ECA - Wspólny antygen powierzchniowy pałeczek rodziny Enterobacteriaceae

Abstract

Almost all the strains of bacteria belonging to the Enterobacteriaceae family share at least one common antigenic component, ECA, which is not present in other Gram-negative and Gram-positive bacteria. From the observations made with immunofluorescence and immunoferritin techniques, it has been concluded that ECA is localized in the outer leaflet of the outer membrane of Gram-negative enteric bacteria. ECA is a glycolipid consisting of linear trisaccharide repeating units composed of [→3)-α-D-Fucp4NAc-(1→4)-β-D-ManpNAcA-(1→4)-α-D-GlcpNAc-(1→]. It occurs in three structural forms: ECAPG linked to phosphatidylglycerol, ECALPS anchored to LPS core region and ECACYC not expressed on the surface. ECA is believed to be connected to the LPS outer core. However, it should be emphasized that Yersinia enterocolitica serotype O:3 mutants defective in outer core synthesis were also ECA-immunogenic. The genes involved in ECA biosynthesis are located in the chromosomal wec gene cluster, from wecA to wecG and the ECA expressions is downregulated at host temperature. So far, ECA has been thoroughly analyzed at the structural and genetic level, however, its significance in vivo has been investigated in relatively few studies. ECA has been linked to pathogenesis in several species of bacteria, although this function seems to differ between the species. ECA has been shown to be involved in the flagellar assembly and motility in Serratia marcescens Also, the ECA-negative mutants of Salmonella enterica serovar Typhimurium proved to be significantly less virulent than the parental strain. ECA as a marker of Enterobacteriaceae family is a valuable indicator of water and food contaminations with enteric bacteria.