Skip to main content
. 2024 Jul 13;13(7):648. doi: 10.3390/antibiotics13070648

Table 2.

Ambler Classification System.

Class Catalytic Center Examples
(Enzymes)		 Substrate
(Target)		 Inhibited by
(Treatment)
A Serine TEM-1, SHV-1
(penicillinases)		 Penicillins

  • Amoxicillin-clavulanic acid

  • Ampicillin-sulbactam

  • Most cephalosporins
CTX-M
(ESBL)		 Cephalosporins

  • Piperacillin-tazobactam (cystitis)

  • Cefepime (cystitis)

  • Carbapenems

  • Fluroquinolones
KPC
(Carbapenemases)		 Carbapenems

  • Ceftazidime-avibactam

  • Meropenem-vaborbactam

  • Imipenem-cilastatin-relebactam

  • Cefiderocol

  • Fluoroquinolones
B Zinc IMP, VIM, NDM All beta-lactam antibiotics (not aztreonam)

  • Aztreonam + avibactam

  • Cefiderocol

  • Cefepime-taniborbactam (not FDA approved)

  • Xeruborbactam (not FDA approved)
C Serine AmpC Penicillins and most
cephalosporins

  • Cefepime

  • Carbapenems

  • Fluroquinolones
D Serine OXA Penicillins, cephalosporins, and carbapenems
(depends on OXA subtype)

  • Amoxicillin-clavulanic acid

  • Ampicillin-sulbactam

  • Piperacillin-tazobactam

  • Ceftazidime-avibactam (OXA-48)

  • Cefiderocol (OXA-48)

  • Fluoroquinolones

Abbreviations: CTX-M (cefotaxime-hydrolyzing beta-lactamase isolated in Munich), IMP (active on imipenem) (imipenem-hydrolyzing beta-lactamase); KPC (Klebsiella pneumoniae carbapenemase); NDM (New Delhi metallo-beta-lactamase); OXA (oxacillinase), SHV (Sulfhydryl reagent variable); TEM (Temoneira); VIM (Verona integron-encoded metal-beta-lactamase).