An Example of Bacterial Synergism on Endo Medium.

Abstract

Bacterial Synergism has usually been studied in fluid medium. I wish to report here an example of the association of B. welchii and B. faecadis alkaligenes on an Endo plate with a resulting change of the type of colony formed by the latter. A swab taken from the drainage wound of an acutely infected shoulder, was planted in hormone-dextrose-broth and on blood agar. The broth showed a growth of gram negative bacilli and gram positive cocci in chains. The blood agar showed haemolytic colonies of streptococci and colonies of the coliform type. The broth culture was spread on an Endo plate and after 24 hours incubation this plate showed numerous colonies with red centers and narrow, colorless peripheries. In such isolations only colorless colonies are usually picked for further study, but because of the colorless periphery of these colonies, one was transferred to hormone broth. A smear from a 24 hour growth of this culture showed nothing but gram negative bacilli. Generous portions of the broth culture were ...