Structure of the capsular polysaccharide of Acinetobacter baumannii 1053 having the KL91 capsule biosynthesis gene locus.

Acinetobacter baumannii 1053 is the type strain for the maintenance of specific bacteriophage AP22, which infects a fairly broad range of A. baumannii strains circulating in Russian clinics and hospitals. A capsular polysaccharide (CPS) was isolated from cells of strain 1053 and studied by sugar analysis along with 1D and 2D (1)H and (13)C NMR spectroscopy. The following structure of the linear trisaccharide repeating unit was established: -->4)-β-D-ManpNAcA-(1-->4)-β-D-ManpNAcA-(1-->3)-α-D-FucpNAc-(1--> where ManNAcA and FucNAc indicate 2-acetamido-2-deoxymannuronic acid and 2-acetamido-2,6-dideoxygalactose, respectively. A polysaccharide having the same repeating unit but a shorter chain was isolated by the phenol-water extraction of bacterial cells. Sequencing of the CPS biosynthesis gene locus showed that A. baumannii 1053 belongs to a new group designated KL91. The gene functions assigned putatively by a comparison with available databases were in agreement with the CPS structure established.