RESISTANCE OF BRUCELLA-ABORTUS INFECTED MICE TO INTRAVENOUS OR INTRAPERITONEAL BRUCELLA REINFECTION

  • 1 January 1976
    • journal article
    • research article
    • Vol. C127  (1) , 57-70
Abstract
The development of acquired resistance to B. abortus was studied in mice infected i.v. with small numbers of live CO2 dependent B. abortus 544 used as a vaccinal strain. CO2 independent B. abortus was used as a challenge strain. The influence of several parameters in the development of acquired resistance were examined. These were vaccination-challenge interval, challenge route, dose of challenge and challenge-sacrifice interval. The behavior of the challenge strain in normal mice depended on the size of the inoculum. After an i.v. inoculum of about 1 .times. 106 bacteria, the level of infection in the liver or the spleen followed 3 phases, a phase of increase of the viable counts, a phase of decrease and a phase of plateau. The decreasing phase was more pronounced in liver than in spleen. After an i.p. injection of the same dose of bacteria, an infection developed following approximately the same pattern, except during the 1st day of infection. One month after vaccination of an inoculum of about 1 .times. 104 viable B. abortus, an accelerated appearance of the decreasing phase almost completely prevented the multiplication of an i.v. challenge of about 1 .times. 106 B. abortus in the spleens. In the livers, the same phenomenon took place after a small increase of the bacterial population. After an i.p. challenge, the numbers of Brucella isolated from the spleens and livers of vaccinated mice 1st fell sharply to practically nothing around the 6th day, and then rose to reach a phase of slow increase or of plateau until the 24th day. The vaccinated population remained undisturbed by the reinfecting inoculum.

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