Table 1.
Histopathology scoring system for experimental avian salmonellosis.
Figure 1.
Viable counts of Salmonella Typhimurium ST313 and ST19 in cecal contents and spleen following oral infection of the chicken.
Viable counts (CFU/g) of cecal content (A) and spleen (B) at 3 and 7 days post-oral infection of two week old commercial egg laying chicks with 108 CFU ST313 (D23580, Q456) and ST19 (F98, 4/74) S. Typhimurium. Counts are shown as individual birds with the bar representing the median value. Five birds from each group were killed for sampling at each time point (n = 5) in each experiment. Data shown for D23580 and 4/74 (n = 10 per time point) is combined data for two separately repeated experiments. Statistical comparison was made using a Kruskal-Wallis test. *, P<0.05. **, P<0.01. ***, P<0.001.
Figure 2.
Expression of CXCL chemokines in the chicken gastrointestinal tract following infection with S. Typhimurium ST313 or ST19.
Expression of the chemokines CXCLi1 and CXCLi2, considered to be orthologous to mammalian IL-8, were determined by qRT-PCR. Relative expression in ceca (Figure 2A) and ileum (Figure 2B) of ST313 (D23580) and ST19 (4/74) infected groups were made in comparison to mock-infected control birds by (2−[ΔΔCT]) method. Data is expressed as fold changes in expression in individual birds with the bar representing the mean value. Expression was determined in five birds per group at each time point. Statistical comparison was made by ANOVA. *, P<0.05. **, P<0.01.
Figure 3.
Histopathological changes in the ileum following infection with S. Typhimurium ST313 or ST19.
Photomicrographs (×400 magnification) of histological changes in H and E stained fixed ileal tissue following infection with S. Typhimurium ST313 show a rapid inflammation at three days post-infection leading to villus fusion and flattening accompanied by infiltration of lymphocytes and polymorphonucelar cells (heterophils) and crypt hyperplasia. By seven days post-infection, inflammation and pathology is reduced. In birds infected with ST19 (4/74) S. Typhimurium the inflammatory process appears slower with limited inflammation at three days post infection, but substantial damage to the structure of the ileum at seven days post-infection with a high degree of villus damage and large areas of inflammatory infiltration. Arrows indicate heterophil influxes. Scale bar = 100 µm.
Table 2.
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).
Figure 4.
Histopathological changes in liver and spleen following infection with S. Typhimurium ST313 or ST19.
Photomicrographs (×400 magnification) of histological changes in H and E in fixed splenic and liver sections at seven days post infection. Both ST313 (D23580) and ST19 (4/74) infection result in hepatosplenomegaly as shown by the influx of inflammatory cells, and this is greater in ST313 infection. Infection also results in granuloma-like lesions typical of avian salmonellosis, which are larger and more numerous in the ST313 infected birds. Black arrows indicate granuloma-like lesions and white arrows indicate heterophil influxes. Scale bar = 100 µm.