Enteroaggregative Escherichia coli (EAEC)

A cause of diarrhea worldwide, enteroaggregative Escherichia coli (or EAEC) is one of six diarrheagenic E. coli pathotypes. EAEC strains are heterogeneic in terms of virulence factors, adhere strongly to epithelial cells, and produce a strong biofilm. It is the characteristic aggregative adherence on epithelial cells that was both the gold standard of clinical identification and the source of the appellation “aggregative.” To understand EAEC in the continuum with other pathogenic E. coli, we discuss the overlap of EAEC with other diarrheagenic E. coli and extraintestinal pathogenic E. coli isolates. Due to the increased use of molecular techniques for the identification of EAEC, the use of various PCR markers and DNA sequencing for EAEC identification and how that correlates to the phenotypic definition is discussed. Aspects of EAEC pathogenesis, including an overview of virulence factors, such as the five aggregative adherence fimbriae (AAF) and SPATEs (serine protease autotransporters of Enterobacteriaceae), will be explored. The advantages and limitations of various EAEC animal models and what is known about human immunity and host factors that influence infection outcomes are outlined. This review includes a synthesis of new discoveries published for the EAEC field, including non-AAF fimbrial adhesins, additional information about post-infection sequelae, and new EAEC models.