017 Accepted: December 27, 2017 Published: January 24, 2018 Copyright: © 2018 Hantrakun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All 3 files are available from the Figshare database(https:// figshare.com/s/9ad409f0d16f3845076a). Funding: The study was funded by the National Institute of Allergy and Infectious Diseases (Y1-AI- 4906-09). DL is supported by an Intermediate Fellowship awarded by the Wellcome Trust (101103/Z/13/Z) and DABD by Wellcome Trust