A neonatal mouse model of meningococcal disease.

Neisseria meningitidis, the meningococcus, remains a major cause of bacterial meningitis. Previously developed animal models for this infection do not adequately mimic its natural pathogenesis in humans. We have investigated a number of different potential animal models and describe a neonatal mouse model. Meningococci were instilled intranasally into five-day-old mice; invasiveness was measured by blood cultures and cisternal puncture, and colonization was determined by nasal cultures. Fifty two percent of mice became bacteremic after instillation of strains which are virulent for humans. Human carrier strains were avirulent in this model. Iron dextran enhanced the nasal colonization, invasiveness and mortality due to disease-associated isolates but had no effect on carrier strains. Colonization rates were similar for all strains. There was a marked age-related change in susceptibility to infection which was inversely correlated with levels of serums C3. Immunization of Swiss CD1 dams with N. meningitidis serotype 2 vaccine protected their litters from meningococcal infection. Protective levels of serum antibody were acquired by neonatal mice after suckling immunized dams. The neonatal mouse meets most of the criteria for an appropriate animal model for meningococcemia.