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Table 2 Major groups of β-lactamases in Gram-negative bacteria that threaten the role of β-lactam antibiotics

From: Bench-to-bedside review: The role of β-lactamases in antibiotic-resistant Gram-negative infections

    β-Lactams to which resistance is conferred
Functional groupa Molecular classb Common name Primaryc Secondaryd
1 C Cephalosporinase Penicillins, cephalosporins Carbapenems, monobactams
2b A Penicillinase Penicillins, early cephalosporins β-lactamase inhibitor combinations
2be A Extended-spectrum
Penicillins, cephalosporins, monobactams, β-lactamase inhibitor combinations None
2d D Cloxacillinase Penicillins, including oxacillin and cloxacillin None
2df D Carbapenemase Carbapenems and other β-lactams None
2f A Carbapenemase All current β-lactams None
3 B Metallo-β-lactamase All β-lactams except monobactams None
  1. aClassification based on Bush, Jacoby, and Medeiros [11] and Bush and Jacoby [7]. bClassified according to primary amino acid sequence [810]. cβ-lactams that are resistant solely as a function of β-lactamase production. dβ-lactams that are resistant as a function of β-lactamase production, usually at high levels, in combination with efflux or porin modifications.