Studies on Colicin Production by Shigella sonnei

Since Abbott and Shannon introduced a systematic colicin typing of Shigella sonnei their method have widely been used for epidemiological studies of group D Shigellosis. However, the inhibition pattern based on their qualitative determination somewhat lacks in reproducibility.As the first step to improve the colicin typing of Shigella sonnei, attempts were made to establish a quantitative method for the determination of colicin activity and then examine basic conditions for the colicin production quantitatively. Types 5, 11, and 12 strains were used throughout the experiment. Both liquid and solid media were employed.The following results were obtained.1. Dorset egg medium was superior to cooked meat medium for the storage of colicin-producing strains.2. Colicin production was better at 37°C than at 30°C, although the difference in bacterial growth was little between the two temperatures of incubation.3. Similar to Escherichia coli which produces K and V colicins, yeast extract or cattle blood increased the colicin production by Shigella sonnei. Hence brain heart infusion (Difco) supplemented with 5% cattle blood was a medium suitable for the colicin production.4. Basic conditions for the colicin production on the solid medium were similar to those in the liquid medium, except that the colicin activity of type 12 strain began to decline at 48 hours of cultivation.