Structure of the K74 antigen from Escherichia coli O44:K74:H18, a capsular polysaccharide containing furanosidic beta-KDO residues.

The structure of the capsular K74 antigen of E. coli H702c (O44:K74:H18) was elucidated by determination of the composition, 1H- and 13C-n.m.r. and c.d. spectroscopy, periodate oxidation, and methylation analysis of the polysaccharide and of a trisaccharide obtained by mild acid hydrolysis. The K74 antigen has the repeating unit----3)-beta-D-Ribf-(1----2)-beta-D-Ribf-(1----6)-beta-++ +KDOf-(2----. Of the repeating units, approximately 65% are O-acetylated, most probably at C-2 of the 3-linked ribose.