Attenuated gram negative bacteria with nucleotide sequence mutations

摘要

Provided is a mutant of a Gram negative bacterium, wherein the bacterium has a mutation in a nucleotide sequence with sequence identity of more than 70% to a specified sequence from Pasteurella multocida, which codes for a polypeptide, and wherein the mutation attenuates virulence of the bacterium. Further provided are immunogenic compositions and vaccines comprising the mutant bacterium.