title: Environmental Free-Living Amoebae Isolated from Soil in Khon Kaen, Thailand, Antagonize Burkholderia pseudomallei.
abstract: Presence of Burkholderia pseudomallei in soil and water is correlated with endemicity of melioidosis in Southeast Asia and northern Australia. Several biological and physico-chemical factors have been shown to influence persistence of B. pseudomallei in the environment of endemic areas. This study was the first to evaluate the interaction of B. pseudomallei with soil amoebae isolated from B. pseudomallei-positive soil site in Khon Kaen, Thailand. Four species of amoebae, Paravahlkampfia ustiana, Acanthamoeba sp., Naegleria pagei, and isolate A-ST39-E1, were isolated, cultured and identified based on morphology, movement and 18S rRNA gene sequence. Co-cultivation combined with a kanamycin-protection assay of B. pseudomallei with these amoebae at MOI 20 at 30°C were evaluated during 0-6 h using the plate count technique on Ashdown's agar. The fate of intracellular B. pseudomallei in these amoebae was also monitored by confocal laser scanning microscopy (CLSM) observation of the CellTracker™ Orange-B. pseudomallei stained cells. The results demonstrated the ability of P. ustiana, Acanthamoeba sp. and isolate A-ST39-E1 to graze B. pseudomallei. However, the number of internalized B. pseudomallei substantially decreased and the bacterial cells disappeared during the observation period, suggesting they had been digested. We found that B. pseudomallei promoted the growth of Acanthamoeba sp. and isolate A-ST39-E1 in co-cultures at MOI 100 at 30°C, 24 h. These findings indicated that P. ustiana, Acanthamoeba sp. and isolate A-ST39-E1 may prey upon B. pseudomallei rather than representing potential environmental reservoirs in which the bacteria can persist.
authors.affiliation: Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.|Melioidosis Research Center, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Parumon
authors.initials: P
authors.lastname: Noinarin
authors.affiliation: Department of Environmental Science, Faculty of Science, Khon Kaen University, Khon Kaen, Thailand.|Melioidosis Research Center, Khon Kaen University, Khon Kaen, Thailand.|Biofilm Research Group, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Pisit
authors.initials: P
authors.lastname: Chareonsudjai
authors.affiliation: Department of Biology, Faculty of Science, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Pinich
authors.initials: P
authors.lastname: Wangsomnuk
authors.affiliation: Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.|Melioidosis Research Center, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Surasak
authors.initials: S
authors.lastname: Wongratanacheewin
authors.affiliation: Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand.|Melioidosis Research Center, Khon Kaen University, Khon Kaen, Thailand.|Biofilm Research Group, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Sorujsiri
authors.identifier: http://orcid.org/0000-0001-7176-2924
authors.initials: S
authors.lastname: Chareonsudjai
mesh_terms: D056894:Amoebozoa / Q000235:genetics / Q000302:isolation & purification / Q000382:microbiology* / Q000648:ultrastructure; D016957:Burkholderia pseudomallei / Q000187:drug effects / Q000302:isolation & purification / Q000502:physiology*; D018613:Microscopy, Confocal; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017423:Sequence Analysis, RNA; D012988:Soil Microbiology; D013785:Thailand; D053058:Trophozoites
chemical_list: D012337:RNA, Ribosomal, 18S