Klebsiella

Article By:

Evans, Doyle J., Jr. Bacterial Enteropathogens Laboratory, Veterans Affairs Medical Center, Houston, Texas.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.365300

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• Klebsiella, published June 2014:Download PDF Get Adobe Acrobat Reader

A genus of Gram-negative, nonmotile, rod-shaped bacteria. Members of the genus Klebsiella (see illustration) are common bacterial organisms, but some have pathogenic significance. In general, Klebsiella bacteria ferment lactose, do not decarboxylate ornithine nor form hydrogen sulfide, and often produce large mucoid colonies and gas from glucose. Characteristic large mucoid colonies are the result of production of a large amount of capsular material. Some isolates, particularly those from urinary tract infections, produce a slow-acting urease enzyme. Species of Klebsiella are commonly found in soil and water, on plants, and in animals and humans. Harmless strains of Klebsiella are beneficial because they fix nitrogen in soil. Pathogenic species include K. pneumoniae, K. oxytoca, and K. granulomatis (formerly termed Calymmatobacterium granulomatis). In addition, there are three significant subspecies of K. pneumoniae—specifically, K. p. pneumoniae, K. p. ozaenae, and K. p. rhinoscleromatis. Klebsiella bacteria are Gram-negative-staining organisms, and species and strains can be differentiated by biochemical reactions. See also: Bacteria; Bacteriology; Medical bacteriology; Nitrogen fixation; Pathogen; Staining

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