EXPERIMENTAL SHIGELLA INFECTIONS IN MICE

I. AN ATTEMPT TO ESTABLISH INFECTION WITH THE AID OF ANTIBIOTICS AND RESISTANCE- LOWERING AGENTS

Abstract

A continuous oral administration of antibiotics, mostly chloramphenicol, in combination with resistance-lowering agents, such as carbon tetrachloride, cortisone acetate and croton oil, was very effective in establishing infections in ddN and CFW strains of mice when they were challenged with resistant strains of Shigella flexneri 2b and 3a.
The inoculated organisms remained in the intestinal tract for about a week in most of the animals and for as long as 4 or 5 weeks in a few.
Pathologic examination revealed that lesions developed in various organs, especially the intestinal tract, showing acute or chronic colitis.
Infection was not induced in animals which were inoculated with sensitive strains; because of the disruption in the administration of antibiotics to these animals, no organisms could be found in their feces within 1 or 2 days.
Thus, it is concluded that the elimination of intestinal microbial flora with the aid of antibiotics is of primary significance in establishing Shigella infection in mice, and that the resistance-lowering agents seem to play a secondary role in accelerating the infection.
Differences in the serotypes of Shigella flexneri (2b and 3a) and in the sexes (male and female) and strains (ddN and CFW) of the test animals did not seem to influence the grade or course of infections as far as the results obtained were concerned.