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Difficulty: MediumInfectious Diseases

A 64-year-old man is evaluated on hospital day 4 for ongoing management of vertebral osteomyelitis. He initially presented with severe mid-back pain, fever, and focal spinal tenderness. Magnetic resonance imaging of the thoracic spine at admission demonstrated T8-T9 discitis and adjacent vertebral body osteomyelitis without an epidural abscess. Blood cultures drawn prior to antibiotic administration have now finalized, showing heavy growth of *Streptococcus agalactiae*. Susceptibility testing indicates the organism is sensitive to penicillin, ceftriaxone, cefepime, and vancomycin. He was empirically started on intravenous vancomycin and piperacillin-tazobactam. Currently, his temperature is 37.1°C (98.8°F), blood pressure is 128/82 mmHg, and pulse is 78/min. His back pain has improved, and his neurologic examination remains unremarkable. Which of the following is the most appropriate next step in pharmacotherapy?

  1. Discontinue current agents and initiate intravenous penicillin GAnswer
  2. B
    Discontinue piperacillin-tazobactam and continue intravenous vancomycin
  3. C
    Discontinue vancomycin and continue intravenous piperacillin-tazobactam
  4. D
    Continue the current regimen of intravenous vancomycin and piperacillin-tazobactam
  5. E
    Discontinue current agents and initiate intravenous daptomycin

Answer

Discontinue current agents and initiate intravenous penicillin G
The correct answer involves discontinuing the broad-spectrum empiric regimen and initiating intravenous penicillin G. This patient has vertebral osteomyelitis caused by Streptococcus agalactiae (Group B Strep). Once the pathogen is identified and shown to be highly susceptible to penicillin, the standard of care—and the core principle of antimicrobial stewardship—is to de-escalate therapy to the narrowest effective agent. Intravenous penicillin G (or intravenous ceftriaxone) provides excellent, targeted bactericidal activity without unnecessarily altering gut flora or promoting broad-spectrum resistance. Because this is a deep-seated bone infection, an extended course of intravenous therapy (e.g., 4 to 6 weeks) is required.

Step-by-Step Solution

1
Analyze the patient's clinical status and microbiological data.
The patient has vertebral osteomyelitis caused by Streptococcus agalactiae, which is susceptible to multiple antibiotics including narrow-spectrum options like penicillin.
Establishing the exact pathogen and its sensitivity profile is the prerequisite for tailoring antibiotic therapy.
2
Evaluate the current empiric antibiotic regimen.
The patient is receiving intravenous vancomycin and piperacillin-tazobactam, which is an appropriately broad empiric regimen for suspected severe healthcare-associated or deep-seated infections.
Empiric therapy is designed to cover all likely pathogens until culture data returns.
3
Apply the principles of antibiotic stewardship to optimize therapy.
The regimen must be de-escalated from broad-spectrum coverage to the narrowest effective targeted therapy (intravenous penicillin G).
De-escalation minimizes collateral damage to the microbiome, reduces the development of antimicrobial resistance, and limits drug toxicity.

Key Concept

Antibiotic de-escalation involves transitioning from broad-spectrum empiric therapy to targeted, narrow-spectrum therapy once a pathogen and its susceptibilities are confirmed.
Estimated Time:1m 15s
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Topics

Infectious Diseases

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