Replication conditional plasmid and its use in the molecular genetic construction of vaccine strains of pasteurellaceae that contain temperature conditional replication of H. somnus, P. multocida and P. haemolytica

摘要

Replication-conditional plasmids which are useful for the Pasteurellaceae have been isolated and characterised. The plasmids can be utilized for delivery of DNA segments into the Pasteurellaceae in situations where control of extrachromosomal replication desired, such as in achieving allelic exchange or site-directed mutagenesis. A restriction endonuclease, HsoI, was isolated from a bovine lung isolate of Haemophilus somnus. The enzyme was found to be a true isoschizomer of HinPI, a commercially available enzyme originally isolated from Haemophilus influenzae PI. Commercially available HhaI methyl transferase was found to protect against cleavage by both enzymes. Methylation of foreign plasmid DNA was found to enhance transformation of Haemophilus somnus in excess of four orders of magnitude. The replication-conditional plasmid is useful for the production of live, attenuated vaccine production against respiratory disease syndrome in domestic cattle caused by Pasteurella haemolytica, Pasteurella multocida and Haemophilus somnus.