O-Antigen-NegativeSalmonella entericaSerovar Typhimurium Is Attenuated in Intestinal Colonization but Elicits Colitis in Streptomycin-Treated Mice

Abstract

Lipopolysaccharide (LPS) is a major constituent of the outer membrane and an important virulence factor of Salmonella enterica subspecies 1 serovar Typhimurium (serovar Typhimurium). To evaluate the role of LPS in eliciting intestinal inflammation in streptomycin-treated mice, we constructed an O-antigen-deficient serovar Typhimurium strain through deletion of the wbaP gene. The resulting strain was highly susceptible to human complement activity and the antimicrobial peptide mimic polymyxin B. Furthermore, it showed a severe defect in motility and an attenuated phenotype in a competitive mouse infection experiment, where the ⌬wbaP strain (SKI12) was directly compared to wild-type Salmonella. Nevertheless, the ⌬wbaP strain (SKI12) efficiently invaded HeLa cells in vitro and elicited acute intestinal inflammation in streptomycin-pretreated mice. Our experiments prove that the presence of complete LPS is not essential for in vitro invasion or for triggering acute colitis.

Effect of Deletion of Genes Involved in Lipopolysaccharide Core and O-Antigen Synthesis on Virulence and Immunogenicity of Salmonella enterica Serovar Typhimurium

“…In general, the trend of sensitivity to the pooled human serum (PHS) followed the length of the LPS, with strains producing longer LPS being more resistant. These data are consistent with a previous study showing that a wbaP mutant was more sensitive to serum than a wild-type strain (30). However, one notable exception was that the ⌬waaG42 mutant, producing the shortest core structure, was as resistant to serum killing as the ⌬waaL mutant, which carries a complete core, and more resistant than mutants with intermediate core structures.…”

Enterobacterial Common Antigen Mutants of Salmonella enterica Serovar Typhimurium Establish a Persistent Infection and Provide Protection against Subsequent Lethal Challenge

“…ECA immunoblotting and LPS/O-antigen silver staining were conducted as follows. Whole-cell lysates were prepared as previously described (27). Briefly, 2 optical density (OD) units/ml of overnight culture were pelleted, resus- , and incubated at 95°C for 15 min.…”

“…For preparation of immunoblots, non-proteinase K-treated lysates were prepared as described above and transferred at a constant current of 200 mA for 3 h using a semidry transfer apparatus (Thermo Scientific, Rochester, NY). Membranes were probed with a 1:10,000 dilution of murine anti-ECA monoclonal antibody 898 (1,27). ECA glycoconjugates were detected using a 1:20,000 dilution of goat anti-mouse IgG conjugated to horseradish peroxidase (Santa Cruz Biotechnology, Santa Cruz, CA).…”

Absence of Poly(ADP-Ribose) Polymerase 1 Delays the Onset of Salmonella enterica Serovar Typhimurium-Induced Gut Inflammation

“…In this model system, streptomycin-pretreated mice develop severe colitis after infection with S. Typhimurium, and the disease largely resembles the human infection. The streptomycin-pretreated mouse model has been used as an appropriate model system to study the mechanisms of pathogenesis and the host responses to acute enteric salmonellosis (10,11,22,27,37).…”