Experimental Studies of Immunity in Pertussis
2. Mechanisms of the Intracerebral Infection with B. pertussis in mice
1962 Volume 17 Issue 12 Pages 932-937
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1962 Volume 17 Issue 12 Pages 932-937
Many workers reported on the experimental studies on pertussis by the intraperitoneal, intranasal or intracerebral routes of infection. Although the mice could be killed when they were injected intraperitoneally and intranasally with large amounts of B. pertussis, the death would be principally caused by the toxicity of the inocula itself and not infection. Therefore, the intracerebral infection in mice has been generally used in experimental studies of pertussis immunity and the protection test of pertussis vaccine.
In the present studies it was intended to examine the multiplication of B. pertussis (phase I: 18-323, variant:#33 and phase III: Sugata) inoculated intracerebrally and its relationship to the death of infected mice, and also the death of mice inoculated intracerebrally with various doses of killed organisms of five strains of B. pertussis /phase I: 18-323, Tohama; variant:# 33, # 29; phase III: Sugata. And the results obtained are as follows;
Mice inoculated intracerebrally with lethal doses of 18-323 and # 33 strains of B. pertussis showed a marked rise in the number of viable organisms in the brain at 5 to 7 days after infection. All mice die within 4 to 7 days after infection showing the microbial populations of 108 to 1010 viable units in the brain. The number of viable organisms in the brain of each mouse, which did not show any symptoms of meningitis or encephalytis, was under 10 viable units at 5 to 7 days after infection and thereafter a striking reduction of microbial populations was observed. On the other hand, mice inoculated with B. pertussis of phase III showed a remarkable decrease of viable organisms in the brain during the entire observation period and all mice survived.
The ability of killed B. pertussis of various phases was compared at doses of 107, 108 and 109 organisms. Death rate of each group of mice inoculated with 109 organisms of phase I and variant strains of B. pertussis was 80 to 100 per cent respectively, and 107 and 108 organisms of these strains killed no or only a few mice. Moreover, mice inoculated with 107, 108 and 109 organisms of phase III B. pertussis did not die within 72 hours after inoculation.
From the above mentioned findings, it will be concluded that the death of mice infected intracerebrally with lethal dose of virulent B. pertussis is due to the toxin produced in the brain as the result of the growth of organisms to the level of 108-109 viable units.
