A cluster of melioidosis cases from an endemic region is clonal and is linked to the water supply using molecular typing of Burkholderia pseudomalleiisolates

Nine cases of melioidosis with four deaths occurred over a 28-month period in members of a small remote Aboriginal community in the top end of the Nor thern Territory of Australia. Typing by pulsed-field gel electrophoresis sh owed isolates of Burkholderia pseudomallei from six of the cases to be clon al and also identical to an isolate from the community water supply, but no t to soil isolates. The clonality of the isolates found in this cluster con trasts with the marked genetic diversity of human and environmental isolate s found in this region which is hyperendemic for B. pseudomallei. It is pos sible that the clonal bacteria persisted and were propagated in biofilm in the water supply system. While the exact mode of transmission to humans and the reasons for cessation of the outbreak remain uncertain, contamination of the unchlorinated community water supply is a likely explanation.