AmpC B-Lactamase-Producing Enterobacterales

AmpC B-Lactamase-Producing Enterobacterales


General Information

Cefepime (when MIC </=2 mcg/mL)

  • Meropenem (should be considered first-line when cefepime MIC >/=4 mcg/mL)
  • Ciprofloxacin
  • Cystitis: nitrofurantoin, aminoglycosides

“HECK-YES” Organisms: 

  • Hafnia alvei
  • Enterobacter cloacae
  • Citrobacter freundii, youngae
  • Klebsiella (Enterobacter) aerogenes
  • Yersenia enterocolitica

Organisms historically presumed to be at risk for the development of clinically significant ampC expression, such as Serratia marcescens, Morganella morganii, and Providencia species, are unlikely to overexpress ampC. When S. marcescens, M. morganii, or Providencia spp. are recovered from clinical cultures, the panel suggests selecting antibiotic treatment according to susceptibility testing results (e.g., administer ceftriaxone if susceptible to ceftriaxone).

See individual organisms

  • ESBLs vs. AmpC: Most ESBLs are plasmid-encoded, whereas AmpCs are usually inducible and chromosomal
  • In the lab, AmpCs demonstrate resistance to cefoxitin and cefotetan