Structural Studies of the Putative O‐Specific Polysaccharide of Acinetobacter baumannii O11

A major polysaccharide containing D-galactose, D-glucose and 2-acetamido-2-deoxy-D-galactose was obtained after mild acid hydrolysis of the water-soluble material released by treatment of cell walls from Acinetobacter baumannii strain O11 with hot, aqueous phenol. By means of NMR studies, Smith degradation and N-deacetylation/deamination, the repeating unit of the polymer was identified as a branched pentasaccharide of the structure shown. Also present was a minor polymer containing glucose, 2-acetamido-2-deoxyglucose-and 2-acetamido-2-deoxygalactose, the structure of which was not elucidated. On serological testing, the polymeric material was shown to correspond to the O-antigenic moiety of the parent extract (assumed to be lipopolysaccharide) and circumstantial evidence indicated that O11 specificity was conferred by the major polymer. [formula: see text]