Thermolabile Toxin and Thermostable Tuberculin Components in Berkfeld Filtrates of Broth Cultures of Tubercle Bacilli.

In these experiments, normal and tuberculous guinea pigs were used to determine by intracutaneous tests whether or not Berkfeld filtrates prepared from broth cultures of tubercle bacilli contain toxins which might be distinguishable from tuberculin elements. One series of tuberculous animals had been infected 3 weeks prior to the test and showed early tuberculosis with little, if any, toxemia. The other group of animals, infected 4½ months previously, showed well marked signs of advanced tuberculosis.

A human strain of virulent tubercle bacilli was inoculated into ordinary infusion broth containing 5 per cent glycerine. The Berkfeld filtrates were prepared from a 26-day old culture grown at a temperature of 38° to 40° C. One lot of the nitrate was heated at a temperature of 63° to 65° C. on a water bath. Both portions were preserved with 0.25 ether tricresol. At the time the experiments were made, the material had been stored in the ice-chest for 4 days.

The animals were injected intracutaneously with 0.03 cc. of the heated and unheated filtrates, respectively, in a dilution of 1:2 (with physiological salt solution). Another series of experiments was set up with unheated filtrates combined separately with equal volumes of normal guinea pig serum and with serum from tuberculous guinea pigs, and incubated for one hour at 37° C. on a water bath before injection. The object of these experiments was to determine the effect, if any, which normal and tuberculous guinea pig serum might have upon the reacting properties of the filtrates. These combined materials were injected in 0.03 cc. amounts as in the preceding series and controlled with guinea pig serum alone.