Using defined mutants, we have investigated the contribution that five such loci play in the colonization of the avian reproductive tract, other organs and avian macrophages. All loci appear to play a small role in infection of liver and spleen, but not in colonization of the reproductive tract or macrophages. Infection with Salmonella enterica serovars is a major cause of human gastrointestinal tract disease with Salmonella Enteritidis (SEn), being by far the most common serovar

in the United States and European Union accounting Ruxolitinib for over 50% of cases (Patrick et al., 2004; ECDC, 2009). Consumption of infected eggs and egg products has been the most commonly identified route of infection (Braden, 2006). In the UK, the overall cost of infection with serovars Typhimurium and Enteritidis was recently estimated as £6.5 million per year (Santos et al., 2011). Egg contamination with Salmonella can occur both vertically (via invasion of the developing egg from infected reproductive tissues) and horizontally (via faecal contamination of the eggshell and subsequent penetration of bacteria). The relative importance of these two routes is still unclear (Gantois et al., 2009). The particular association of SEn with eggs suggests that this serotype has specific traits that facilitate interaction with the reproductive organs of layers and/or entry to and survival in the egg (Gantois

et al., 2009). Colonization of the reproductive tract by Salmonella is a multifactorial process, with cell membrane structure, fimbriae, flagellae, lipopolysaccharide and stress responses all playing GSK J4 clinical trial a role (reviewed in Gantois et al., 2009). Genome sequencing revealed genomic islands in SEn and the avian-adapted serovar Gallinarum that Benzatropine are not present in Typhimurium, the second most common serovar associated with human disease (Davidson,

2008; Thomson et al., 2008). These islands range in size from 6 to 45 kb and encode primarily hypothetical proteins of unknown function. Island genes with a putative function include cell-surface binding, metabolism, membrane transport, DNA binding, a type VI secretion system remnant, a Toll/interleukin-1 receptor family protein and an integrated phage carrying a type III secretion system effector. Genes in three of these islands have been shown to have a role in experimental infection of mice (Newman et al., 2006; Quiroz et al., 2011; Silva et al., 2012). While none of the islands were found to be exclusive to avian-adapted serovars, PCR screening showed that the majority of analysed SEn (18 of 25) and Gallinarum (7 of 7) isolates possessed all five islands (Davidson, 2008). We sought to determine whether these loci have a role in colonization of chickens, with a particular focus on the reproductive tract. SEn strain Thirsk, a phage type 4 poultry isolate, was originally from the Central Veterinary Laboratories, Weybridge, UK. The sequenced SEn P125109 (NCTC13349) (Thomson et al.