Abstract. Burkholderia pseudomallei causes melioidosis, the third most common cause of death from infectious diseases in northeast Thailand. Four physicochemical factors were set so that their values covered the range of the northeast, which is an endemic area. The soil pH was set at pH 4-10, soil salinity was 0.0-5.0% NaCl, total iron was 50-150 mg/kg soil, and carbon to nitrogen ratio (C/N) was 10:1 to 40:1. The experiments were carried out at 37 C, and soil moisture was maintained for 7 days. The number of viable bacterial cells was counted daily. Soil pH, salinity, Fe, and C/N ratio affected the bacterial growth. The bacterial colony was significantly (P 0.05) reduced at soil pH 8, soil salinity 1% NaCl, and C/N ratio 40:1. However, the growth of B. pseudomallei was enhanced by increasing the concentrations of iron significantly (P 0.05). We propose using these findings to control B. pseudomallei in situ.

The environmental Gram negative bacteria Burkholderia pseudomallei, the causative agent of melioidosis, have been found globally. B. pseudomallei can survive under a wide range of environmental conditions and is isolated from soil in both rainy and dry seasons. The correlation of melioidosis cases have been predominantly found present in B. pseudomallei during rainfall. In the present study, various physicochemical properties of soil in rainy and dry seasons in Khon Kaen, Thailand, where melioidosis is endemic, were investigated for their correlations with the presence of B. pseudomallei. The results revealed that the mean soil pH of 6.05, the low percentage of water holding capacity (%WHC) and the low iron (Fe) were significantly correlated with the presence of B. pseudomallei (p < 0.05) in the rainy season, while high concentration of manganese (Mn) was correlated with the presence of this bacterium in dry season (p < 0.05). These data will be useful in the control of B. pseudomallei in the environment to reduce melioidosis cases.