A polysaccharide derivative composed of repeating disaccharide units, consisting of (1->3)-linked residues of 2,4-diacetamido-2,4-dideoxy-beta-D-quinovose (2,4-diacetamido-2,4,6-trideoxy-beta-D-glucose, bacillosamine) and 2-acetimidoylamino-2-deoxy-beta-D-glucuronic acid.