Susceptibility to Salmonella typhimurium infection increases with age in C57BL/6 mice

Enterocolitis due to Salmonella infection is the most common cause of death from food borne illnesses in the U.S. Salmonella typhimurium (ST) is most frequently associated with this disease. ST infection can be particularly severe in the elderly. However, a well‐defined animal model to study the effect of age on ST‐induced enterocolitis, and its underlying mechanisms, has not been established. Young and old streptomycin‐pre‐treated C57BL/6 male mice were inoculated with high dose (3 ×10 8 colony forming units [cfu]) or low dose (5 ×10 5 cfu) of ST or PBS. ST counts were determined by cfu recovered from the gut contents of the ileum, cecum, and colon, and mesenteric lymph nodes, peyer's patches, liver, and spleen of mice at days 1, 2, and 4 post infection (pi). On day 2 pi, old low dose infected mice had significantly higher ST cfu than young low dose infected mice in the spleen (p<0.05). By day 4 pi, old infected mice had higher cfu than young infected mice in the ileum, colon, peyer's patches, and liver (p<0.01). Both young and old mice exhibited weight loss following the infection, however, old mice had significantly higher weight loss than young infected mice on days 1 and 2 pi (p<0.05). Thus, old mice exhibit significantly greater ST colonization of the ileum, colon, peyer's patches, and liver, and lost more weight compared to infected young mice. This animal model may be useful for future studies of the aged host response to ST‐induced enterocolitis. Support by USDA #58 1950 9 001.