AmpCproducing

AmpCproducing refers to bacteria that produce AmpC beta-lactamase, an enzyme that can hydrolyze many beta-lactam antibiotics and thereby confer resistance. AmpC enzymes are class C beta-lactamases and are not reliably inhibited by clavulanic acid, making AmpC-mediated resistance harder to counter than many other beta-lactamases.

AmpC beta-lactamases can be encoded on the chromosome or on plasmids. Chromosomal AmpC is common in several Enterobacterales species (for example Enterobacter, Citrobacter, Serratia, Hafnia), where expression can be inducible or derepressed, leading to variable resistance during therapy. Plasmid-mediated AmpC genes (pAmpC), including families such as CMY, DHA, FOX, ACC, MOX, and others, can spread between species and contribute to broader resistance. Plasmid-associated AmpC enzymes often confer high-level resistance and may accompany other resistance determinants, such as ESBLs or carbapenemases.

Clinically, AmpC producers pose therapeutic challenges, particularly in hospital settings where resistant infections are more common. They can reduce susceptibility to many cephalosporins and cephamycins, and treatment choices depend on susceptibility testing. Carbapenems are commonly effective, especially for serious infections. Some non-carbapenem options may be viable if the isolate remains susceptible, and beta-lactamase inhibitors with activity against AmpC (for example, avibactam-containing combinations) can restore activity against certain AmpC producers. Temocillin may retain activity in some settings. Detection in the laboratory relies on phenotypic screens (such as cefoxitin resistance) and confirmatory tests for AmpC, or molecular methods to identify specific ampC genes.

Infection control and antibiotic stewardship are important to limit spread and preserve future treatment options for AmpC-producing organisms.