Researchers are seeing people in community health settings with extremely or unusually virulent strains of the bacteria Klebsiella pneumoniae. As a result, a National Institutes of Health research group is investigating how the immune system responds to the infection.
The scientists exposed the strains to human immune models in a test tube setting. They found some strains were more likely to survive in blood and serum than others. They also found that white blood cells were more apt to consume and destroy some strains more than others. The study was published in mBio.
Scientists have long known that K. pneumoniae is a source of infections. They knew it was most common in people already sick, those who were immunocompromised or those living in community settings such as long-term care facilities. Over the years, some strains have been more resistant to antibiotics, making it harder to treat them.
Some other strains of K. pneumoniae can cause severe infections in healthy people in community settings though they’re not multidrug-resistant; those are called hypervirulent K. pneumoniae, or hvKp. More recently, strains that have multidrug resistance and hypervirulence characteristics known as MDR hvKp, have been found in both settings.
In fact, classical K. pneumoniae (cKp) is the third most common pathogen found in hospital bloodstream infections.
Now, National Institute of Allergy and Infectious Diseases (NIAID) researchers are looking into whether the new strains can avoid human immune systems completely. They found the hvKp strains were more likely to survive in blood and serum than MDR hvKp strains. White blood cells devoured less than 5% of the hvKp strains, but more than 67% of the MDR hvKp strains (most of them were destroyed).
The potential severity of infection caused by MDR hvKp probably is in between the classical and hypervirulent forms, the researchers say. Classifying K. pneumoniae into cKp or hvKp should be reconsidered, they added.
The researchers say developing a vaccine to prevent and/or treat the infections is feasible.
“This important study is among the first to investigate interaction of these emergent Klebsiella pneumoniae strains with components of human host defense,” Hugh Auchincloss, MD, acting NIAID director said. “The work reflects the strength of NIAID’s Intramural Research Program. Having stable research teams with established collaborations allows investigators to draw on prior work and quickly inform peers about new, highly relevant public health topics.”
The researchers plan to look into what factors are involved in MDR hvKp’s susceptibility to the body’s immune system using mouse models.
