Klebsiella pneumoniae

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Klebsiella pneumoniae

Structure and Physiology

Klebsiella pneumoniae is a Gram-negative, rod-shaped, facultative anaerobic bacterium. It is encapsulated and undergoes lactose fermentation for metabolic purposes when conditions allow. This nonmotile bacterium is found in humans within the normal flora of the mouth, skin, and intestines. It is a naturally occurring bacterium in the soil and some strains have the ability to fix nitrogen in anaerobic conditions.

Transmission and Disease

Klebsiella infections are most commonly seen in immunocompromised individuals but can elicit symptoms if aspirated into the lower respiratory tract. In the lungs, K.pneumoniae can cause inflammation and cell death through the process of necrosis that leads to hemorrhaging.


K. pneumoniae is relatively easy to disinfect and usually serves as a good representation of an antimicrobial agent’s efficacy against Gram-negative bacteria.


K. pneumoniae is present in mammals and ubiquitous in the ecological environment. The reason for its pathogenicity is largely due to the thick capsule layer that surrounds the bacterium.

  • Bialek-Davenet S, Lavigne JP, Guyot K, Mayer N, Tournebize R, Brisse S, Leflon-Guibout V, Nicolas-Chanoine MH. Differential contribution of AcrAB and OqxAB efflux pumps to multidrug resistance and virulence in Klebsiella pneumoniae. J Antimicrob Chemother. 04 Sep2014.