Mean and median (with range) histopathology scores in spleen, liver and ileum of two-week old chickens experimentally infected with S. Typhimurium D23580 (ST313) or 4/74 (ST19).

Scores based on blind assessment based on pathology score outlined in Table 1 conducted by two individuals. Statistical comparison was made between the two infected groups using Mann Whitney U-test and indicates significantly greater pathology in the spleen and liver (P = 0.016) in the D23580 infected group at 3 days post infection and liver and 7 days post infection (P = 0.032) consistent with systemic salmonellosis associated with an invasive phenotype. Both isolates elicit a moderate inflammatory response in the ileum at 3 days post infection, albeit slightly greater in the 4/74-infected birds. At 7 days post infection this has largely resolved in D23580-infected birds but remains significantly higher in 4/74 infected birds (P = 0.014). n = 5 for each group per time point.