Enteroaggregative Escherichia coli: An Emerging Enteric Food Borne Pathogen

Abstract

Enteroaggregative Escherichia coli (EAEC) are quite heterogeneous category of an emerging enteric pathogen associated with cases of acute or persistent diarrhea worldwide in children and adults, and over the past decade has received increasing attention as a cause of watery diarrhea, which is often persistent. EAEC infection is an important cause of diarrhea in outbreak and non-outbreak settings in developing and developed countries. Recently, EAEC has been implicated in the development of irritable bowel syndrome, but this remains to be confirmed. EAEC is defined as a diarrheal pathogen based on its characteristic aggregative adherence (AA) to HEp-2 cells in culture and its biofilm formation on the intestinal mucosa with a "stacked-brick" adherence phenotype, which is related to the presence of a 60 MDa plasmid (pAA). At the molecular level, strains demonstrating the aggregative phenotype are quite heterogeneous; several virulence factors are detected by polymerase chain reaction; however, none exhibited 100% specificity. Although several studies have identified specific virulence factor(s) unique to EAEC, the mechanism by which EAEC exerts its pathogenesis is, thus, far unknown. The present review updates the current knowledge on the epidemiology, chronic complications, detection, virulence factors, and treatment of EAEC, an emerging enteric food borne pathogen.

Figure 1

Aggregative adherence pattern of EAEC. HEp-2 cells (10⁶) were grown to 50%–70% confluency as monolayers in a 6-well flat-bottom tissue culture plate. After overnight growth cells were washed and 2 mL of fresh DMEM media (pH 7.4) was added, and EAEC grown overnight at 37°C (215 rpm) was inoculated (25 μL) into the plate and incubated at 37°C overnight in 5% CO₂ atmosphere. Following incubation, the cells were washed, fixed, and stained with 2.5% Giemsa for 15 minutes. The adherence patterns were examined under 40-X magnification and photographed at 100-X magnification with digital camera in a light microscope. Data are a representative experiment from three independently performed experiments with similar results.