A novel plasmid-encoded serotype conversion mechanism through addition of phosphoethanolamine to the O-antigen of Shigella flexneri

Abstract Shigella flexneri is the major pathogen causing bacillary dysentery in developing countries. S. flexneri is divided into at least 16 serotypes based on the combination of antigenic determinants present in the O-antigen. All the serotypes (except for serotype 6) share a basic O-unit containing one N-acetyl-D-glucosamine and three L-rhamnose residues, whereas differences between the serotypes are conferred by phage-encoded glucosylation and/or O-acetylation. Serotype Xv is a newly emerged and the most prevalent serotype in China, which can agglutinate with both MASF IV-1 and 7,8 monoclonal antibodies. The factor responsible for the presence of MASF IV-1 (E1037) epitope has not yet been identified. In this study, we analyzed the LPS structure of serotype Xv strains and found that the MASF IV-1 positive phenotype depends on an Oantigen modification with a phosphoethanolamine (PEtN) group attached at position 3 of one of the rhamnose residues. A plasmid carried gene, lpt-O (LPS phosphoethanolamine transferase for O-antigen), mediates the addition of PEtN for serotype Xv and other MASF IV-1 positive strains. These findings reveal a novel serotype conversion mechanism in S. flexneri and show the necessity of further extension of the serotype classification scheme recognizing the MASF IV-1 positive strains as distinctive subtypes

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

© 2014 Elsevier Ltd. All rights reserved. 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 1H and 13C 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

Targeting of Formyl Peptide Receptor 2 for in vivo imaging of acute vascular inflammation

© The author(s). Inflammatory conditions are associated with a variety of diseases and can significantly contribute to their pathophysiology. Neutrophils are recognised as key players in driving vascular inflammation and promoting inflammation resolution. As a result, neutrophils, and specifically their surface formyl peptide receptors (FPRs), are attractive targets for non-invasive visualization of inflammatory disease states and studying mechanistic details of the process. Methods: A small-molecule Formyl Peptide Receptor 2 (FPR2/ALX)-targeted compound was combined with two rhodamine-derived fluorescent tags to form firstly, a targeted probe (Rho-pip-C1) and secondly a targeted, pH-responsive probe (Rho-NH-C1) for in vivo applications. We tested internalization, toxicity and functional interactions with neutrophils in vitro for both compounds, as well as the fluorescence switching response of Rho-NH-C1 to neutrophil activation. Finally, in vivo imaging (fluorescent intravital microscopy [IVM]) and therapeutic efficacy studies were performed in an inflammatory mouse model. Results: In vitro studies showed that the compounds bound to human neutrophils via FPR2/ALX without causing internalisation at relevant concentrations. Additionally, the compounds did not cause toxicity or affect neutrophil functional responses (e.g. chemotaxis or transmigration). In vivo studies using IVM showed Rho-pip-C1 bound to activated neutrophils in a model of vascular inflammation. The pH-sensitive (“switchable”) version termed Rho-NH-C1 validated these findings, showing fluorescent activity only in inflammatory conditions. Conclusions: These results indicate a viable design of fluorescent probes that have the ability to detect inflammatory events by targeting activated neutrophils.British Pharmacological Society; Wilkinson Trust; EPSRC; German Research Foundation

Structure of the O-polysaccharide of Erwinia carotovora ssp carotovora GSPB 436

The O-polysaccharide of a phytopathogenic bacterium, Erwinia carotovora ssp. carotovora GSPB 436, was studied by sugar and methylation analysis, along with H-1 and C-13 NMR spectroscopy. The following structure of the branched tetrasaccharide repeating unit of the O-polysaccharide was established: alpha-D-Glcp-(1-->3) down arrow ->3)-beta-L-Rhap-(1-->4)-alpha-L-Rhap-(1-->3)-alpha-D-Fucp-(1--> The O-polysaccharide contains a minor proportion of 4-O-methylrhamnose, which is suggested to terminate the polymer main chain. (C) 2003 Elsevier Ltd. All rights reserved