Isolation,structural characterization,and immunological evaluation of a high-molecular-weight exopolysaccharide from Staphylococcus aureus |
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Authors: | Joyce Joseph G Abeygunawardana Chitrananda Xu Qiuwei Cook James C Hepler Robert Przysiecki Craig T Grimm Karen M Roper Keith Ip Charlotte C Yu Cope Leslie Montgomery Donna Chang Mason Campie Sherilyn Brown Martha McNeely Tessie B Zorman Julie Maira-Litrán Tomas Pier Gerald B Keller Paul M Jansen Kathrin U Mark George E |
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Affiliation: | Departments of Virus and Cell Biology, Merck Research Laboratories, WP16-107, P.O. Box 4, West Point, PA 19486, USA. joseph_joyce@merck.com |
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Abstract: | Colonization of implanted medical devices by coagulase-negative staphylococci such as Staphylococcus epidermidis is mediated by the bacterial polysaccharide intercellular adhesin (PIA), a polymer of beta-(1-->6)-linked glucosamine substituted with N-acetyl and O-succinyl constituents. The icaADBC locus containing the biosynthetic genes for production of PIA has been identified in both S. epidermidis and S. aureus. Whereas it is clear that PIA is a constituent that contributes to the virulence of S. epidermidis, it is less clear what role PIA plays in infection with S. aureus. Recently, identification of a novel polysaccharide antigen from S. aureus termed poly N-succinyl beta-(1-->6)-glucosamine (PNSG) has been reported. This polymer was composed of the same glycan backbone as PIA but was reported to contain a high proportion of N-succinylation rather than acetylation. We have isolated a glucosamine-containing exopolysaccharide from the constitutive over-producing MN8m strain of S. aureus in order to prepare polysaccharide-protein conjugate vaccines. In this report we demonstrate that MN8m produced a high-molecular-weight (>300,000 Da) polymer of beta-(1-->6)-linked glucosamine containing 45-60% N-acetyl, and a small amount of O-succinyl (approx 10% mole ratio to monosaccharide units). By detailed NMR analyses of polysaccharide preparations, we show that the previous identification of N-succinyl was an analytical artifact. The exopolysaccharide we have isolated is active in in vitro hemagglutination assays and is immunogenic in mice when coupled to a protein carrier. We therefore conclude that S. aureus strain MN8m produces a polymer that is chemically and biologically closely related to the PIA produced by S. epidermidis. |
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Keywords: | High-molecular-weight exopolysaccharide Staphylococcus aureus Polysaccharide intercellular adhesin |
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