Soil physicochemical properties related to the presence of Burkholderia pseudomallei.

The incidence of Burkholderia pseudomallei in the soil from north-east Thailand is estimated to be 20-fold higher than that from central Thailand, and is associated with a 10-fold higher incidence of melioidosis in the region than in central Thailand. This study investigated the presence of B. pseudomallei in relation to the physicochemical properties of soil from Khon Kaen province, north-east Thailand. Thirteen districts (54.2%) were positive for B. pseudomallei. From a selected district, B. pseudomallei was cultured from 19 of 50 sites (38%). The soil in this area was predominantly sandy. From the positive sites, the organism was found mainly at a depth of 30 cm (43/68, 63% of isolates) and was significantly associated with certain soil physicochemical parameters, including a pH of 5.0-6.0, a moisture content >10%, and higher chemical oxygen demand and total nitrogen than negative sites (P<0.05). Burkholderia pseudomallei is unevenly distributed in this area, with the pH of the soil being the major determinant of the presence of the organism. The sandy soil type of north-east Thailand can support the survival of B. pseudomallei and allow it to move freely with water flow, and thus readily come in contact with people during the rainy season.