NIH Researchers Investigate Hypervirulent Klebsiella pneumoniae Strain

Yesterday, the National Institutes of Health (NIH) announced an investigation into Klebsiella pneumoniae, a bacterium that has managed to infect multiple healthy people in community settings. The insights into this microbe were led by researchers at the National Institute of Allergy and Infectious Disease (NIAID), a subset of the NIH.

Laboratory-based studies revealed that certain strains of K. pneumoniae can survive in blood and serum, while neutrophils ingest and kill other strains.

“This important study is among the first to investigate the interaction of these emergent Klebsiella pneumoniae strains with components of human host defense,” acting NIAID Director Hugh Auchincloss, MD, said in the NIH press release. “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.”

Historically, K. pneumoniae has caused severe and fatal infections in hospital settings. The bacteria were more likely to impact those with a compromised immune system. However, researchers note that the development of multiple antibiotics and subsequent antibiotic resistance have caused the emergence of more strains that are difficult to treat.

The most common strain in hospital settings is classical K. pneumoniae (cKp), one of the most common hospital bloodstream infections. Beyond cKp, two strains commonly cause infections in community settings: hypervirulent K. pneumoniae (hvKp) and strains with multidrug-resistant and hypervirulent properties (MDR hvKp).

The researchers examining these strains were from Rocky Mountain Laboratories in Hamilton, Montana. Evaluating the interactions between the strains and neutrophils, the researchers discovered that hvKp is more likely to survive in the bloodstream. Neutrophils could ingest and kill 67% of MDR hvKp strains; however, they only attacked 5% of hvKp strains.

“Based on the findings, the researchers suggest that the potential severity of infection caused by MDR hvKp likely falls in between the classical and hypervirulent forms. The work also suggests that the widely used classification of K. pneumoniae into cKp or hvKp should be reconsidered,” explained the NIH release.

Future studies will explore why MDR hvKp is more easily attacked by the human immune system using mouse infection models.