Amino acid arginine restores last-resort antibiotic in mice
A Chinese study in mice found that pairing the antibiotic colistin with the amino acid L-arginine killed colistin-resistant E. coli; no human data yet.
Researchers at Sun Yat-sen University in China report that adding L-arginine, a common amino acid, to the antibiotic colistin killed E. coli bacteria that normally resist colistin. The work appears in Microbiology Spectrum and was reported by Phys.org on 29 October 2026, based on a release from the American Society for Microbiology. It is lab and animal research only, we found only this one report of the study, and we could not open the journal paper, so treat it as a single-source, preliminary result.
What the researchers did
The senior author is Guo-Bao Tian, a microbiologist at the university's Zhongshan School of Medicine. The team tested E. coli carrying a gene called mcr-1, which makes bacteria resistant to colistin. Colistin alone and L-arginine alone did little against these bacteria in the lab. Together they quickly killed them. Imaging with electron microscopes showed changes in the size and structure of the bacteria, including their membranes.
Why colistin matters
Colistin was approved in 1959. Phys.org says it was largely avoided for decades because of its toxicity and severe side effects, and came back into use as a last-resort drug for infections by gram-negative bacteria, a group that includes E. coli, once superbugs emerged in the 1990s. Resistance genes such as mcr-1 travel on plasmids, small rings of DNA that bacteria swap easily, which is how resistance spreads between strains. The wider problem is large: the World Health Organization says bacterial resistance was associated with more than 4.7 million deaths worldwide in 2021, and that too few new antibiotics are in development to replace failing ones.
What happened in mice
In mice with an abdominal infection from a colistin-resistant E. coli strain, 80% survived to 72 hours with colistin plus arginine. Survival was 40% with colistin alone and 0% with arginine alone. The combination also cleared more bacteria from major organs. The researchers propose a mechanism: the pair alters the bacterial membrane so colistin can enter the cell, and once inside it triggers reactive oxygen species, chemicals that damage and kill the cell. Think of arginine as propping open a locked door so the antibiotic can get in. Tian called it "a rational strategy to overcome colistin resistance."
What is confirmed and what is not
Confirmed by the report: the lab killing effect, the mouse survival figures and the proposed mechanism, all from the researchers' own work. Not reported: the number of mice per group, the doses used, and which genes were identified, so we cannot judge how strong the survival gap is. A difference of 80% against 40% could come from only a handful of animals. Unknown: whether the effect holds in other resistant strains, other infection sites, or people. The researchers themselves say safety and effectiveness need more testing before human use, and that the strains tested may not represent all resistant bacteria. Mouse results often do not carry over to patients.
What it means for readers
In India, resistant infections are a concern for hospitals and families alike. WHO says resistance is highest in the South-East Asia and Eastern Mediterranean regions, where about one in three reported infections were resistant. That is why low-cost add-ons that could revive older drugs get attention. This finding is an early lead, not a treatment. Nobody should take arginine or any supplement to treat an infection, and antibiotics should be used only as prescribed.
What to watch next
Watch for the full paper's methods, with group sizes and doses, and for independent labs repeating the result in other resistant strains. A first safety study in animals, and any plan for human trials, would be the next real tests. No dates have been announced.
Key takeaways
- A Chinese team reports that L-arginine makes colistin kill colistin-resistant E. coli in the lab and in mice.
- In infected mice, 80% survived to 72 hours with the combination, against 40% on colistin alone.
- The report gives no group sizes or doses, and there are no human data.
- This is a single-source, preliminary finding and is not a treatment or medical advice.
Sources
- [Phys.org: Amino acid boosts last-resort antibiotic's effectiveness](https://phys.org/news/2026-10-amino-acid-boosts-resort-antibiotic.html)
- [WHO: Antimicrobial resistance fact sheet](https://www.who.int/news-room/fact-sheets/detail/antimicrobial-resistance)
Tags: Antibiotic resistance Colistin Amino acids E. coli Preclinical research