Bacterial Vaccines:
Bacterial vaccines are composed of attenuated versions of the pathogen; that is, they are alive but reduced in virulence.
Attenuation may be accomplished in a number of ways:
- selection of a naturally occurring attenuated strain,
- repeated passage on artificial media, or
- elimination of a virulence trait by mutation of the gene encoding the trait.
The major advantages of bacterial vaccines are directly related to their being alive. Live vaccines not only have longer half-lives than their dead counterparts (regardless of location) but they will also express epitopes that may only be expressed in vivo, thus eliciting antibodies to epitopes that the pathogen will also express following infection. Another advantage is that live vaccines will elicit antibody and cellular immunity. A major disadvantage is that live vaccines may produce disease, for example, through reversion to the virulent phenotype. Also, if the vaccinated host has reduced resistance or if used in alternative host species, then the vaccine may produce disease.
Veterinary Bacterial Vaccines
- Anthrax spore vaccine (Sterne strain of B.anthracis suspended in glycerin and adjuvanted with saponin),
- BQ vaccine (Alum precipitated and formalin inactivated Cl. Chauvoei),
- HS vaccine (Alum precipitated and formalin inactivated Pasteurella multocida),