Klebsiella pneumoniae is a gram-negative, lactose-fermenting, non-motile, aerobic rod-shaped bacterium. It has been a known human pathogen since it was first isolated in the late nineteenth century by Edwin Klebs.
The microbiology, pathogenesis, and epidemiology of infections due to K. pneumoniae will be reviewed here. The epidemiology, clinical manifestations, diagnosis, and treatment of infections due to this organism are discussed separately. (See "Clinical features, diagnosis, and treatment of Klebsiella pneumoniae infection".)
K. pneumoniae has three subspecies with homologous DNAs but different biochemical reactions: K. pneumoniae subsp pneumoniae, K. pneumoniae subsp ozaenae, and K. pneumoniae subsp rhinoscleromatis. For the remainder of this topic review, K. pneumoniae will specifically refer to K. pneumoniae subsp pneumoniae.
The following are the characteristic biochemical reactions of the different organisms:
●K. pneumoniae is lactose fermenting, H2S- and indole-negative, has a positive Voges-Proskauer (VP) reaction, is capable of growth in KCN and using citrate as a sole carbon source, and is incapable of growth at 10ºC.