Neisseria meningitidis infection in mice: influence of iron, variations in virulence among strains, and pathology.

The influence of iron on Neisseria meningitidis infection in C-57 mice was examined. Iron sulfate, ferric ammonium citrate, and iron sorbitol citrate all proved to be too toxic for use as infection-enhancing agents. Iron dextran displayed an extremely low toxicity, enhanced infection in a dose-dependent manner, and resulted in infection enhancement factors approaching 10(9) for virulent strains of N. meningitidis. Fatal iron dextran-enhanced infection was shown to be reversible by in vivo chelation of iron. Virulent strains of N. meningitidis produced symptoms of infection and pathological lesions in mice both with and without iron pretreatment, but an avirulent strain failed to produce symptoms of infection or pathological lesions, regardless of iron administration. Iron dextran-enhanced infection in mice proved to be a useful model for the examination of virulence of various N. meningitidis strains. All of 9 isolates from clinical disease possessed virulence, whereas only 3 of 10 isolates from carriers possessed virulence, when examined by using this model.