In chickens infected with the wild-type

see more strain, heterophil infiltration dropped between day 5 and day 12 and heterophil infiltration induced by the wild type strain on day 12 was similar to that induced by the ΔSPI1 mutant (Fig. 3). Figure 3 Heterophil infiltration in caeca of chickens infected with different SPI mutants of S . Enteritidis. Y axis, average number of heterophils per microscopic view ± SD. a, b, c – ANOVA test different at p < 0.05 in comparison to the group infected with the wild-type S. Enteritidis (a), the ΔSPI1-5 mutant (b), or the non-infected controls (c). Abbreviations: as in Fig. 1. Proinflammatory cytokine response Previous experiments had shown that the early heterophil infiltration decreased

with the loss of SPI-1. We therefore tested cytokine EPZ004777 in vitro signalling in the caeca of chickens infected with the ΔSPI1, ΔSPI2 and ΔSPI1&2 mutants. For all the cytokines measured, an identical CRT0066101 manufacturer trend was observed – the highest induction was observed in chickens after infection with the wild type strain, followed by those infected with ΔSPI2, ΔSPI1 and ΔSPI1&2 mutants, respectively (data not shown). Except for IL-12β, the expression of the remaining cytokines after infection with the wild-type strain and the ΔSPI2 mutant significantly differed from the expression observed in non-infected control chickens while the differences between the non-infected chickens and those infected with the ΔSPI1 and

ΔSPI1&2 mutant were always insignificant. Molecular motor Discussion In this study we were interested in the role of five major pathogeniCity islands in the virulence of S. Enteritidis for chickens. Rather unexpectedly, none of the pathogeniCity islands was essential for colonisation of the intestinal tract despite the fact that other studies demonstrated that single gene SPI-1 mutants in chickens or SPI-4 mutants in cattle showed impaired intestinal colonisation and/or mucosa invasion [13, 18]. We cannot exclude the possibility that, if the infectious dose was changed or the duration of animal infection was extended for a longer period of time, we would observe a correlation between the persistence in the gut and the presence of a particular SPI. It is also possible that the differences between a single gene mutant and the whole SPI-1 mutant are biologically relevant because in mice a difference in the behaviour of the whole SPI-1 mutant and a hilA mutant was observed. This difference has been explained by the presence of the SPI-1 localised genes stimulating the host’s immune response, the effect of which is suppressed in the presence of intact hilA [8].