Other bacteria may be classified by "K" or capsular antigens.

Encapsulated strains were classified on the basis of their distinct capsular antigens.

It is produced by a serotype of Escherichia coli that contains a capsular antigen called K1.

Durlakowa I, Lachowicz Z, Slopek S. 1967 Serologic characterization of Klebsiella bacilli on the basis of properties of the capsular antigens.

Vi capsular polysaccharide vaccine (ViCPS) is another subunit vaccine (contains the signature polysaccharide linked to the Vi capsular antigen), in this case, against typhoid caused by a the Typhi serotype of Salmonella.