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Capsular polysaccharide (CPS) was isolated from Acinetobacter baumannii NIPH146, and the following structure of branched pentasaccharide repeating unit was established by sugar analyses along with 1D and 2D NMR spectroscopy: In comparison to most other known capsular polysaccharides of A. baumannii, the CPS studied is neutral and lacks any specific monosaccharide component. The synthesis, assembly and export of this structure could be attributed to genes in a novel capsule biosynthesis gene cluster, designated KL37, which was found in the NIPH146 genome. The CPS of A. baumannii NIPH146 shares the α-d-Galp-(1→6)-β-d-Glcp-(1→3)-d-GalpNAc-(1→ trisaccharide fragment with the CPS units of several A. baumannii strains, including ATCC 17978 and LUH 5537 that carry the KL3 and KL22 gene clusters, respectively. KL37 contains two genes for glycosyltransferases that are related to two glycosyltransferase genes present in both KL3 and KL22, and the encoded proteins could be tentatively assigned to linkages between sugars in the CPS repeat.

Acinetobacter baumannii, capsular polysaccharide structure, glycosyltransferase, K locus, KL37 gene cluster

NCBI PubMed ID: 26057991
Publication DOI: 10.1016/j.carres.2015.05.003
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: Y.A. Knirel gmail.com>
Institutions: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, State Research Center for Applied Microbiology and Biotechnology, Obolensk, Moscow Region, Russia, M. M. Shemyakin and Y. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia, School of Molecular Bioscience, The University of Sydney, Sydney, Australia, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
Methods: 13C NMR, 1H NMR, NMR-2D, sugar analysis, acid hydrolysis, GLC, NMR-1D, bioinformatic analysis

Concerns of Acinetobacter baumannii infection have increased due to the emergence of multi-drug resistance. In the present study, we determined the capsular polysaccharide (CPS) structure of A. baumannii SK44, a clinical isolate from Taiwan, to consist of pentasaccharide repeats. We found that CPS-induced antibody provided 55% protection against challenge in an animal model. The CPS-specific antibody reacted with the surface components of about 62% clinical isolates (342/554 strains) from cross-sectional and longitudinal studies by dot-immunoassay. Pulsed-field gel electrophoresis of positive strains showed the antibody covered different clonalites of A. baumannii clinical isolates. Meanwhile, using the CPS antibody as a probe, we found a number of outer membrane proteins bound to the antibody, including OmpA/motB, TonB-dependent receptor, and Omp38, indicating their association with CPS. These results might lead to the use of the capsular polysaccharide as a vaccine to prevent A. baumannii infection.

Acinetobacter baumannii, capsular polysaccharide, Clinic population distribution, Passive immunity

NCBI PubMed ID: 28190743
Publication DOI: 10.1016/j.vaccine.2017.01.060
Journal NLM ID: 8406899
Publisher: Elsevier
Correspondence: shwu

gate.sinica.edu.tw
Institutions: Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan, National Health Research Institutes, Miaoli County 35053, Taiwan, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan, Department of Emergency Medicine, Taipei Veterans General Hospital, Taipei 112, Taiwan, Human Health Therapeutics, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A0R, Canada, Institute of Microbiology, Tzu Chi University, Hualien 907, Taiwan
Methods: 13C NMR, 1H NMR, methylation, NMR-2D, GC-MS, sugar analysis, acid hydrolysis, MS/MS, serological methods, enzymatic digestion, statistical analysis, SEC, immunization, conjugation, pulsed-field gel electrophoresis (PFGE)