Evaluation of the efficacy of
vaccine candidates that prevent enteropathogenic and enterohemorrhagic Escherichia coli (EPEC/EHEC)
infection in mouse models is difficult due to their limited pathogenicity in mice. Citrobacter rodentium, a murine pathogenic bacterium that shares its
infection strategy and virulence genes with EPEC/EHEC, has been used as a model pathogen to develop novel
vaccine strategies or platforms for these bacteria. However, there are few reports on the comparative effectiveness of novel
vaccine platforms as no C. rodentium
vaccines have yet been prepared by standard methods such as bacteria attenuation or inactivation. In this study, we investigated the protective effect of the
oral administration of
formalin-inactivated C. rodentium (Fo-CR) on C. rodentium
infection in two mouse strains, C57BL/6 and C3H/HeN, as these strains have different degrees of susceptibility to
infection. In C57BL/6 mice, administration of Fo-CR induced significant C. rodentium-specific mucosal and systemic antibody responses, promoted bacterial clearance from the gut and inhibited colonic
hyperplasia. Furthermore, in C3H/HeN mice, the administration followed by lethal C. rodentium
infection induced significantly high avidity serum
IgG specific to C. rodentium and inhibited death,
body weight loss, and bacterial invasion to visceral organs. In conclusion, the
oral administration of Fo-CR resulted in the protection of mice from C. rodentium
infection, indicating that it serves as a reference method for evaluating the efficacy of novel oral
vaccine candidates or platforms.