STRUCTURAL AND SEROLOGICAL STUDIES OF LIPOPOLYSACCHARIDES FROM PROPOSED NEW SEROTYPES (O25 AND O26) OF SERRATIA-MARCESCENS

The surface polysaccharides of the two most recently proposed O-seroty pe strains of Serratia marcescens, O25 and O26, were characterised in terms of their chemical structure and immunological reactions. No poly mer was isolated from O25, which was shown to lack both capsular K-ant igen and smooth, O-antigenic lipopolysaccharide. A neutral polysacchar ide was isolated from O26 and shown to be a polymer of rhamnose and N- acetylgalactosamine of the type previously found in the O9 and O15 ref erence strains. Serological cross-reactions among all three strains we re demonstrated by using both whole-cell enzyme-linked immunosorbent a ssay and immunoblotting of lipopolysaccharide resolved by polyacrylami de gel electrophoresis in the presence of sodium dodecyl sulfate. No a cidic polysaccharide was found in O26 and this was consistent with the absence of an immunogenic capsule. Thus, neither strain qualifies for inclusion as a new serotype in either an O-typing or a K-typing schem e.