BACKGROUND: Melioidosis is a frequently fatal infectious disease caused by the 
soil dwelling Gram-negative bacterium Burkholderia pseudomallei. Environmental 
sampling is important to identify geographical distribution of the organism and 
related risk of infection to humans and livestock. The aim of this study was to 
evaluate spatial distribution of B. pseudomallei in soil and consider the 
implications of this for soil sampling strategies.
METHODS AND FINDINGS: A fixed-interval sampling strategy was used as the basis 
for detection and quantitation by culture of B. pseudomallei in soil in two 
environmental sites (disused land covered with low-lying scrub and rice field) 
in northeast Thailand. Semivariogram and indicator semivariogram were used to 
evaluate the distribution of B. pseudomallei and its relationship with range 
between sampling points. B. pseudomallei was present on culture of 80/100 
sampling points taken from the disused land and 28/100 sampling points from the 
rice field. The median B. pseudomallei cfu/gram from positive sampling points 
was 378 and 700 for the disused land and the rice field, respectively (p = 
0.17). Spatial autocorrelation of B. pseudomallei was present, in that samples 
taken from areas adjacent to sampling points that were culture positive 
(negative) for B. pseudomallei were also likely to be culture positive 
(negative), and samples taken from areas adjacent to sampling points with a high 
(low) B. pseudomallei count were also likely to yield a high (low) count. Ranges 
of spatial autocorrelation in quantitative B. pseudomallei count were 11.4 
meters in the disused land and 7.6 meters in the rice field.
CONCLUSIONS: We discuss the implications of the uneven distribution of B. 
pseudomallei in soil for future environmental studies, and describe a range of 
established geostatistical sampling approaches that would be suitable for the 
study of B. pseudomallei that take account of our findings.