Klebsiella spp.

  • Douglas I. Johnson


  • Genomics:
    • Klebsiella pneumoniae strain MGH78578 chromosome: 5,315,120 bp; 4776 predicted ORFs (Lery et al. 2014)

  • Cell morphology:
    • Rod-shaped cells (Fig. 18.1)

    • Nonmotile

    • Capsule: major virulence factor (Fig. 18.1; see below)

    • Lipopolysaccharide (LPS): immunostimulatory; associated with inflammation and endotoxic shock; also functions in immune evasion (see below)

  • Gram stain:
    • Gram negative

  • Growth:
    • Facultative anaerobes; oxidase negative.

    • Urease positive; used to obtain nitrogen from host urea.

    • Reservoirs: contaminated soil and surface water; human hosts (primary).

    • Can colonize human mucosal layers, including the gastrointestinal tract and the nasopharynx.

    • Excellent biofilm formers (see below).

    • Six species and several subspecies: K. pneumoniae is the primary human pathogen; K. oxytoca is next most prevalent:
      • K. pneumoniae strains can be classified as either classical or hypervirulent (HV).

      • K. pneumoniae strains are serotyped by LPS (O) antigens and capsular (K) antigens:
        • 9 O antigen serotypes: O1 (most common)

        • 78 K antigen serotypes: K1–K78

      • Member of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) family of antibiotic-resistant nosocomial pathogens.

      • Significant increases worldwide in antibiotic-resistant strains and HV strains:
        • Antibiotic resistance – two major mechanisms:
          • Expression of carbapenemases; display resistance to all β-lactam antibiotics.

          • Isolates can be found worldwide.

          • Antibiotic resistance does not increase the virulence of these strains.

        • HV strains (Paczosa and Mecsas 2016; Patel et al. 2014; Shon et al. 2013):
          • Predominantly O1:K1 (93%) and O1:K2 strains.

          • Exhibit a hypermucoviscous phenotype on agar plates; due to the presence of a hypercapsule with increased production of capsule polysaccharide (CPS).

          • Also increased production and utilization of iron siderophores enterobactin, yersiniabactin, salmochelin, aerobactin.

          • Isolates are found predominantly in Southeast Asia and Taiwan, although incidents are spreading worldwide.


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Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  • Douglas I. Johnson
    • 1
  1. 1.Department of Microbiology & Molecular GeneticsUniversity of VermontBurlingtonUSA

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