CHARACTERIZATION OF THE CAPSULAR POLYSACCHARIDE OF BURKHOLDERIA (PSEUDOMONAS) PSEUDOMALLEI 304B

Burkholderia (Pseudomonas) pseudomallei is the causative agent of meli oidosis, a bacterial infection of considerable morbidity in areas of e ndemicity of Southeast Asia and northern Australia. Clinical isolates of B, pseudomallei have been demonstrated to produce a lipopolysacchar ide (LPS) containing two separate and chemically distinct antigenic O polysaccharides against which infected patients produced antibodies, A putative capsular polysaccharide (CPS) has also been reported and is thought to be antigenically conserved based on results of serological studies with clinical B, pseudomallei isolates. In the present study, the CPS isolated from B, pseudomallei 304b from northeastern Thailand was found to have an [alpha](D) of +99 degrees (water), was composed o f D-gatactose (D-Gal), 3-deoxy-D-manno-2-octulosonic acid (KDO), and O -acetyl 3:1:1), and was a linear unbranched polymer of repeating tetra saccharide units having the following structure: ha-D-Galp-(1-3)-beta- D-Galp-(1-5)-beta-D-KDOp-(2-. Sera from 13 of 15 patients with differe nt clinical manifestations of melioidosis but not normal controls reco gnize the CPS, which suggests that it is immunogenic and raises the po ssibility that it may have a role as a vaccine candidate and/or diagno stic agent.