A polysaccharide derivative with a repeating unit consisting of alpha-D-mannosyl, alpha-L-rhamnosyl (acetylated on either O-2 or -3) and alpha-D-galactosyl residues linked sequentially (1->4) and (1->3), to the mannosyl residue is linked (1->3) an alpha-abequosyl residue (partially acetylated on O-2), while to the galactosyl residue is linked (1->4) or (1->6) an alpha-D-glucosyl residue, with all repeating units being linked (1->2). O-polysaccharide repeat from Salmonella Typhimurium (serogroup B).