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Difficulty: MediumInfectious Diseases

A 54-year-old man is evaluated in the intensive care unit for a new-onset fever. He was admitted 6 days ago following a severe motor vehicle collision that resulted in multiple rib fractures and a pulmonary contusion. He required endotracheal intubation and mechanical ventilation on the day of admission. Over the past 24 hours, he has developed a temperature of 38.9∘C38.9^\circ\text{C} (102.0∘F102.0^\circ\text{F}) and requires an increasing fraction of inspired oxygen (FiO2\text{FiO}_2) and positive end-expiratory pressure. Endotracheal suctioning yields thick, purulent secretions. A chest radiograph reveals a new right lower lobe consolidation. His leukocyte count is 16,500/mm316,500/\text{mm}^3. A bronchoalveolar lavage is performed, and he is started on empiric intravenous vancomycin and cefepime. Two days later, his oxygenation has stabilized. The bronchoalveolar lavage fluid cultures grow >104 CFU/mL> 10^4 \text{ CFU/mL} of *Pseudomonas aeruginosa*. The isolate is susceptible to cefepime, piperacillin-tazobactam, and meropenem. No other organisms are isolated. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

  1. Discontinue vancomycin and continue intravenous cefepimeAnswer
  2. B
    Continue intravenous vancomycin and cefepime
  3. C
    Discontinue vancomycin and replace cefepime with intravenous meropenem
  4. D
    Discontinue vancomycin and add intravenous ciprofloxacin to the current regimen
  5. E
    Transition to intravenous piperacillin-tazobactam and linezolid

Answer

Discontinue vancomycin and continue intravenous cefepime.
The correct response demonstrates appropriate antibiotic stewardship by de-escalating empiric broad-spectrum therapy once culture data are available. The patient has ventilator-associated pneumonia (VAP) and was started on empiric vancomycin (for MRSA) and cefepime (for Pseudomonas and other Gram-negatives). Bronchoalveolar lavage cultures definitively isolated *Pseudomonas aeruginosa* susceptible to cefepime, without any growth of MRSA. Therefore, vancomycin should be discontinued to reduce the risk of adverse effects (e.g., acute kidney injury), and cefepime should be continued as targeted, single-agent therapy.

Step-by-Step Solution

1
Evaluate the clinical presentation and initial management.
The patient developed ventilator-associated pneumonia (VAP) and was appropriately started on empiric broad-spectrum coverage for MRSA (vancomycin) and antipseudomonal beta-lactam (cefepime).
Empiric VAP therapy must cover the most common, high-risk nosocomial pathogens based on local antibiograms and patient risk factors.
2
Analyze the culture and susceptibility data.
Cultures grew only *Pseudomonas aeruginosa*, which is fully susceptible to the currently administered cefepime. Notably, no MRSA or other Gram-positive pathogens were isolated.
Definitive antibiotic therapy relies on pathogen identification and susceptibility testing to optimize efficacy and minimize collateral damage.
3
Apply the principles of antibiotic stewardship to modify therapy.
Vancomycin should be discontinued to eliminate unnecessary MRSA coverage, and cefepime can be continued as targeted monotherapy.
De-escalation of empiric broad-spectrum antibiotics to narrower, targeted agents prevents the development of multidrug-resistant organisms and reduces medication-related adverse effects (such as vancomycin-induced acute kidney injury).

Key Concept

In the management of ventilator-associated pneumonia (VAP), empiric broad-spectrum antibiotics should be de-escalated to targeted monotherapy as soon as culture and susceptibility results are available and demonstrate a susceptible pathogen.
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Infectious Diseases

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