A vaccine comprising a bacterium that has an aroC/ompF/ompC combination mutation and optionally a mutation in a fourth gene

摘要

A bacterium attenuated by a non-reverting mutation in each of the aroC gene, the ompF gene and the ompC gene is described. The bacterium is useful as a vaccine. The bacterium may, for example, be an attenuated strain of E. coli useful in vaccination against diarrhoea.