Abstract: Objective To investigate the degrees of injury severity of sepsis models made by different kinds of Escherichia coli. Methods The 152 mice were randomly divided into control group, DH5α group, 44102 group, and 25922 group, with 38 rats in each group. DH5α group, 44102 group and 25922 group were intraperitoneally injected with 300 μL of Escherichia coli DH5α, 44102 and 25922 at the concentration of 1.0 × 109 CFU/kg to prepare sepsis models of different kinds of Escherichia coli. Control group was injected intraperitoneally with the same amount of normal saline. (1) After 8 h,four mice were taken from each group for peripheral blood bacterial culture . (2) After 12 h, ten mice in each group were used for measuring serum levels of TNF-α and IL-6 by enzyme-linked immunosorbent assay (ELISA). (3) Western blot assay was used to determine the serum levels of high-mobility group protein (HMGB1) in four mice of each group. (4) Ten mice in each group were used to measure serum levels of alanine transaminase (ALT), aspartate aminotransferase (AST), creatinine (CR) and blood urea nitrogen (BUN) by automatic biochemical analyzer. (5) After liver, lung and kidney tissues were fixed with formaldehyde, hematoxylin-eosin (HE) staining was performed (n=10 for each group). Results In DH5α group, 44102 group and 25922 group, bacteria, inflammatory cytokines TNF- α, IL-6 and HMGB1 protein, liver and kidney indicators ALT, AST, CR and BUN showed a sequential increasing trend (P＜0.01). The severe degrees of alveolar structure damage,hepatic cell infiltration and renal glomerular atrophy were DH5α group, 44102 group and 25922 group in turn. There were no obvious damages of lung, liver or kidney tissues in control group. Conclusion Escherichia coli 25922 induces severe sepsis injury and can be used to study the animal models of the initial inflammatory phase of sepsis. Escherichia coli 44102 induces moderate damage of sepsis and can be used in animal models that do not require definitive sepsis staging experiments. Escherichia coli DH5α induces less damage of sepsis and can be used to explore immunosuppressive therapy of the animal model of sepsis.

Key words: sepsis, systemic inflammatory response syndrome, disease models, animal, Escherichia coli, tumor necrosis factor-alpha, interleukin-6