Using advanced genome sequencing techniques, researchers have determined that the bacterial strains in two urine samples diverged from a common ancestor just one to two years prior to the woman’s current medical condition. Recently, a highly virulent strain of urinary bacteria has been found spreading to women’s brains.
The patient’s medical history reveals that two years before developing a brain abscess, she experienced a hospitalization for a urinary tract infection (UTI).
Understanding Heterovirulence
Bacterial evolution within a single patient is a well-documented phenomenon. Pathogenic bacteria often adapt to enhance their fitness for survival. Usually, the variant with the greatest advantage will dominate the population. However, sometimes bacteria can split into different groups, particularly when facing antibiotic treatments. In these instances, some mutant strains develop increased resistance but may also incur disadvantages such as slower growth rates and reduced virulence, which can complicate treatment efforts. This situation is termed “heterotolerance” and is closely linked to treatment failures.
Fortunately, in this particular case, all three bacterial isolates from the patient were found to be antibiotic-susceptible, allowing for effective infection resolution through antibiotic therapy. Most patients infected with Klebsiella pneumoniae typically encounter similar outcomes. While the brain abscess ultimately resolved, there was no subsequent follow-up regarding the patient’s neurological or visual recovery.
Interestingly, her infection was not characterized by heteroresistance, but rather by a phenomenon known as heterovirulence. The highly virulent subpopulation exhibited a physical disadvantage in the urinary tract, which is where the infection originated. Nevertheless, it retained a significant advantage in terms of transmission and toxicity, as evidenced by its spread to the brain and eyes.
In summary, researchers and healthcare professionals emphasize that “this case highlights the remarkable ability of Klebsiella pneumoniae to transmit and evolve within the patient’s body, affecting distant sites from the original clinical reservoir in the urinary tract.”
Source: arstechnica.com