STRUCTURAL AND SEROLOGICAL CHARACTERIZATION OF THE O-SPECIFIC POLYSACCHARIDE OF THE LIPOPOLYSACCHARIDE FROM PROPOSED NEW SEROTYPE O29 OF SERRATIA-MARCESCENS

The structure of the repeating unit of the O-antigenic polysaccharide from the lipopolysaccharide (LPS) of Serratia marcescens strain 111 wa s determined by compositional and methylation analyses and NMR spectro scopy as hap-(1-->2)-alpha-L-Rhap-(1-->2)-alpha-L-Rhap(1--> (Rha, rham nose) which represents a new O-antigenic structure in LPS of S. marces cens but is similar to the structure of the repeating unit of the O-an tigen of S. marcescens O18 Rhap(1-->2)-alpha-L-Rhap(1-->2)-alpha-L-Rha p-(1--> (Oxley D., Wilkinson S.G. Structure of a neutral polymer isola ted from the lipopolysaccharide of the reference strain for S. marcesc ens serogroup O18. Carbohydr Res 1989; 195: 111-115). Serological inve stigations using S. marcescens O- and K-specific ELISA tests and immun oblotting showed that S111 reacted with anti-O18 and anti-K4 sera, and that the anti-S111 serum reacted with serotype strain O18. The K4 rea ction was confirmed as capsular by the Quellung reaction. After absorp tion with the heterologous strain, S. marcescens O18 and strain 111 we re shown to be immunologically distinct, probably because of the prese nce of the GlcNAc residue in O18. We propose to add S111 to the O-sero type strains of S. marcescens as O29.