Class C serine β-lactamase (AmpC) (AmpC)

Class C serine β-lactamases, commonly known as AmpC enzymes, are a critical class of bacterial enzymes that provide resistance to a wide array of β-lactam antibiotics, including penicillins, cephamycins, and most cephalosporins (Bush & Jacoby, 2010). These enzymes are typically found in Gram-negative bacteria such as Enterobacter, Citrobacter, and Pseudomonas aeruginosa, where they can be encoded on the chromosome or acquired via plasmids (Jacoby, 2009). Unlike Class A β-lactamases, AmpC enzymes are not effectively inhibited by traditional clinical inhibitors like clavulanic acid or sulbactam, posing a significant therapeutic challenge (Tamma et al., 2019). Their expression is often inducible, meaning exposure to certain antibiotics can trigger a massive increase in enzyme production, potentially leading to clinical failure even if the bacteria initially appeared susceptible (Meini et al., 2019). To address this, new therapeutic combinations involving diazabicyclooctane inhibitors, such as ceftazidime-avibactam, have been developed to neutralize the enzyme and restore antibiotic efficacy (Shirley, 2018). Understanding the prevalence and induction potential of AmpC is vital for effective antimicrobial stewardship and the management of multidrug-resistant infections.

Other names

AmpC β-lactamaseCephalosporinaseClass C beta-lactamaseSerine-type enterobacterial β-lactamaseGroup 1 β-lactamase

Inhibitors like avibactam and relebactam act by covalently binding to the active-site serine residue of the Class C β-lactamase, forming a stable enzyme-inhibitor complex that prevents the enzyme from degrading β-lactam antibiotics (Shirley, 2018; Tamma et al., 2019).