Antigenic differences between clinical and environmental isolates of Burkholderia pseudomallei

Burkholderia pseudomallei is a free-living organism that causes the potenti ally lethal tropical infection melioidosis. The disease is endemic in many parts of eastern Asia and northern Australia, The presence of two distinct biotypes in soil can be reliably distinguished by their ability to assimila te L-arabinose, Whereas some soil isolates could utilize this substrate (Ar a(+)), the remaining soil isolates and all clinical isolates tested so far could not (Ara(-)). Only the Ara(-) isolates were virulent in animal models . We have raised a murine monoclonal antibody (MAb) that can readily distin guish Ara(-) from Ara(+) biotypes. The MAb reacted with a high molecular we ight component present only on the Ara(-) biotype. With this MAb, clinical and soil Ara(-) isolates gave identical positive reactions in agglutination , immunofluorescence, ELISA and immunoblot assays, Using these same assay s ystems, the soil Ara(+) biotype did not react with the MAb Similar but dist inct immunoblot patterns were also noted when these two Ara biotypes were p robed with sera from patients with melioidosis or with polyclonal immune ra bbit sera, These data showed that the Ara(-) biotype from both clinical and environmental isolates is antigenically different from its Ara(+) environm ental counterpart, The SDS-PAGE protein and lectin-binding profiles of both groups of Ara(-) isolates were also found to be different from those of th e Ara(+) biotype.