An appreciable level of immunity from intraperitoneal infection with Pasteurella haemolytica was
established in mice by using a vaccine prepared in a conventional bacteriological culture medium, with aluminium
hydroxide gel as adjuvant. The level of immunity could not be elevated by using bacteria grown in tissue
culture media, enriched brain heart infusion broth, the addition of serum to the media or by using bacteria that
had been harvested in the logarithmic growth phase.
Although various extracts of the bacteria elicited a distinct immunity, the imrnunogenicity of vaccines
containing bacteria could not be enhanced by augmentation with those products.
The potential application of the vaccine in cattle and sheep is discussed.
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