Campylobacter jejuni ST-403 cloncal complex characterisation

Campylobacter jejuni is a highly diverse species of bacteria commonly associated with infectious gastro-intestinal disease of humans and zoonotic carriage in poultry, cattle, pigs, and other animals. The species contains a large number of distinct clonal complexes which vary from host generalist lineages commonly found in poultry livestock and human disease cases, to host-adapted specialised lineages primarily associated with livestock or poultry. Here we present novel data on the ST-403 clonal complex of C. jejuni, a lineage showing association with porcine hosts. Our data shows this is a phylogenetically distinct lineage exhibiting a distinctive pattern of intra-lineage recombination which is accompanied by the presence of lineage specific restriction-modification systems. Furthermore we show that the ST-403 complex has undergone gene decay at a number of loci. Our data shows that host association of C. jejuni lineages can be connected with both gene gain and gene loss through pseudogenisation, potentially associated with niche adaptation of this most important human pathogen.