Class C beta-lactamase (AmpC) (AmpC)

AmpC beta-lactamases are a class of enzymes (Ambler Class C) produced by various Gram-negative bacteria that confer resistance to a broad spectrum of beta-lactam antibiotics [1, 4]. These enzymes are serine-based hydrolases that specifically target and break down the beta-lactam ring of penicillins, most cephalosporins (including third-generation agents like ceftriaxone), and cephamycins such as cefoxitin [4, 7]. Unlike Class A beta-lactamases, AmpC enzymes are typically not inhibited by classical inhibitors like clavulanic acid or tazobactam, making them a significant clinical challenge [1, 9]. They are often encoded on the bacterial chromosome and can be induced to high levels of expression upon exposure to certain antibiotics, or they may become constitutively overexpressed through mutations in regulatory genes, a process known as derepression [1, 10]. Furthermore, the emergence of plasmid-mediated AmpC genes has allowed these resistance determinants to spread to species that do not naturally possess them, such as Klebsiella pneumoniae [4, 11]. In clinical practice, infections involving AmpC-producing organisms often require treatment with carbapenems or newer inhibitor combinations like ceftazidime-avibactam, which can effectively bypass or neutralize the enzyme's activity [1, 8].

Other names

Class C beta-lactamaseCephalosporinaseGroup 1 beta-lactamaseblaAmpCAmbler class C beta-lactamase

Beta-lactamase inhibitors bind to the active site serine of the AmpC enzyme, forming a stable covalent acyl-enzyme intermediate that prevents the hydrolysis of co-administered beta-lactam antibiotics.