Innate resistance of mice to experimental infection with Naegleria fowleri.

The mouse system provides an excellent model for studying host resistance to Naegleria fowleri, the agent of primary amoebic meningoencephalitis. Innate resistance to infection with N. fowleri was examined with respect to infecting dose and the age, sex, and strain of mice. Intravenous inoculation with 10(7) amoebae per mouse produced 100% mortality in 9 days, whereas inoculation with fewer amoebae reduced the cumulative mortality. Male and female DUB/ICR mice of varying ages were inoculated intravenously with 2.5 X 10(5) N. fowleri per g of body weight. The youngest mice died first, with 100% mortality for both males and females, and mortality decreased with increasing age. Female mice were significantly more resistant to infection than males. Five strains of mice weighing approximately 20 g were inoculated intravenously with weight-adjusted doses; mortality ranged from 10% in C57BL/6 mice to 95% in A/HeCr mice.