# A woman got a UTI. Two years later, the bacteria had evolved, invaded her brain.

- URL: https://talkfuse.com/story/a-woman-got-a-uti-two-years-later-the-bacteria-had-evolved-invaded-her-brain/
- Published: 2026-07-23T16:58:26+00:00
- Updated: 2026-07-23T22:46:25+00:00
- Original publisher: Ars Technica
- Original article: https://arstechnica.com/health/2026/07/woman-loses-vision-in-one-eye-after-uti-bacteria-evolves-to-invade-her-brain/
- Topics: Software

## Key points

- UTI bacteria evolved into a brain-invading, hypervirulent form.
- The infection caused vision loss and a brain abscess.
- Mutations produced a protective sticky bacterial capsule.

## Summary

A 63-year-old woman suddenly lost sight in her right eye and was found to have inflammation there alongside brain lesions caused by a bacterial abscess. Tests linked the infection to Klebsiella pneumoniae first detected in her urine, illustrating how bacteria can evolve within a patient into forms capable of spreading through the bloodstream and damaging distant organs.

Doctors found that later urine and brain samples contained a sticky, capsule-rich, hypervirulent form of the bacterium, unlike an earlier ordinary-looking urine sample. Genome sequencing showed the samples were closely related but had acquired mutations affecting capsule production; the altered bacteria resisted immune cells and proved lethal in mice, although they grew more slowly and infected bladder cells less effectively.

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