Structure and serological properties of the capsular K11 antigen of Escherichia coli O13:K11:H11.

The capsular K11 antigen of Escherichia coli contains glucose, fructose, and phosphate in the molar ratios 2:1:1, and a backbone of -4)-beta-D-glucopyranosyl-(1----4)-alpha-D-glucopyranosyl phosphate-(1----to which beta-D-fructofuranose is linked at position 3 of the beta-D-glucopyranosyl residue. The fructose, which is the immunodominant sugar of the K11 antigen, is released from the polysaccharide under mild acidic conditions (70 degrees, pH 5.0).