American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the first-line empiric therapy for patients with ventilator-associated pneumonia suspected to be caused by extended-spectrum β-lactamase-producing Enterobacteriaceae?

1. Vancomycin

2. Carbapenems, such as meropenem

3. Piperacillin-tazobactam

4. Ciprofloxacin

The correct answer is: Carbapenems, such as meropenem

In the context of ventilator-associated pneumonia (VAP) caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, the first-line empiric therapy is carbapenems, such as meropenem. This choice is based on the efficacy of carbapenems against ESBL-producing organisms, which have a resistance mechanism that renders many beta-lactam antibiotics ineffective. Carbapenems are broad-spectrum antimicrobials that maintain activity against most Gram-negative bacilli, including those that produce ESBLs. Given their pharmacodynamics and low resistance rates among ESBL-producing bacteria, they are preferred in severe infections like VAP to ensure adequate coverage. Other alternatives, including Piperacillin-tazobactam, do not provide reliable coverage for ESBL-producing strains, while Vancomycin primarily targets Gram-positive bacteria and would not adequately address the suspected pathogens. Ciprofloxacin, a fluoroquinolone, may also be less effective due to potential resistance issues and would not cover all ESBL-producing organisms adequately. Therefore, carbapenems, such as meropenem, represent the most appropriate and effective choice for empiric therapy under these circumstances.