STUDIES ON IMMUNIZATION AGAINST PLAGUE VI

Abstract

A medium and cultural conditions were developed for opt. growth of Pasteurella pestis, strain A1122 (avirulent), for production of Fraction I and somatic antigen. Max. growth of P. peatis (4 to 5 x 109 organisms/ml.) occurs on the 3d day of incubation and is followed by massive cell lysis which ceases by the 6th day. At least 3 different components of the plague bacillus are released into the medium during the growth cycle: Fraction I, somatic antigen(s), and toxin. Fraction I is released continuously during the logarithmic phase of growth, and a max. concn. of about 1.0 to 1.4 mg./ml. of supernatant fluid is produced by the 3rd day. The somatic antigens are released during the lytic phase, reaching a max. at the conclusion of cell lysis. Toxin is released both during cell growth and during lysis. The antigen content of the casein hydrolysate mineral glucose supernatant is shown to be higher than that in other vaccines tested. Evidence points to the existence of Fraction I as the highly soluble gelatinous envelope surrounding the cells of P. pestis. The relationship between this substance, the Airies antigen, and the capsule of P. pestis is discussed.