8 ± 5.6 83.4 ± 8.0 SDu cheB 19.5 ± 7.8 2.4 ± 0.9*** SDu fliC 6.0 ± 3.3*** 1.0 ± 0.3*** STm cheA 76.2 ± 33.5 40.8 ± 10.9** STm cheB 15.6 ± 2.7*** 1.2 ± 1.3*** STm fliC/fljB 12.5 ± 1.9*** 0.4 ± 0.3*** a: Performance of mutant strains was compared statistically to the wild type strain of the same serovar. **: p<0.01; ***: p<0.001. The inoculum of each strain was between Log10 7.9 and Log10 8.2 with no significant difference between

strains. Uptake and survival inside macrophages Once Salmonella has invaded the host, professional phagocytic cells Protein Tyrosine Kinase inhibitor quickly take up the bacteria. Especially the uptake by macrophages has been SYN-117 in vitro considered important, deduced from the fact that all S. Typhimurium mutants that are attenuated for macrophage survival have turned out to be non-virulent in challenge experiments [18]. To investigate whether macrophage interaction depended on the presence of flagella and chemotaxis genes, we conducted experiments with cultured J774A.1 cells. The results are shown in Table 2. S. Dublin strains with mutation in cheA, cheB and fliC were taken up by macrophages

in significantly lower numbers than the wild type strain. The mutants of S. Typhimurium were found to have the same general uptake phenotypes, however, the differences between the wild type strain and the cheA mutant were not significant. All strains increased in numbers from 3 to 24 hours, but due to relatively large standard deviations, only the difference in net growth of the S. Typhimurium fliC/fljB mutant JPH203 cell line was statistically different from that of the wild type strain. At 48 hours, wild

type and chemotaxis mutants decreased in numbers, however, the cheB mutant of S. Typhimurium was significantly less reduced compared to the wild type strain. Contrary to this, flagella-less mutants of both serotypes showed net growth, but only the S. Typhimurium strains was significantly different from the wild type strains. Table 2 Uptake and survival of S. Dublin 3246 (SDu) and S. Typhimurium (STm) wildtype and flagella and chemotaxis mutants in cultured J774A.1 macrophages a Strain Uptake 3h (Percent of wild type strain) Survival 24 h (Percent of same strain at 3h) Survival 48 h (Percent of same strain however at 3 h) SDu WT 100 124,1 ± 43.5 20.7 ± 4.7 SDu cheA 53.9 ± 15.1** 279.8 ± 65.8 53.8 ± 16.5 SDu cheB 1.4 ± 1.0** 307.7 ± 90.2 248.8 ± 39.8 SDu flic 1.0 ± 0.2*** 450.5 ± 255.0 615.3 ± 325.8 STm WT 100 114.0 ± 42.6 2.8 ± 1.72.8 STm cheA 72.4 ± 22.4 100.2 ± 31.0 12.2. ± 3.1 STm cheB 19.0 ± 9.3** 309.8 ± 231.5 81.7 ± 6.9* STm fliC/flijB 0.2 ± 0.1*** 490.9 ± 111.6* 702.9 ± 53.0*** a: Uptake of mutant strains was expressed relatively to and compared statistically to the wild type strain of the same serovar. Survival at 24 and 48 hours was expressed relatively to the number of bacteria determined at 3 hours and compared statistically to the survival capability of the wild type strain of the same serotype.