01 ***: p<0.001. Cytotoxicity towards macrophage cell line J774A.1 Results of the macrophage assays above may be

influenced by cytotoxicity of the strain, since strains that kill the macrophages subject themselves to the action of the antibiotic gentamicin in the culture medium. A comparison of cytotoxicity towards the J774A.1 cells after 24 hours is shown in Figure 1. The non-flagellated mutants of S. Dublin and S. Typhimurium were less cytotoxic than the wild type strains, in line learn more with previous observations that flagella influence Salmonella induction of macrophage cell death [19]. The net growth of flagella mutants in the survival assays above could thus be a result of decreased killing of macrophages. The chemotaxis mutants of S. Dublin did not differ significantly

from the wild type strain, while the cheA mutant of S. Typhimurium was slightly, but significantly, less cytotoxic than the wild type strain. Figure 1 Cytotoxicity of strains of S. Dublin (SDu) and S. Typhimurium (STm) in J774A.1 macrophages. Cytotoxicity was measured 24 hours post challenge with flagellar (SDu fliC and STm fliC/fljB) and chemotaxis mutants (cheA and cheB) and the wild type strains. Significant (p<0.05) differences between wild type and mutant strains are shown with *. The cytotoxicity of the two wild type strains was also compared, and this was shown to be statistically different, as indicated by the * in the top of the figure. Wild type S. Dublin was less cytotoxic than wild type S. Typhimurium (Figure 1). To investigate whether this Selleck Salubrinal was related to the flagella type, we provided the fliC mutant of S. Dublin with S. Typhimurium fliC in trans on the plasmid pPR2. The fliC mutant itself was negative with H:p,g (S. Dublin flagella antigen) and H:i, H:2 (S. Typhimurium flagella antigen) by serotyping and Western blot, while the complemented 5-Fluoracil strain was positive Epothilone B (EPO906, Patupilone) with H:i and H:2 typing sera. It was non-motile

but expressed a high number of flagella as demonstrated by electron microscopy (data not shown). It did not differ significantly from the wild type strain in interactions with epithelial cells or macrophages (data not shown). The complemented fliC mutant of S. Dublin was significantly more cytotoxic than the wild type strain of S. Dublin, above the level of the wild type strain of S. Typhimurium (Figure 1). The importance of chemotaxis and flagella genes for induction of oxidative burst in macrophages The ability of the strains to stimulate the oxidative burst in J774A.1 cells was investigated. Wild type strains differed in induction of oxidative response in the sense that the wild type strain of S. Typhimurium peaked early compared to the wild type strain of S. Dublin, and showed a significantly lower area under the response curve (AUC). Only relative small differences in the oxidative burst were observed between S. Dublin wild type and mutant strains, and none of the differences were statistically significant (Figure 2).