Klebsiella pneumoniae
Gut bacterium behind hospital pneumonia and bloodstream infections; a leading drug-resistant pathogen.
Klebsiella pneumoniae causes hospital pneumonia and bloodstream infections, and its carbapenem-resistant form topped WHO's 2024 Bacterial Priority Pathogens List, ahead of 23 other pathogens.
Last refreshed: 4 October 2026
Background
Klebsiella pneumoniae now leads the spread of drug-resistant gut bacteria in Europe. In its threats report for 26 September to 2 October 2026, ECDC described a "substantially worsening" situation for carbapenem-resistant Enterobacterales across the EU/EEA, driven by this species. A European genomic survey and network investigations found a rising share and wider spread of K. pneumoniae carrying NDM carbapenemases, enzymes that defeat last-resort antibiotics, and of strains also carrying genes for higher virulence.
The resistance now reaches the newest drugs. ECDC says NDM enzymes confer resistance to ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam, antibiotics introduced in the EU/EEA within the last ten years to treat these infections. It traced cross-border spread of plasmids carrying both resistance and virulence genes, and of new strains such as ST6668, through patient transfers and hospital referral networks. ECDC plans to update its rapid risk assessment, last issued on 3 February 2025.
Its threat rests on the hospital infections it causes. WHO's 2024 Bacterial Priority Pathogens List ranked carbapenem-resistant K. pneumoniae first of 24 pathogens, in the critical tier.