COMPARATIVE STUDIES ON SALMONELLA TYPHI GROWN IN VIVO AND IN VITRO. III. THE IMMUNIZING POTENCIES OF ACETONE-KILLED VACCINES PREPARED FROM IN VIVO- AND IN VITRO-GROWN BACTERIA AND THE IMMUNIZING POTENCY OF SUBSTANCES ISOLATED FROM INFECTED ORGANS.

Abstract

1. Salmonella typhi, strain Ty2, grown in vivo and employed as acetone-dried vaccine possessed a higher immunizing potency than the descendants of the same parent strain grown in vitro and employed as vaccine.2. When 2 × 108in vitro-grown bacteria were employed as challenge, the immunizing effects of both types of vaccine were more marked than after administration of 2 × 108in vivo-grown bacteria as challenge.3. The higher potency of the in vivo-grown vaccine was apparent in all experiments, whether the challenge strain was grown in vivo or in vitro.4. Immunogenic substances were isolated from infected organs of mice and guinea-pigs, and an immunogenic substance from the peritoneal fluid of the infected guinea-pigs was concentrated by precipitation with ethanol.