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

A 63-year-old woman presented with vision loss and brain lesions, revealing a Klebsiella pneumoniae infection that had spread from her urinary tract. Medical investigation discovered distinct bacterial strains: one normal, and two hypervirulent strains with thick capsules that made them more dangerous and resistant to immune cells. This case demonstrates ‘heterovirulence,’ where different bacterial populations with varying fitness advantages can coexist and evolve within a single patient.

• A woman experienced vision loss and brain inflammation due to Klebsiella pneumoniae infection.
• Initial samples showed normal bacteria, but subsequent samples from urine and brain revealed hypervirulent strains with thick capsules.
• These hypervirulent bacteria were more resistant to immune cells but grew slower and were less effective at infecting the bladder.
• Genome sequencing indicated the hypervirulent strains evolved from a common ancestor within one to two years prior to the woman’s severe symptoms.
• The woman had a urinary tract infection hospitalization two years before her brain abscess, suggesting the origin of the infection.
• This phenomenon, termed ‘heterovirulence,’ shows bacterial evolution and adaptation within a single patient.
• The patient was successfully treated with antibiotics, and all bacterial isolates were susceptible to treatment.
  Continue reading https://arstechnica.com/health/2026/07/woman-loses-vision-in-one-eye-after-uti-bacteria-evolves-to-invade-her-brain/