Environmental Surveillance of Burkholderia pseudomallei

The presence of environmental B. pseudomallei in each country was categorized as being (i) definite, (ii) probable, or (iii) possible (Table 1). ‘Definite’ was defined by the detection of B. pseudomallei from the environment using culture or a specific PCR for B. pseudomallei with or without evidence of melioidosis having been acquired in that country. ‘Probable’ was defined when no reports were identified in the published literature of environmental sampling but clinical reports indicated in-country disease acquisition. This drew on data from the most recent reviews of the distribution of human melioidosis [4] , [12] . ‘Possible’ was defined as the detection of B. pseudomallei from the environment using culture or PCR methodology that did not include a confirmatory test for B. pseudomallei in a setting that lacked evidence of melioidosis having been acquired in that area/country. This included several countries where the detection of environmental B. pseudomallei was reported prior to the description of the highly related Burkholderia thailandensis as a separate species in 1998 [13] (link)–[21] (link). Prior to this, B. thailandensis was referred to as ‘non-pathogenic’ or ‘arabinose-positive’ B. pseudomallei[22] (link). B. pseudomallei and B. thailandensis are indistinguishable on the basis of colony morphology, antimicrobial susceptibility pattern and many biochemical tests (arabinose assimilation being an important exception) [22] (link), [23] (link). A few early studies inoculated suspected B. pseudomallei colonies or environmental samples into an animal model to isolate the organism or determine virulence. This would be predicted to distinguish between B. pseudomallei and non-virulent Burkholderia spp. [22] (link), and was accepted as ‘definite’ evidence of B. pseudomallei. The global map showing the distribution of B. pseudomallei was generated by ArcGIS (10.0, Redlands, CA)