Control of Salmonella Infections in Mice by Streptomycin

Abstract

Preliminary observations on the use of streptomycin to control paratyphoid infections in mice indicated that this antibiotic given orally may be an effective means of eliminating Salmonella infections in colonies of mice and other laboratory animals for considerable periods of time. This paper reports the results of work∗ started in November 1945 when it was found that Salmonella organisms were responsible for both decreased production of mice needed for the Japanese B encephalitis vaccine program and also were the cause of contamination of the final vaccinal product.

A commercial mouse colony which was supplying mice for the Japanese B program was selected for streptomycin feeding since mouse brain vaccine prepared from these mice contained Salmonella organisms. Individual fecal samples were collected from the 1400 breeders in the colony, and streaked on brilliant green agar. Of this number, 30 adult mice in 6 breeding units yielded positive cultures (Salmonella enteritidis). Streptomycin† was incorporated in the drinking water of the entire colony for 7 consecutive days so that the daily intake per mouse was approximately 100 units. Two weeks later 100 young mice were used from the same 6 Salmonella positive units for vaccine production. No paratyphoid organisms were found in the vaccine produced from this group. The 30 positive adult mice and 24 of their offspring were tested 4 weeks after the streptomycin was fed and at monthly intervals thereafter. Only one adult mouse yielded a positive fecal culture in the first test, and all 4 subsequent tests on both young F, and old mice were negative for the presence of paratyphoid organisms.

As a further development of these findings experiments are now in progress to study the effect of 23, 50, 100, 200, 400 and 1000 units of streptomycin daily on the spread of S. enteritidis infection in groups of mice consiting of infected and non-infected individuals.