Studies of lipopolysaccharides from two strains (C.D.C. 3607-60 and IP 421) of Serratia marcescens O13: structure of the putative O13 antigen.

Structural studies have been carried out on the putative O-specific polysaccharide of the reference strain (C.D.C. 3607-60) for Serratia marcescens O13. Circumstantial evidence that the O13 antigen is a microcapsular, acidic polymer, rather than an integral part of the lipopolysaccharide, has been obtained. Degradative and spectroscopic studies established that the polymer is based on the repeating unit shown, in which the glucuronic acid residue of the linear pentasaccharide carries the lateral 2-acetamido-2-deoxy-beta-D-glucopyranosyl substituent in only about half of the units. The same polymer, again with non-stoichiometric substitution, is also produced by strain IP 421 (O13:H7). The latter strain also produces a neutral polymer which appears to constitute the side chain of the lipopolysaccharide. This polymer, which has a disaccharide repeating-unit of 2-substituted beta-D-ribofuranosyl and 4-substituted 2-acetamido-2-deoxy-alpha-D-galactopyranosyl residues, has been isolated previously from the lipopolysaccharides of the reference strains for S. marcescens serogroups O12 and O14, and appears to be the antigen known to be shared by these strains. (Formula: see text).