Pathogenicity and immunogenicity of native and mutant strains of Pasteurella multocida, the causative agents of haemorrhagic septicaemia

Document Type : Full paper (Original article)


1 Department of Microbiology, Faculty of Veterinary Medicine, University of Urmia, Urmia, Iran

2 Department of Aerobic Vaccine Production, Razi Vaccine and Serum Research Institute, Karadj, Iran

3 Department of Biotechnology, Razi Vaccine and Serum Research Institute, Karadj, Iran


Haemorrhagic septicaemia (HS) is a fatal systemic disease of cattle and buffaloes. Some control is
achieved with administration of alum-precipitated or oil-adjuvanted killed whole-cell vaccines injected
subcutaneously. These vaccines, however, provide only short-term immunity and for effective use, they
should be administered annually. We constructed an aroA attenuated derivative of a Pasteurella multocida
serotype B:2 strain by allelic exchange of the native aroA sequence with aroA sequences disrupted with a
kanamycin resistance cassette. This strain was confirmed to be aroA mutant by PCR. The aroA derivative
was highly attenuated for virulence in a mouse model of HS and rabbits. Mouse and rabbit challenge
experiments showed that i.p. or i.m. vaccination of an aroA strain completely protected mice or rabbits
against challenge with a high dose (>1000 LD50) of the parent strain.