Is cefepime an acceptable alternative to carbapenems in the treatment of cefepime susceptible extended spectrum beta-lactamase (ESBL) Gram-negatives?

Irrespective of in-vitro susceptibility results, cefepime should be avoided in the treatment of serious ESBL infections associated with bacteremia, pneumonia, intraabdominal infection, endocarditis, bone/joint infection or whenever a high bacterial inoculum is suspected. Cefepime should be considered only in non-severe infections (eg, uncomplicated urinary tract infection) when the minimum inhibitory concentration (MIC) is 2 mg/L or less (1).


To date, clinical studies comparing cefepime vs carbapenem have been small and/or retrospective, often with conflicting results (1). A 2016 propensity score-matched study of patients with ESBL bacteremia receiving cefepime therapy followed by carbapenem therapy vs carbapenem for the entire treatment duration found higher 14 day mortality in the cefepime group (41% vs 20% in the carbapenem group) (2).  Of note, 2 of the patients receiving cefepime who died were infected with an ESBL organism with MIC of 1 mcg/mL. 


Another study found cefepime to be inferior to carbapenem therapy in ESBL bacteremic patients with better outcome when cefepime MIC was 1 ug/m or less (3).


Two studies involving patients with ESBL UTIs found no significant difference between cefepime and carbapenem in clinical and microbiological response or in-hospital mortality, while another UTI study with a high rate of septic shock (33%) found that cefepime was inferior to carbapenem in clinical and microbiological response (2).


The diminished efficacy of cefepime for the treatment of ESBL infections may be related to its “inoculum effect” ie, marked increase in MIC with increased inoculum size compared to that used in standard laboratory susceptibility testing (1,4).   


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  1. Karaiskos I, Giamarellou H. Carbapenem-sparing strategies for ESBL producers: when and how. Antibiotics 2020;9,61.
  2. Wang R, Cosgrove S, Tschudin-Sutter S, et al. Cefepime therapy for cefepime-susceptible extended-spectrum beta-lactamase-producing Enerobacteriaceae bacteremia. Open Forum Infect Dis 2016.
  3. Lee NY, Lee CC, Huang WH, et al. Cefepime therapy for monomicrobial bacteremia caused by cefepime-susceptible extended-spectrum beta-lactamase-producing Enterobacteriaceae: MIC matters. Clin Infect Dis 203;56:488-95.
  4. Smith KP, Kirby JE. The inoculum effect in the era of multidrug resistance:minor differences in inoculum have dramatic effect on MIC determination. Antimicrob Agents Chemother 2018;62:e00433-18.

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Is cefepime an acceptable alternative to carbapenems in the treatment of cefepime susceptible extended spectrum beta-lactamase (ESBL) Gram-negatives?

Is meropenem a good choice of antibiotic for treatment of my patient’s intraabdominal infection involving enterococci?

Although meropenem is a broad spectrum antibiotic that covers many gram-negative and gram-positive organisms as well as anaerobes, its activity against enterococci is generally poor and leaves much to be desired.

In a study of ampicillin-sensitive E. faecalis isolates from hospitalized patients, only 36% of isolates were considered susceptible (MIC≤4 mg/L); activity against E. faecium isolates was similarly poor.1 Several other studies have reported the suboptimal activity of meropenem against both E. faecalis and E. faecium, 2-4 with susceptibility rates as low as 8.6% depending on the MIC break point used.3

A popular textbook and a handbook on infectious diseases also do not recommend the use of meropenem for treatment of enterococcal infections. 5,6

Of interest, the package insert states that meropenem is indicated for complicated skin and soft tissue infections due to a variety of organisms, including E. faecalis (vancomycin-susceptible isolates only), but not for complicated intra-abdominal infections or meningitis due this organism.7

In our patient with intraabdominal infection,  we may consider piperacillin-tazobactam instead.  Piperacillin-tazobactam is a broad spectrum antibiotic with excellent coverage against anaerobes and ampicillin-susceptible E. faecalis.1,8  



  1. Endtz HP, van Dijk WC, Verbrugh HA, et al. Comparative in-vitro activity of meropenem against selected pathogens from hospitalized patients in the Netherlands. J Antimicrob Chemother 1997;39:149-56.
  2. Pfaller MA, Jones RN. A review of the in vitro activity of meropenem and comparative antimicrobial agents tested against 30,254 aerobic and anaerobic pathogens isolated world wide. Diag Microbiol Infect Dis 1997;28:157-63.
  3. Hallgren A, Abednazari H, Ekdahl C, et al. Antimicrobial susceptibility patterns of enterococci in intensive care units in Sweden evaluated by different MIC breakpoint systems. J Antimicrob Chemother 2001;48:53-62.
  4. Hoban DJ, Jones RN, Yamane N, et al. In vitro activity of three carbapenem antibiotics comparative studies with biapenem (L-627), imipenem, and meropenem against aerobic pathogens isolated worldwide. Diag Microbiol Infect Dis 993;17:299-305.
  5. Chambers HF. Carbapenem and monobactams. In Mandell GL et al. eds. Principles and practice of infectious diseases. 2010, pp 341-45.
  6. Cunha CB, Cunha BA. Antibiotic essentials. 2017, pp 689-91.
  7. Meropenem.
  8. Perry CM, Markham A. Piperacillin/tazobactam. Drugs 1999;57:805-43.

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Is meropenem a good choice of antibiotic for treatment of my patient’s intraabdominal infection involving enterococci?