Definitions:

• Beta lactamase: Hydrolytic enzyme that acts on a beta lactam to cleave the beta-lactam ring
• ESBL Extended spectrum beta lactamase
• CRO - carbapenem resistant organism (any bug, any mechanism)
• CPO - carbapenemase producing organism (any bug, carbapenemase)
• CRE – carbapenem resistant enterobacterales (Enterobacterales, any mechanism)
• CPE - carbapenemase producing enterobacterales (Enterobacterales, carbapenemase)

This elegantly drawn diagram explains the differences:

Look, don’t judge me, I’m a podcaster not an artist.

History of resistance

How Resistance mechanisms spread in the population:

Ambler Classification (including carbapenemases)

• A: active site serine B-lactamase
  • ESBL
    • TEM
    • SHV-1
    • CTX-M
  • KPC carbapenemase
• B: Metallobetalactamases
  • Require bivalent metal ion, usually zinc
  • NDM, VIM, IMP
• C: serine betalactmases
  • AmpC