Pathogenic Escherichia coli – virulence mechanisms

Abstract

E. coli are the predominant microorganisms in the human gastrointestinal tract. In most cases, they exist as harmless comensals, and some of them are beneficial to their host in balancing gut flora and absorption of nutrients. However, there are pathogenic strains that cause a broad range of diseases in humans and animals, from diarrhea to bloodstream infections. Among bacterial strains causing these symptoms, seven pathotypes are now recognized: enteropathogenic E. coli (EPEC), shiga toxin-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAEC), diffusely adherent E. coli (DAEC), and adherent-invasive E. coli (AIEC). Several different strains cause diverse diseases by means of virulence factors that facilitate their interactions with the host, including colonization of the intestinal epithelial surfaces, crossing of the mucosal barriers, invasion of the bloodstream and internal organs or producing toxins that affect various cellular processes. Pathogenic E. coli are commonly studied in humans, animals, food and the environment, in developed and developing countries. The presented paper reviews recent information concerning the pathogenic mechanisms of E. coli, the role of animals and food in the transmission chain and a short overview of epidemiological data.