Propionic acid and virulence of Crohn's-linked E. coli
What it found
In mice and lab tests, propionic acid made Crohn's-linked E. coli more virulent, more able to stick to gut cells and form biofilms, and better at surviving.
The same changes were seen in E. coli from Crohn's patients.
What they found
Animal and lab studies
More adhesion in mice
LF82 recovered from mice given propionic acid stuck to human gut cells 16 times better than the original strain. LF82 from mice given plain water showed no big change.
More biofilms in mice
LF82 from propionic acid-fed mice formed far more biofilm than the original strain. LF82 from control mice did not.
Lab-grown bacteria change
When LF82 was grown in lab medium with propionic acid as the only carbon source, it grew faster and stuck to gut cells 1.58 times better, invaded them 3.38 times better, and formed 1.34 times more biofilm.
Changes are reversible
Growing the propionic acid-exposed bacteria in rich medium without propionic acid for five cycles made them lose the extra virulence and return to levels similar to the original strain.
Survival in mice
In mice given propionic acid, the propionic acid-exposed LF82 persisted at more than 20 times higher levels in the ileum and more than 18 times higher in the colon compared with controls.
Human Crohn's isolates
E. coli isolates from children with Crohn's disease also became better at sticking to and invading gut cells after propionic acid exposure, and this change was reversible.
What the authors conclude
“Our data indicate that exposure to PA results in AIEC resistance and increased virulence in its presence.”
Also in their conclusions
- They say their data highlight the potential risks of widespread propionic acid use as an antimicrobial.
- They call for more work to determine the long-term effects of alternative antimicrobials in generating more resistant and more virulent bacteria capable of horizontal transmission.
- They advise that in addressing one resistance problem, we must be careful that another is not inadvertently created.
How it was done
Propionic acid is widely used in food and agriculture as an antimicrobial, and the authors wanted to see whether it could affect the virulence of Crohn's disease-associated adherent-invasive E. coli.
They gave mice drinking water with 20 mM propionic acid for 3 days before and during infection with the Crohn's-linked E. coli strain LF82, then checked the bacteria 21 days later. They also grew LF82 and E. coli isolates from Crohn's patients in lab medium with propionic acid as the only carbon source, and tested how well the bacteria stuck to and invaded human gut cells.
What it can’t tell you
- These are animal and lab studies. They cannot show what happens in people.
- The study used mice with propionic acid levels adjusted to mimic the human gut, so the results may not reflect real-life human exposure.
- The clinical E. coli isolates came from a small number of children with Crohn's disease, so the findings may not apply to all people.
Who paid
- Funding
- Funded by Wellcome Trust; Biotechnology and Biological Sciences Research Council (from the PubMed record).
- Conflicts
- Declaration of Interests R.H. has received conference travel expenses and consultancy fees from Nutricia-Danone and 4D Pharma. K.G. received research grants and speakers fees from Nestle Health Sciences, Nutricia-Danone, and Mylan.
- Authors work at
- University of Glasgow, UK; Heriot-Watt University, UK; Newcastle University, UK
The paper
- Title
- Propionic Acid Promotes the Virulent Phenotype of Crohn's Disease-Associated Adherent-Invasive Escherichia coli
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Ormsby MJ, Johnson SA, Carpena N, et al (2020). Propionic Acid Promotes the Virulent Phenotype of Crohn's Disease-Associated Adherent-Invasive Escherichia coli. Cell reports. doi:10.1016/j.celrep.2020.01.078Free full textPubMed 32075765DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error