On Sept. 6, 2023, the National Institutes of Health (NIH) announced it was investgating ‘hypervirulent’ strains of the bacterium Klebsiella pneumoniae that have emerged in healthy people in community settings.

After exposing the strains to components of the human immune system in a laboratory “test tube’ setting, scientists found that some strains were more likely to survive in blood and serum than others, and that neutrophils (white blood cells) are more likely to ingest and kill some strains than others. The study, published in mBio, was led by researchers at NIH’s National Institute of Allergy and Infectious Diseases (NIAID).