The IncP island in the genome of Brucella suis 1330 was acquired by site-specific integration.

An 18,228-bp region containing open reading frames predicted to be derived from the IncP plasmid or phage ancestors is present in the genomes of Brucella suis biovars 1 to 4, B. canis, B. neotomae, and strains isolated from marine mammals, but not in B. melitensis, B. abortus, B. ovis, and B. suis biovar 5. The presence of circular excision intermediates and the results of an analysis of sequenced bacterial genomes suggest that the region downstream of the guaA gene is a hotspot for site-specific integration of foreign DNA mediated by a CP4-like integrase.