The bactericidal action of rabbit bile on certain strains of streptococci

The phenomenon here described was noted during the course of a series of experiments on rabbits designed to test the pathogenicity of a certain strain of hemolytic streptococcus. It was found that, although at autopsy the various organs of the peritoneal cavity were filled with living streptococci, the bile was always sterile. This led to the testing, in vitro, of bile from other rabbits as well as from various other animals, to find out, whether they possessed bactericidal action on this strain of streptococcus. All samples of rabbit bile proved to be bactericidal, whereas the bile of the ox, sheep, cat, dog, pig, guinea pig, and human exerted no deleterious effect on the streptococci.

The strain of streptoccus used (Strain “H”) 1 in these preliminary experiments was, according to Holman's classification, Streptococcus pyogenes—a hemolytic, non-mannite fermenting streptococcus. Our next step was to test various strains of streptococci from human and animal sources, these strains having been classified according to their hemolytic and sugar fermenting properties.

The results may be briefly summarized, by dividing the organisms into three groups, at least two of which are apparently clear cut.

I. All those hemolytic non-mannite fermenting Streptococci which fall, by Holman's classification, into the Streptococcus pyogenes group, were killed by rabbit bile, 1/50 of I C.C. of bile, or less being sufficient to kill 0.1 C.C. of a 24-hr. serum broth culture. Abmt twenty cultures of this type were tested.

11. All non-hemolytic Streptococci, whether of human or bovine origin, were unaffected by rabbit bile.

111. Hemolytic, mannite fermenting streptococci are almost always unaffected by rabbit bile. In a group of thirty or more of such strains tested, only two were killed by bile.

Since this bactericidal power of rabbit bile is undiminished by sterilization, attempts were made, by fractioning the bile, to determine, if possible, what constituent of rabbit bile is responsible for this highly selective bactericidal action.