AmpC and extended-spectrum beta-lactamases

Chambers, 2023Infectious Diseases Society of America (IDSA), 2023Paul, 2022

Some Enterobacterales are intrinsic producers of AmpC beta-lactamases, although the amount they produce can vary. Bacteria that are more likely to produce clinically significant amounts of AmpC beta-lactamases1 are generally resistant to penicillins and cephalosporins. Carbapenems and some cephalosporins (eg cefepime) retain clinical activity against bacteria that produce AmpC enzymes. These bacteria will often be susceptible to other drug classes, including quinolones (eg ciprofloxacin) and aminoglycosides. The empirical antibiotic regimens recommended in these guidelines for clinical syndromes likely to be caused by AmpC-producing bacteria (eg arthroplasty device infection) are appropriate for isolates that produce these enzymes. If the appropriateness of a regimen is uncertain, seek advice from an infectious diseases physician or clinical microbiologist.

Bacteria that produce extended-spectrum beta-lactamases (ESBLs) are usually susceptible to carbapenems and may be susceptible in vitro to other beta lactams. Treatment regimens are given in the clinical topics when ESBL-producing bacteria are an important cause of infection.

1 Bacteria at high risk of clinically significant AmpC beta-lactamase production include Hafnia alvei, Enterobacter cloacae complex, Citrobacter freundii, Klebsiella aerogenes and Yersinia enterocolitica. Other members of the group previously known as ESCAPPM (eg Serratia species, Providencia species) are less likely to have clinically significant AmpC production and may still be suitable for treatment with cephalosporins if they test susceptible – seek expert advice from an infectious diseases physician or clinical microbiologist.Return