AmpC β-Lactamase-Producing Organisms

Organisms with Chromosomal AmpC

• The American Thoracic Society notes that AmpC β-lactamases are produced by specific Enterobacterales species with chromosomal genes, including Enterobacter spp., Citrobacter freundii, Serratia marcescens, Morganella morganii, and Providencia spp. 1
• Enterobacter species pose the highest risk for treatment failure because they frequently develop high-level constitutive AmpC expression during therapy with third-generation cephalosporins, even when initially susceptible 1

Resistance Pattern

• AmpC producers demonstrate resistance to all penicillins 1
• Carbapenems remain the safest option for severe infections caused by AmpC producers, with cefepime serving as an effective carbapenem-sparing alternative due to its stability against AmpC hydrolysis 2