TABLE 1.

β-Lactamase classification schemesa

Ambler classBush-Jacoby-Medeiros classPreferred substratesInhibited by clavulanateRepresentative enzyme(s)
A (serine penicillinases)2aPenicillins+PC1 from S. aureus
2bPenicillins, narrow-spectrum cephalosporins+TEM-1, TEM-2, SHV-1
2bePenicillins, narrow-spectrum and extended- spectrum cephalosporins+SHV-2 to SHV-6, TEM-3 to TEM-26, CTX-Ms
2brPenicillinsTEM-30, SHV-72
2cPenicillins, carbenicillin+PSE-1
2eExtended-spectrum cephalosporins+FEC-1, CepA
2fPenicillins, cephalosporins, carbapenems±KPC-2, SME-1, NMC-A
B (metallo-β-lactamases)3Most β-lactams, including carbapenemsIMP-1, VIM-1, CcrA, and BcII (B1); CphA (B2); L1(B3)
C (cephalosporinases)1CephalosporinsAmpC, CMY-2, ACT-1
D (oxacillinases)2dPenicillins, cloxacillin±OXA-1, OXA-10
Not classified4
  • a Based on data from reference 57. An updated classification system by Bush and Jacoby is in press (56a) at the time of this writing.