A 59-year-old woman is evaluated in the hospital on day 3 of admission for acute cholangitis. She initially presented with fever, right upper quadrant pain, and jaundice. She underwent an uncomplicated endoscopic retrograde cholangiopancreatography (ERCP) with stone extraction on the day of admission and was started on empiric piperacillin-tazobactam and vancomycin. She is currently afebrile and her hemodynamics are stable.
Blood cultures drawn on admission are now positive for *Klebsiella aerogenes*. Antimicrobial susceptibility testing is reported as follows:
| Antimicrobial Agent | Result |
|---|---|
| Ampicillin | Resistant |
| Cefazolin | Resistant |
| Ceftriaxone | Susceptible |
| Ceftazidime | Susceptible |
| Cefepime | Susceptible |
| Piperacillin-tazobactam | Susceptible |
| Meropenem | Susceptible |
Which of the following is the most appropriate definitive pharmacotherapy for this patient?
- CefepimeCevap
- BCeftriaxone
- CMeropenem
- DPiperacillin-tazobactam
- EAmpicillin-sulbactam
Cevap
Cefepime is the most appropriate definitive therapy for this infection.
Cefepime is the correct answer because it is a fourth-generation cephalosporin that is highly stable against hydrolysis by AmpC beta-lactamases. Current infectious disease guidelines recommend cefepime as the definitive therapy of choice for invasive infections caused by moderate-to-high risk AmpC producers (such as Klebsiella aerogenes, Enterobacter cloacae, and Citrobacter freundii) when the isolate demonstrates in vitro susceptibility. This approach effectively treats the infection while sparing carbapenems.
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Treatment of invasive AmpC-producing Enterobacterales (e.g., Klebsiella aerogenes, Enterobacter cloacae) requires cefepime or a carbapenem; third-generation cephalosporins must be avoided due to the high risk of inducible resistance.
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