ABSTRACT
Shigella inhibition could be reversed either by aeration of the cultures or by the addition of glucose to the medium. When it was demonstrated that mice and guinea pigs could be infected with Salmonella, Shigella, and V. choierae after treatment of the animals with antibiotics, a convenient experimental animal became available for studies, in vivo, of enteric pathogen-normal flora interactions. Studies on the interactions between enteric pathogens and normal flora have dealt primarily with the function of the normal intestinal flora as a protective mechanism in preventing establishment of enteric infections.' Elimination of a portion of the normal flora lowered the ID50 of Salmonella from one million viable bacteria per mouse to fewer than 10 bacteria. Shigella population levels in the ceca of mice associated with Bifidobacterium and Streptococcus showed 10-fold and 100-fold reductions, respectively, as compared with Shigella populations in monoassociated mice.
