Modifying effect of colicin on experimental Shigella keratoconjunctivitis.

The ability of colicinogenic bacteria and colicin to inhibit Shigella sonnei during the course of infection was studied. Infection of the guinea pig conjunctivae was used as the experimental model. In S. sonnei-infected guinea pig conjunctivae which were treated with a colicinogenic strain of Escherichia coli or with colicin, the number of S. sonnei cells was lower than in animals infected with S. sonnei but not treated. The decrease in the number of pathogenic organisms was associated with absence of disease. A noncolicinogenic strain of E. coli had no effect on production of disease in infected animals. Treatment with a colicinogenic strain of E. coli or colicin did not affect the production of disease or the numbers of organisms in an animal infected with a colicin-resistant strain of S. sonnei.