The preparation of ethanol extracts from rabbit serum, egg yolk and bovine heart excludes proteins as essential growth-promoting factors for Leptospira canicola. Since solutions deproteinated in precipitation tests with trichloroacetic acid and ammonium sulfate are ineffectual, in contrast to protein fractions, it is possible that the unknown substances settle out with the protein. The weak activity of heated media presumably is based on a similar effect. During treatment with ethanol, the growth-promoting substances at least go into partial solution. They are thermostable at 100C and 15 minutes activity. Longer durations and higher temperatures were not tested. As evident from dilutions made during preparation of egg yolk extract, leptospirae become motionless after a few hours in a concentrated solution. Reproduction appears only in greater dilutions. It is not clear whether the unknown substances are inhibitory in greater amounts or whether entirely different substances, whose activity ceases upon dilution, have this effect.
Trans. of Zentralblatt fuer Bakteriologie, Parasitenkunde und Infektionskrankheiten. Abt. 1. Originale (West Germany), v162, p106-111, 1955.