Klebsiella species is a topic covered in the Johns Hopkins ABX Guide.

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MICROBIOLOGY

  • Gram-negative, lactose fermenting aerobic bacilli of Enterobacteriaceae family.
    • K. pneumoniae, K. oxytoca and K. granulomatis.
      • K. ozaenae and K. rhinoscleromatis are non-fermenting subspecies.
    • Forms highly mucoid colonies w/polysaccharide capsule, a virulence factor that inhibits phagocytosis. Easily cultured on non-selective media for sterile specimens or MacConkey agar for contaminated specimens.
    • Known to contaminate drains[14] and serve as point source for nosocomial outbreaks, esp. K. pneumoniae, K. oxytoca (as well as E. coli., Pseudomonas and Acinetobacter species).[7]
  • Resistance issues:
    • Beta-lactamases are constitutive, usually produced at low levels, and provide resistance against ampicillin, amoxicillin and ticarcillin.
      • Few klebsiellae lack these beta-lactamases.
    • Extended-spectrum beta-lactamases (ESBLs): may be plasmid-mediated or chromosomal, confer multidrug resistance (TEM or SHV types), and are detected by in vitro resistance to ceftazidime and aztreonam.
      • CTX-M type ESBLs are the most prevalent ESBL types worldwide and are commonly associated with ST131 E. coli.[19]
    • Carbapenemases:
      • Klebsiella pneumoniae carbapenemase, KPC (Ambler Class A): confers broad resistance and is associated with mortality rate >50%.[12]
        • Many isolates in US are sequence type, ST258.
        • Susceptibility limited to gentamicin, tigecycline and colistin.
        • Inhibited by clavulanic acid and tazobactam.
      • Metallo-beta-lactamases (Ambler Class B): types include IMP (imipenemase), VIM (Verona integron-encoded MBL), and NDM-1 (New Delhi MBL).
        • Require zinc ions in the active site for activity.
        • IMP and VIM are not resistant to aztreonam.
        • NDM-1 generally resistant to all antibiotics (including aztreonam and aminoglycosides) except tigecycline and colistin.
      • OXA-type carbapenemases (Ambler Class D): include OXA-48, weakly hydrolyze carbapenems, broad-spectrum cephalosporins, and aztreonam; express resistance or decreased susceptibility to carbapenems.
        • Often associated with Acinetobacter baumannii.

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Last updated: October 13, 2016