Enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (often referred to as EAEC) is a pathotype of Escherichia coli often associated with diarrhoeal illness. The defining characteristic of EAEC compared to other pathotypes of E. coli is a "stacked brick" pattern of adhesion to the human epithelial cell line HEp-2. The pathogenesis of EAEC involves the bacteria aggregating and colonizing the intestinal mucosa, releasing enterotoxins and cytotoxins that damage host cells and inducing inflammation – resulting in diarrhoea and other gastrointestinal symptoms.

EAEC is being increasingly recognised as an emerging enteric pathogen. In particular, EAEC is a common bacterial cause of paediatric diarrhoea, especially in developing countries. It has also been associated with traveller's diarrhoea and infections in HIV-infected individuals, as well as a cause of sporadic food-poisoning outbreaks in the developed world.^[1] Awareness of EAEC was increased by a serious outbreak in Germany during 2011, causing over 4000 cases and at least 50 fatalities. The pathogen responsible was found to be an EAEC O104:H4 strain which had acquired a Shiga toxin (usually associated with verotoxin-producing Escherichia coli).^[2]

Strains of EAEC are highly genetically heterogeneous, but some genes have been associated with virulence. A transcription factor named AggR, part of the AraC family of transcription activators, may regulate some of the virulence factors for EAEC. Several toxins have been linked to EAEC virulence, including ShET1 (Shigella enterotoxin 1), Pet (plasmid‐encoded toxin), and EAST-1. Other virulence factors include adhesins, with a family of bundle‐forming fimbriae termed aggregative adherence fimbria (AAF) found to be important in many EAEC strains.^[3]

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