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Scientific classification
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Enterobacteriales
Family: Enterobacteriaceae
Genus: Klebsiella
Trevisan 1885

K. granulomatis
K. oxytoca
K. pneumoniae
K. terrigena
K. planticola (until 2001)

Klebsiella is a genus of nonmotile, Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule.[1] It is named after the German microbiologist Edwin Klebs (1834–1913).

Klebsiella species are found everywhere in nature. This is thought to be due to distinct sublineages developing specific niche adaptations, with associated biochemical adaptations which make them better suited to a particular environment. They can be found in water, soil, plants, insects, animals, and humans.[2][3]

List of species of the genus Klebsiella[edit]

  • K. granulomatis
  • K. oxytoca
  • K. michiganensis
  • K. pneumoniae (type-species)
    • K. p. subsp. ozaenae
    • K. p. subsp. pneumoniae
    • K. p. subsp. rhinoscleromatis
  • K. quasipneumoniae
    • K. q. subsp. quasipneumoniae
    • K. q. subsp. similipneumoniae
  • K. variicola


Klebsiella bacteria tend to be rounder and thicker than other members of the Enterobacteriaceae family. They typically occur as straight rods with rounded or slightly pointed ends. They can be found singly, in pairs, or in short chains. Diplobacillary forms are commonly found in vivo.[4]

They have no specific growth requirements and grow well on standard laboratory media, but grow best between 35 and 37 °C and at pH 7.2. The species are facultative anaerobes, and most strains can survive with citrate and glucose as their sole carbon sources and ammonia as their sole nitrogen source.[4]

Members of the genus produce a prominent capsule, or slime layer, which can be used for serologic identification, but molecular serotyping may replace this method.[5]

Klebsiella in humans[edit]

Klebsiella species are routinely found in the human nose, mouth, and gastrointestinal tract as normal flora; however, they can also behave as opportunistic human pathogens.[4] Klebsiella species are known to also infect a variety of other animals, both as normal flora and opportunistic pathogens.[2]

Klebsiella organisms can lead to a wide range of disease states, notably pneumonia, urinary tract infections, septicemia, meningitis, diarrhea, and soft tissue infections.[4][6] Klebsiella species have also been implicated in the pathogenesis of ankylosing spondylitis and other spondyloarthropathies.[7] The majority of human Klebsiella infections are caused by K. pneumoniae, followed by K. oxytoca. Infections are more common in the very young, very old, and those with other underlying diseases, such as cancer,[2] and most infections involve contamination of an invasive medical device.[4]

During the last 40 years, many trials for constructing effective K. pneumoniae vaccines have been tried. Currently, no Klebsiella vaccine has been licensed for use in the US. K. pneumoniae is the most common cause of nosocomial respiratory tract and premature intensive care infections, and the second-most frequent cause of Gram-negative bacteraemia and urinary tract infections. Drug-resistant isolates remain an important hospital-acquired bacterial pathogen, add significantly to hospital stays, and are especially problematic in high-impact medical areas such as intensive care units. This antimicrobial resistance is thought to be attributable mainly to multidrug efflux pumps.[8] The ability of K. pneumoniae to colonize the hospital environment, including carpeting, sinks, flowers, and various surfaces, as well as the skin of patients and hospital staff, has been identified as a major factor in the spread of hospital-acquired infections.[2][9]

Klebsiella in plants[edit]

In plant systems, Klebsiella can be found in a variety of plant hosts. K. pneumoniae and K. oxytoca are able to fix atmospheric nitrogen into a form that can be used by plants, thus are called associative nitrogen fixers or diazotrophs.[3][10] The bacteria attach strongly to root hairs and less strongly to the surface of the zone of elongation and the root cap mucilage.[11] They are bacteria of interest in an agricultural context, due to their ability to increase crop yields under agricultural conditions.[12] Their high numbers in plants are thought to be at least partly attributable to their lack of a flagellum, as flagella are known to induce plant defenses.[13]

See also[edit]



