ABSTRACT
The enterobacterial common antigen (ECA) is a polysaccharide composed of polysaccharide repeats that are located in the outer membrane of almost all Enterobacteriaceae bacteria and has diverse biological functions. ECA is synthesized by the synergistic action of multiple genes that are present in clusters on the genome of Enterobacteriaceae bacteria, forming the ECA antigen gene cluster, an important virulence factor that plays a role in host invasion and survival of Enterobacteriaceae in vivo. ECA also plays an important role in the maintenance of the bacterial outer membrane permeability barrier, flagella gene expression, swarming motility, and bile salts resistance. In addition, ECALPS, anchored in the core region of bacterial lipopolysaccharide, is an important surface antigen for bacteria, stimulating high levels of antibody production in the host and could be a target for vaccine research. This review summarizes ECA purification, genes involved in ECA biosynthesis, its immunological characteristics, biological functions and clinical applications.