PSEUDOMONAS-PSEUDOMALLEI ISOLATES COLLECTED OVER 25 YEARS FROM A NONTROPICAL ENDEMIC FOCUS SHOW CLONALITY ON THE BASIS OF RIBOTYPING

Between 1966 and 1991, melioidosis, a disease caused by Pseudomonas ps eudomallei that is mostly confined to tropical regions, occurred in fa rm animals and a farmer in temperate south-west Western Australia. Usi ng an Escherichia coli probe containing a ribosomal RNA operon, P. pse udomallei DNA from isolates from 8 animals, a soil sample and the huma n case showed an identical ribotype on Southern blotting. The ribotype was different from the 3 commonest ribotypes seen in tropical Austral ia. This molecular typing supports the theory of clonal introduction o f P. pseudomallei into a non-endemic region, with environmental contam ination, local dissemination and persistence over 25 years. As melioid osis is often fatal in humans, such persistence in a temperate region is cause for concern.