Researchers rush to study if caffeine boosts E. coli antibiotic resistance

Caffeine might help certain bacteria fend off antibiotics by altering how drugs enter their cells, according to a new lab-based study — but experts emphasise that there’s no immediate cause for concern among coffee lovers.

The research suggests that caffeine could influence bacterial resistance by interfering with the production of transport proteins that typically allow antibiotics to enter bacterial cells. The LiveScience publication reported on this finding but underscores that it remains unknown how this might impact real-world treatment in humans.

Bacteria have long been known to defend themselves using specialised proteins embedded in their outer membranes. These transport proteins can expel harmful chemicals, including antibiotics, before the drugs can do damage. What’s less understood is how the genes behind these proteins get switched on or off depending on what the bacteria encounter in their environment.

To investigate this, scientists based at the University of Tübingen in Germany tested the common gut bacterium Escherichia coli — or E. coli — against a wide range of 94 chemical substances. These included well-known drugs like antibiotics and aspirin, naturally occurring gut compounds such as bile acids, and small molecules found in everyday foods — among them, caffeine and vanillin, the flavouring in vanilla.

The findings, published July 22 in the journal PLOS Biology, showed that many of these chemicals triggered changes in the expression of genes tied to transport proteins, potentially altering how susceptible bacteria are to antibiotics.

In the case of caffeine, researchers observed that it appeared to reduce the production of a specific transport protein called OmpF. This protein plays a role in helping antibiotics — such as ciprofloxacin and amoxicillin — enter bacterial cells. With less OmpF available, it’s harder for these drugs to penetrate the cell membrane, which could theoretically reduce their effectiveness.

The researchers focused on seven transport-related genes in E. coli. Of the 94 compounds tested, 28 were found to influence the expression of at least one of these genes. Some of the substances that had an impact included caffeine, the herbicide paraquat, certain antibiotic classes like tetracyclines and macrolides, folic acid blockers (used in cancer and autoimmune treatments), and salicylates, a group of compounds that includes aspirin.

"This study adds to a growing appreciation that bacteria can sense and respond to numerous different stimuli … all of which can affect the susceptibility of the microbe to antibiotics," said Andrew Edwards, a professor of molecular microbiology at Imperial College London.

Still, experts are urging caution in interpreting the results. April Hayes, a postdoctoral researcher at the University of Exeter who was not involved in the research, said more work is needed to assess how these lab findings might translate into real-life outcomes. “This would include whether the effect of caffeine would reduce the body's ability to clear infections,” Hayes told Live Science.

Edwards echoed that view, stressing that the new findings don't mean caffeine has a measurable impact on how antibiotics work in the human body. “There’s no evidence from this study that drinking coffee will affect a person's response to antibiotics, and nobody should change their routine,” he said.

He added that people prescribed antibiotics should continue following their doctor’s instructions and read all accompanying guidance that comes with their medications. Until more studies are done — particularly those that explore how caffeine interacts with antibiotics in the human body — there’s no reason to believe that a morning cup of coffee poses any risk to treatment outcomes.

By Nazrin Sadigova