A method for the isolation of toxic and immunizing fractions from bacteria of the Salmonella group

Abstract

Dried killed cells of Bact. typhi-murium and Bact. typhosum (strains R.R. and Ty2) were extracted at 38[degree] with aqueous urea solns. of 2.5[image] or 6.5[image] conc. After removal of bacterial debris in a continuous centrifuge, the urea was removed by dialysis and the dialysed solns. were filtered through bacterial filters. The filtered solns. were concentrated, acidified slightly with acetic acid and treated with alcohol to a conc. of 68% by wt.; about 2-4% of the wt. of the bacterial bodies used was recovered in the form of a carbohydrate-containing, possibly protein-free, amorphous solid. Lengthy extraction yielded fractions with much reduced activity. The most toxic fractions from Bact. typhi-murium had an A.L.D. of approx. 0.2 mg., the most toxic Bact. typhosum prepns. had an A.L.D. of approx. 0.4 mg., for mice. 2 prepns. were tested for immunizing potency with positive results.