Lipopolysaccharide size and distribution determine serum resistance in Salmonella montevideo

Abstract

The survival of Salmonella montevideo during serum treatment depends on the presence of an 0 antigen (0-Ag) associated with the lipopolysaccharide molecule. In this organism, the 0 antigen is a polysaccharide composed of 0 to more than 55 subunits, each containing 4 mannose residues together with glucose and n-acetylglucosamine. We used a mutant strain of S. montevideo that smooth, enteric gram-negative bacteria is efficient, and the bactericidal C5b-9 complex is formed on the surface of such smooth cells (13). However, in contrast to the stable, hydrophobic interaction of C5b-9 with rough cells, the C5b-9 complex is bound by weak hydrophilic interactions to smooth cells and is released from the surface (14). Consequently, it is not bactericidal. We and others (13,14,36) have suggested that C5b-9 complexes are shed because complement activation takes place on long O-Ag side chains and that C5b-9 complexes formed are sterically inhibited from inserting into hydrophobic membrane domains. In a recent paper (12)

Regulation of O‐antigen chain length is required for Shigella flexneri virulence

“…Although the data relate to the use of model systems, we cannot, of course, rule out the possibility that the observed effect may not be relevant to infection of humans. Nevertheless, the data on the rol::Km and rfbD::Km mutants, together with those of others using other mutants affecting LPS synthesis, show that O-antigen has a very important role in pathogenesis rather than only acting passively in the evasion of host defence mechanisms (Grossman et al, 1987;Joiner et al, 1982a,b;Liang-Takasaki et al, 1982). The data presented demonstrate that the mere presence of an O-antigen is insufficient for virulence, and that maintenance of a modal LPS O-antigen chain length distribution is essential for full virulence.…”

Heterogeneity of lipopolysaccharides from Pseudomonas aeruginosa: analysis of lipopolysaccharide chain length

“…2 and 3, respectively) of the LPS molecules in the low-molecular-weight population and 30 to 50% in the high-molecular-weight fractions (36,48). It (47), antibiotic susceptibility (la, 4, 18), LPS aggregate structure (47), bacteriophage recognition (25,27), immunochemical characterization (8,9,49), virulence (11,50), protection against the bactericidal action of serum (21,41), polyclonal B cell aativation, and macrophage cytotoxicity (43). The low level of LPS on P. aeruginosa that contains a long 0 polymer, however, may be sufficient to form a uniform cover over the cell, since the surface is inaccessible to rough-core-specific monoclonal antibodies (52).…”

The PmrA/PmrB regulatory system controls the expression of the wzzfepE gene involved in the O-antigen synthesis of Salmonella enterica serovar Typhimurium

“…The O-Ag chain length was previously correlated with bacterial virulence in mice as well as resistance to phagocytosis, cationic peptides and iron (Burns & Hull, 1998;Joiner, 1985;Skurnik & Bengoechea, 2003). Furthermore, several studies have determined that in Salmonella the O-Ag is involved in resistance to the bactericidal activity of serum complement (Grossman et al, 1987;Joiner, 1985;Tomás et al, 1988). Murray et al (2005) reported enhanced survival of bacteria in serum when the VL O-Ag was increased by previous exposure to inactivated pig serum or iron limitation; however, this effect could not be correlated with change in the expression of the wzz fepE gene.…”