Background
- Gram-negative bacteria with inducible or derepressable beta-lactamases, primarily AmpC β-lactamase
Organisms
- Serratia species
- Providencia
- Indole-positive Proteus species (e.g. Proteus vulgaris, but not Proteus mirabilis)
- Citrobacter species
- C. koseri does not have an AmpC
- Enterobacter cloacae, and now also Klebsiella aerogenes (previously Enterobacter aerogenes)
Also:
- Hafnia alvei
- Acinetobacter, though not inducible or AmpC (merely very resistant_
- Morganella morganii
- Cronobacter
- Edwardsiella
Management
- For Enterobacter cloacae, Klebsiella aerogenes, and Citrobacter freundii, avoid all penicillins and cephalosporins regardless of susceptibility testing
- Carbapenems still work, as do aminoglycosides
- Cefipime still works when MIC ≤2 mcg/mL
- For Serratia marcescens, Morganella morganii, and Providencia, treat based on susceptibility testing
- Less data for Hafnia alvei, Citrobacter youngae, and Yersinia enterocolitica, but reasonable to treat based on susceptibility testing
Further Reading
- Jones R, Baquero F, Privitera G, Inoue M, Widermann B. Inducible β-lactamase-mediated resistance to third-generation cephalosporins. Clin Microbio Infect. 1997;3(1):S7-S20.
- https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciz173/5369903
