The Nature of the Reaction of the Colon Organism on Endo's Medium

Abstract

Bacterium coli was grown in a medium of a composition similar to Endo's medium with the exception that the sulfite, fuchsin and agar were left out. When the fuchsin-sulfite mixture was added after 24, 36 and 48 hours, or after 3 and 10 days of incubation at 37°C., no reaction appeared. The substance that causes the reaction is only formed when the bacteria are grown in the presence of sulfite. When picric acid and ether are added to the red compound produced by the colon organism in Endo's medium and the mixture shaken, the color remains in the watery layer and thus the dye color that appears in the medium is not restored fuchsin, but a new substance. The work confirms Neuberg's and Nord's theory that the Endo medium acts as a trapping agent for the intermediate product, acetaldehyde, which causes the Endo reaction.