Immuno-electronmicroscopic demonstration of capsules on group-B streptococci of new serotypes and type candidates.

The location of type polysaccharides on the cells of reference strains of group-B streptococci of serotypes IV and V and new type candidates NT6 and 7271 was investigated by electronmicroscopy of the bacteria after incubation with homologous type-specific antiserum. A distinct capsular layer was found on the surface of the cells of all these strains. Sialic acid, an integral part of all the conventional type polysaccharides of group-B streptococci, was also detected in all the strains examined.