  1. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. p. 370. ISBN 0-8385-8529-9. 
  2. ^ a b c d Bagley S (1985). "Habitat association of Klebsiella species". Infect Control 6 (2): 52–8. PMID 3882590. 
  3. ^ a b Brisse S, Grimont F & Grimont P AD (2006). Prokaryotes. New York, NY: Springer New York. pp. 159–196. 
  4. ^ a b c d e Ristuccia, Patricia A; Cunha Burke A (1984). "Klebsiella". Topics in Clinical Microbiology 5 (7): 343–348. JSTOR 30144997. 
  5. ^ Brisse, Sylvain; S Issenhuth-Jeanjean; P AD Grimont (2004). "Molecular Serotyping of Klebsiella Species Isolates by Restriction of the Amplified Capsular Antigen Gene Cluster". Journal of clinical Microbiology 42 (8): 3388–3398. doi:10.1128/jcm.42.8.3388-3398.2004. 
  6. ^ Podschun R, Ullmann U (1998). "Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors". Clin Microbiol Rev 11 (4): 589–603. PMC 88898. PMID 9767057. 
  7. ^ Sieper, Joachim; Braun, Jürgen (2011). Ankylosing Spondylitis in Clinical Practice. London: Springer-Verlag. p. 9. ISBN 978-0-85729-179-0. Retrieved October 10, 2012. 
  8. ^ Ogawa, Wakano; Li, Dai-Wei Yu, Ping Begum, Anowara Mizushima, Tohru Kuroda, Teruo Tsuchiya, Tomofusa (2005). "Multidrug resistance in Klebsiella pneumoniae MGH78578 and cloning of genes responsible for the resistance". Biological & Pharmaceutical Bulletin 28 (8): 1505–1508. doi:10.1248/bpb.28.1505.  Cite uses deprecated parameter |coauthors= (help)
  9. ^ Jadhav, Savita; Rabindranath Misra; Nageshawari Gandham; Mahadev Ujagare; Purbasha Ghosh; Kalpana Angadi; Chanda Vyawahare (2012). "INCREASING INCIDENCE OF MULTIDRUG RESISTANCE klebsiella pneumoniae INFECTIONS IN HOSPITAL AND COMMUNITY SETTINGS". International Journal of Microbiology Research 4 (6): 253–257. doi:10.9735/0975-5276.4.6.253-257. 
  10. ^ Cakmaki ML, Evans HJ, Seidler RJ (1981). "Characteristics of a nitrogen-fixing Klebsiella oxytoca isolated from wheat roots". Plant and Soil 61: 53–64. doi:10.1007/BF02277362. 
  11. ^ Haahtela, K; Laakso T; Korhonen TK (1986). "Associative nitrogen fixation by Klebsiella spp.: Adhesion sites and innoculation effects on grass roots". Applied Environmental Microbiology 52: 1074–1079. 
  12. ^ Riggs, PJ; Chelius MK; Iniguez AL; Kaeppler SM; Triplett EW (2001). "Enhanced maize productivity by inoculation with diazotrophic bacteria". Australian Journal of Plant Physiology 28 (9): 829–836. doi:10.1071/PP01045. 
  13. ^ Fouts, Derrick E.; Tyler, Heather L.; Deboy, Robert T.; Daugherty, Sean; Ren, Qinghu; Badger, Jonathan H.; Durkin, Anthony S.; Huot, Heather; Shrivastava, Susmita; Kothari, Sagar; Dodson, Robert J.; Mohamoud, Yasmin; Khouri, Hoda; Roesch, Luiz F. W.; Krogfelt, Karen A.; Struve, Carsten; Triplett, Eric W.; Methé, Barbara A. (2008). "Complete Genome Sequence of the N2-Fixing Broad Host Range Endophyte Klebsiella pneumoniae 342 and Virulence Predictions Verified in Mice". PLoS Genetics 4 (7): e1000141. doi:10.1371/journal.pgen.1000141. PMC 2453333. PMID 18654632.  open access publication - free to read

External links[edit]