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Difficulty: HardInfectious Diseases

A 48-year-old woman is hospitalized in the hematology-oncology unit undergoing induction chemotherapy for acute myeloid leukemia. On hospital day 12, she develops chills and a new-onset fever. Her temperature is 38.7°C (101.7°F), blood pressure is 110/68 mm Hg, and pulse is 112/min. Physical examination reveals a clean central venous catheter insertion site and no focal signs of infection. Her absolute neutrophil count is 100/mm³. Two sets of blood cultures are obtained, and empiric therapy with intravenous cefepime is initiated. Forty-eight hours later, the patient is alert and her temperature has normalized to 37.2°C (99.0°F). Her vital signs are stable, and her absolute neutrophil count is now 150/mm³. The initial blood cultures are finalized, showing growth of Klebsiella pneumoniae in both sets. Susceptibility testing demonstrates that the isolate is sensitive to ceftriaxone, cefepime, piperacillin-tazobactam, and meropenem, but resistant to ampicillin.

Which of the following is the most appropriate next step in antimicrobial management?

  1. Continue intravenous cefepimeAnswer
  2. B
    Transition to intravenous ceftriaxone
  3. C
    Transition to intravenous piperacillin-tazobactam
  4. D
    Add intravenous vancomycin to the current regimen
  5. E
    Add intravenous gentamicin to the current regimen

Answer

Continue intravenous cefepime
The most appropriate next step is to continue intravenous cefepime. This patient has febrile neutropenia, a medical emergency defined by a fever in the setting of an absolute neutrophil count (ANC) below 500/mm³. The standard initial management is empiric monotherapy with an anti-pseudomonal beta-lactam (e.g., cefepime, meropenem, or piperacillin-tazobactam). When a specific pathogen is identified, antimicrobial therapy must ensure coverage for that organism. However, a critical exception to standard antibiotic stewardship rules applies here: broad-spectrum anti-pseudomonal coverage MUST be maintained until the neutropenia resolves (typically defined as an ANC > 500/mm³), regardless of the specific pathogen isolated. In this case, the Klebsiella pneumoniae isolate is fully susceptible to the empiric cefepime. Because cefepime effectively treats the identified pathogen while maintaining the mandatory prophylactic shield against Pseudomonas aeruginosa during the patient's ongoing profound neutropenia (ANC 150/mm³), continuing the current regimen is correct.

Step-by-Step Solution

1
Identify the primary clinical condition.
The patient has febrile neutropenia (fever + absolute neutrophil count < 500/mm³) secondary to cytotoxic chemotherapy.
Establishing the immune status of the host dictates the empiric and definitive antibiotic treatment pathways, which differ significantly from immunocompetent hosts.
2
Evaluate the clinical trajectory and culture results.
The patient has clinically stabilized (afebrile, normal vitals) on empiric intravenous cefepime. Cultures isolated Klebsiella pneumoniae, which is susceptible to cefepime as well as narrower-spectrum agents like ceftriaxone.
This confirms that the current empiric therapy is successfully treating the primary bacteremia.
3
Apply the rule for targeted therapy in neutropenic patients.
Determine that de-escalating to ceftriaxone is unsafe, and continuing cefepime is required.
In profound neutropenia, broad-spectrum anti-pseudomonal coverage (provided by cefepime) MUST be maintained until the neutropenia resolves (ANC > 500/mm³), even if a non-pseudomonal organism is identified. Ceftriaxone lacks this required anti-pseudomonal activity.

Key Concept

In patients with neutropenic fever, targeted therapy must be provided for any isolated pathogens, but broad-spectrum anti-pseudomonal coverage must be maintained until the absolute neutrophil count recovers to greater than 500/mm³.
Estimated Time:1m 30s
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Infectious Diseases

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