Extended-Spectrum Beta-Lactamases

Wise words from Mark Crislip, MD, an infectious disease doc and creator of the Infectious Disease Compendium, hands down the most entertaining medical app out there:

Regarding ESBL-producing organisms like E. coli and Klebsiella spp.:

Be wary. ESBL (extended spectrum beta lactamase that hydrolyse most beta-lactams (sparing only cephamycins and carbapenems) carrying E. coli is are increasing in frequency and the only reliable antibiotic are carbapenems, including ertapenem (PubMed). Risks for ESBL include health care, urinary catheters and prior antibiotics and if you choose wrong there is increased mortality (PubMed).  If the MIC for an ESBL to piperacillin/tazobactam is <= 2 the patient will do fine but if higher MICs expect death (PubMed). For bacteremia (or suspected) from and ESBL, carbepenem s have less mortality than piperacillin/tazobactam (PubMed).

If the organism is an ESBL, DO NOT use cefepime even if susceptible. Won’t work as well as carbapenems (PubMed). Remember that sensitive in the lab does not always mean effective in the patient.

A post analysis (PubMed) suggests the beta lactamase inhibitor combinations (if MIC < 2) are better than carbapenems for treating ESBL producing E. coli (PubMed), but, as the Xigris debacle reminds us, post hoc analysis are often crap and not to be believed.


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