Immune response of pigs to Salmonella enterica serovar Derby and Typhimurium infections.

Interaction between pigs and Salmonella enterica serovar Derby (Salmonella Derby) is much less understood in comparison with Salmonella enterica serovar Typhimurium (Salmonella Typhimurium). To study interactions of weaned piglets with Salmonella Derby, we compared the course of infections with Salmonella Derby De1 and Salmonella Typhimurium DT104 strains, both isolated from pig herds with a long history of asymptomatic infection. Salmonella Derby strain used was shed during the 28-day experiment period, while Salmonella Typhimurium strain was not found in faeces after day 17 post-infection. When the piglets were co-infected with both strains, Salmonella Derby was present in faeces until the end of the experiment, whilst Salmonella Typhimurium disappeared after day 21 post-infection. At the end of the experiment, Salmonella Derby was present in more tissues when compared with Salmonella Typhimurium. Piglets infected with Salmonella Typhimurium responded earlier with synthesis of anti-lipopolysaccharide IgM and IgG antibodies and with higher antibody levels compared to piglets infected with Salmonella Derby. Cellular immune response to both strains was very low and was detected later than was the onset of IgG antibody production.