Beta-Lactam Resistance

ESBL: Extended-Spectrum Beta-Lactamase

  • Organisms that have a beta-lactamase encoded on a plasmid, allowing for resistance to beta-lactam antibiotics, including extended-spectrum cephalosporins (such as 3rd generation cefotaxime, ceftriaxone, and ceftazidime), and aztreonam. Cefepime has suboptimal efficacy against these organisms
  • NOT resistant to carbapenems (so use these to treat if organism is identified to be ESBL-positive)
  • Organisms include:
    • E. coli
    • Pseudomonas aeruginosa
    • Klebsiella pneumoniae
    • Klebsiella oxytoca
    • Proteus mirabilis
    • Salmonella enterica
    • Neisseria gonorrhoeae
    • Haemophilus influenzae

AmpC-Inducible Beta-lactamase

  • Organisms that have an inducible beta-lactamase encoded in their chromosome, allowing for resistance to beta-lactam antibiotics, including extended-spectrum cephalosporins (such as 3rd generation cefotaxime, ceftriaxone, and ceftazidime), and aztreonam
  • NOT resistant to fourth-generation cephalosporins or carbapenems (so use these to treat)
  • Formerly: SPACE/SPICE used as a mnemonic to remember these organisms
    • Serratia
    • Pseudomonas aeruginosa
    • Acinetobacter
    • Indole-positive proteus (i.e. Proteus vulgaris)
    • Citrobacter
    • Enterobacter
    • Now also identified are Hafnia sp. and Providencia sp.

Carbapenemases

  • Several different organisms may potentially contain plasmids with carbapenemases, but the most notable is the KPC (Klebsiella pneumoniae carbapenemase) enzyme of the K. pneumoniae species.
  • Treatment is based off susceptibility testing

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