Early systemic inflammatory response in mice after a single oral gavage with live Escherichia coli is evidenced by increased TNF-alpha and nitric oxide production

Twenty-four female BALB/c mice were orally inoculated with 10 ⁸ CFU Escherichia coli ATCC 25922 and euthanized 2.5, 7, 13 and 25h post-inoculation. The levels of organ nitric oxide (NO) and plasma endotoxin, TNF-alpha and nitrite/nitrate (NO _x) were compared to those found in sham-inoculated mice, to evaluate systemic host-response to a low-level oral exposure to Gram-negative bacteria. Organ bacterial culture and immunohistochemistry for iNOS were performed on lungs, liver, kidneys and brain from all mice. Organ NO and plasma TNF-alpha levels were higher in E. coli-inoculated animals, but no differences were detected in plasma endotoxin levels, NO _x or iNOS immunostaining for any of the animal groups. Single oral gavage with live E. coli stimulates an early systemic immune response in clinically healthy mice as evidenced by increased plasma TNF-alpha and organ NO levels, but bacteremia and endotoxemia are not related to this inflammatory response.