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Escherichia coli: a bacterium capable of both good and evil!

Posted By paula barbosa On In Scientific Blog | Comments Disabled

Introduction

Recent events at the start of summer 2025 remind us that the risk of food poisoning is very real and can have dramatic consequences. Following the discovery of contaminated pizzas a few years ago, a series of food poisoning incidents involving around 30 victims, a dozen hospitalisations and the death of a child were reported in France in the department of Aisne. The bacterium Escherichia coli was quickly identified as the culprit. A health alert and investigation traced the source of the contamination and a national health alert was issued. The source appears to be butchers who sold meat contaminated with the bacterium.

Figure 1: E. coli strain under electron microscopy

What is Escherichia coli (E. coli) ?

Figure 2 : A
16th-century Italian mummy from which fragments of E. coli DNA were extracted. Credit: Division of Paleopathology, University of
Pisa. (source: Science et Avenir)

A bit of history:

The genome of this bacterium has been reconstructed from fragments of a mummy dating back to the 16th century. However, there is little literature on any epidemics linked to this bacterium. This bacterium was isolated in 1885 by German paediatrician and bacteriologist Theodor Escherich (1857–1911), who was conducting research on the intestinal flora of newborns.

It is a commensal germ, meaning it lives in harmony with its host.

It is a Gram-negative bacterium found in the intestinal microbiota of warm-blooded animals and humans. There are several strains, most of which are fortunately harmless. They even have some particularly interesting properties, notably in relation to:

However, some bacteria, having acquired virulence factors, cause the release of toxins (Shiga toxins) that damage blood vessel cells in the intestines and kidneys. These are known as enterohaemorrhagic E. coli (EHEC).
Other strains have pathogenic properties (there are more than 100 listed):

What is less well known is that these bacteria are frequently handled and used in industry. They are used in particular in the production of biofuels and bioplastics, vaccines and therapeutic proteins (insulin, growth hormone), detergents, beer and food.

A brief focus on the use of this bacterium in genetic engineering: This bacterium has special qualities. It is easy to cultivate, its DNA can be easily manipulated, and many tools are available for mass production of foreign proteins.

How is it transmitted?

Contamination is mainly digestive, through the ingestion of contaminated food (undercooked meat, more rarely unwashed vegetables contaminated by livestock faeces, insufficiently purified water, etc.).
Human-to-human transmission often occurs within communities.

What are the symptoms?

Symptoms appear three to four days after infection and include diarrhoea, abdominal pain, vomiting and, in some cases, fever. The diarrhoea may be bloody, similar to haemorrhagic colitis. In the best case scenario, the prognosis is favourable and treatment is symptomatic. A severe form called haemolytic uraemic syndrome (HUS) can develop, which is precisely what happened in the Aisne department. In some cases, symptoms may appear up to 10 days after infection.

Qui est concerné ?

Everyone, but…
The most serious cases involve young children, people who are frail, the elderly… and people who are
susceptible to certain immune deficiencies.

How is the disease diagnosed?

Clinical examination and confirmation of dietary habits (raw meat, unwashed vegetables, etc.).
…), the appearance of identical cases in the immediate environment without these elements necessarily being present should raise suspicion of EHEC poisoning. The main additional test is laboratory analysis of stool samples to detect E. coli. As these are extremely numerous in the digestive tract, they must be differentiated in order to detect EHEC (those that carry the gene encoding Shiga toxin can be isolated, or Shiga toxin itself can be detected).

What is the recommended treatment?

Antibiotics are not routinely prescribed, as they are often contraindicated because destroying the bacteria can promote the release of the toxin1 [1]. Certain specific antibiotics may be administered depending on the severity of the symptoms.

Treatment is symptomatic for diarrhoea, promoting rehydration of patients (while avoiding anti-diarrhoea drugs in order to promote the elimination of the toxin through the stools). Disorders associated with HUS require more advanced resuscitation treatments (dialysis, transfusions, plasma
purification, etc.).

One treatment option involves the administration of synthetic antibodies.

Is there any prevention?

The main reservoir is the digestive tract of cattle2 [2]. It is difficult to eliminate the incidence of EHEC in livestock! If tests are carried out and come back positive, heat treatment or irradiation can be applied to the meat.

Prevention mainly involves strict food hygiene measures
For young children, the consumption of raw or undercooked meat and raw milk cheese is not recommended.
Antibiotics are not recommended for prophylaxis unless the immune system is compromised.

How common is the disease?

In France, there are approximately 150 to 200 serious cases per year. In the United States, 265,000 infections were reported in a single year caused3 [3] by Shiga toxin-producing E. coli, although not all of these cases were serious.
The World Health Organisation (WHO) estimates that, for 10% of patients, infection with Shiga toxin-producing E. coli can develop into HUS, with a mortality rate of 3 to 5%4 [4].

And what about the B in NRBC ?

Given the characteristics of this bacterium (easy production, easy genetic manipulation to produce toxins, etc.), could it be used as a biological weapon?
In theory, yes, but to turn it into a weapon requires a high level of genetic engineering expertise, there are risks for those handling it, and medical countermeasures exist. Furthermore, the health authorities have the means to detect it. This bacterium is therefore not currently considered a priority bioterrorism agent. However, this does not mean that it should not be monitored closely.

Focus on the classification of biological agents

For the record, pathogens are classified into categories

Escherichia coli is classified as category 2, but its highly pathogenic strains are classified as category6 [6].

Key points to remember


Short glossary of abbreviations:

Bibliography

  1. Oberc AM, Fiebig-Comyn AA, Tsai CN, Elhenawy W, Coombes BK. Antibiotics Potentiate
    Adherent-Invasive E. coli Infection and Expansion. Inflamm Bowel Dis. 2019 Mar
    14;25(4):711-721. doi: 10.1093/ibd/izy361. PMID: 30496418. ↩︎ [7]
  2. Kolenda R, Burdukiewicz M, Schierack P. A systematic review and meta-analysis of the
    epidemiology of pathogenic Escherichia coli of calves and the role of calves as reservoirs for human pathogenic E. coli. Front Cell Infect Microbiol. 2015 Mar 12;5:23. doi:
    10.3389/fcimb.2015.00023. PMID: 25815276; PMCID: PMC4357325. ↩︎ [8]
  3. https://my.clevelandclinic.org/health/diseases/16638-e-coli-infection ↩︎ [9]
  4. Par AFP le 31.03.2022 à 11h32 ↩︎ [10]
  5. https://www.inrs.fr/dms/inrs/CataloguePapier/DMT/TI-TO-30/to30.pdf ↩︎ [11]
  6. https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000044454319 ↩︎ [12]

Autor : Bruno Garrigue