Inflammatory and pathological changes in Escherichia coli infected mice

Purpose: Understanding the inflammation and histopathological changes in vivo caused by Escherichia coli infection is of great significance for scientific research and clinical diagnosis. Methods: Mice were randomly divided into 6 groups (N = 10) after adaptive feeding, and it challenged by intraperitoneal injection with different concentrations of E. coli ATCC25922. The survival situation within 7 days was recorded, and the half-lethal dose (LD50) was calculated by Karber's method. After the end, the blood, heart, liver, spleen, lung, and kidney of the mice were collected. We detected the concentration of inflammatory cytokines (IL-6, IL-beta, and TNF-alpha) and inducible nitric oxide synthase (iNOS) in serum by ELSIA. Organs were observed by histopathological staining and electron microscope observation. Results: The LD50 of mice infected with E. coli was 1.371*10(6) CFU/kg. The concentrations of IL-6, IL-beta, and TNF-alpha increased with time after infection in mice, reaching the highest concentration on the 7th day. iNOS was significantly increased on the 1st day of infection, and then decreased over time (P < 0.01). Within a week after infection, the colony counts of the heart, liver, spleen, lung and kidney showed a first decrease, and then reached a surge on the 7th day. Pathological results showed that a small amount of mitochondrial swelling and autophagy were seen in the spleen, lung and kidney tissues of the infected group; and a small amount of secondary lysosomes and autophagy were also seen; but no pathological changes were found in the liver and heart. Conclusion: Escherichia coli can cause inflammation and oxidative stress in mice, causing different degrees of damage to the spleen, lung, and kidney tissues, which provides theoretical support for inflammatory and pathological changes caused by Escherichia coli infection in vivo.