EFSA investigates EAEC as foodborne pathogen

By Joseph James Whitworth

- Last updated on GMT

EAEC health risks evaluated by EFSA panel

Related tags Foodborne outbreaks Escherichia coli

A panel of the European Food Safety Authority has identified surveillance and research needs for Enteroaggregative Escherichia coli (EAEC) as a foodborne pathogen.

EFSA asked the Panel on Biological Hazards (BIOHAZ) to deliver a Scientific Opinion​ on associated public health risks.

The panel said when investigating foodborne outbreaks, testing for EAEC should become routine in light of its apparent increasing involvement in mixed pathogen outbreaks.

It identified research needs such as development of PCR-based methods for detection and quantification of EAEC in food items and to better understand the routes by which humans are exposed to EAEC, methods for typing and comparative analysis of isolates collected from all potential reservoirs should be developed.

For surveillance needs, the panel suggested a survey of imported non-EU foods to quantify possible EAEC involvement.

It said evidence for animals and/or food being an important source is sparse and often based on identification of genes such as astA, which are not specific for EAEC, or in studies in parts of the world where pollution by human faecal waste is common.

BIOHAZ said sampling protocols for vegetables, herbs and fruits should be developed and applied.

What is known

Outbreaks associated with foods point to contamination by asymptomatic food handlers and poor sanitation.

The European Centre for Disease Prevention and Control (ECDC) data on cases of human disease and EFSA data on foodborne outbreaks were considered.

Gastroenteric E. coli strains are divided into six pathotypes based on pathogenicity profiles: EAEC, EPEC, STEC, EIEC (including Shigella spp.), ETEC and DAEC.

The panel said EAEC are characterised by ability to adhere to tissue culture cells in a distinct stacked-brick pattern mediated by aggregative adherence fimbriae (AAF), of which there are several known isoforms (I, II, III, IV and V). 

EAEC are a major cause of acute diarrhoeal illness in infants in many low-income countries and in travellers to and returning from such countries.

In higher-income countries it is increasingly involved in food-related incidents and outbreaks, and in non-gastroenteric infections such as urinary tract infections (UTIs).

EFSA databases were examined for foodborne outbreaks in 2007–2013 associated with STEC and other pathogenic E. coli.

Excluding waterborne outbreaks, 423 were reported in the six years, of which 97 were classified as outbreaks with strong evidence (2010–2013) or as verified outbreaks (2007–2009).

The causative agent was most commonly STEC O157, and occasionally Stx-producing EAEC O104:H4, STEC unspecified, Enterotoxigenic E. coli (ETEC) and Enteropathogenic E. coli (EPEC).

A variety of foods were reported to be the vehicle for pathogens in these outbreaks, including those of animal and non-animal origin.

Limited data

Information in relation to foodborne outbreaks related to EAEC is very limited, with the exception of reports relating to the 2011 EAEC O104:H4 outbreak, said the panel.

Specific data on EAEC are not collected so are not in the European Epidemiological Surveillance System (TESSy) database by the ECDC.

Methods to identify EAEC from diarrhoea include a PCR assay, clump formation test, glass slide adherence assay, and the HEp-2 cell adherence assay, there are no recommended definitive methods to identity it from food.

No country has an accredited method to detect EAEC in food/feed/animal samples, although in one country (which was not named) the National Reference Laboratory (NRL) foresees accreditation of the method of the EU Reference Laboratory (EURL) for E. coli including VTEC in 2016.

Whole genome sequencing (WGS) can provide data on the population structure of EAEC but has not been used routinely for identification from human infections or foods so further studies are needed to assess its potential.

Related topics Food Safety & Quality

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