Construction and vaccine potential of an aroA mutant of Pasteurella haemolytica

The aroA gene, encoding 5-enolpyruvylshikimate 3-phosphate synthase, from Pasteurella haemolytica biotype A, serotype 1 was cloned by complementation of the aroA mutation in Escherichia coli strain AB2829 after electroporation with a DNA library constructed in pUC18. The cloned P. haemolytica aroA gene was inactivated by insertion of a kanamycin resistance gene and reintroduced by allelic exchange into the chromosome of the parental P. haemolytica using PbluescriptII SK+. The P. haemolytica aroA mutant was highly attenuated in a mouse septicaemic model. Mice immunized intraperitoneally with two doses of live P. haemolytica aroA mutant were protected against a lethal parental strain challenge.