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Difficulty: HardCardiovascular System

A 65-year-old man is evaluated in the hospital on day 4 of admission for infective endocarditis. He initially presented with a 2-week history of fatigue, low-grade fever, and a new holosystolic murmur at the cardiac apex. A transthoracic echocardiogram obtained on admission demonstrated a 1.21.2-cm vegetation on the posterior leaflet of the mitral valve with moderate mitral regurgitation. Empiric therapy with intravenous vancomycin and ceftriaxone was initiated. Today, final blood culture results from admission show growth of *Streptococcus gallolyticus* (formerly *Streptococcus bovis*) in all four bottles. Susceptibility testing confirms the organism is highly susceptible to penicillin (minimum inhibitory concentration ≤0.12\leq 0.12 μ\mu g/mL) and ceftriaxone. The patient is currently afebrile and hemodynamically stable. His renal function is normal, and he has no known drug allergies.

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

  1. A
    Continue vancomycin and ceftriaxone, and schedule a colonoscopy
  2. B
    Discontinue ceftriaxone, continue intravenous vancomycin, and schedule a colonoscopy
  3. Discontinue vancomycin, continue intravenous ceftriaxone, and schedule a colonoscopyAnswer
  4. D
    Continue vancomycin and ceftriaxone, and schedule a comprehensive dental evaluation
  5. E
    Discontinue ceftriaxone, initiate intravenous daptomycin, and schedule a colonoscopy

Answer

The most appropriate next step is to discontinue vancomycin, continue intravenous ceftriaxone monotherapy, and schedule a colonoscopy.
The correct course of action identifies the need to narrow the antibiotic spectrum to targeted therapy while simultaneously recognizing the strong clinical association between Streptococcus gallolyticus (formerly S. bovis) and colorectal cancer. Empiric therapy for native valve endocarditis typically includes vancomycin (to cover MRSA) and ceftriaxone. Once a highly susceptible organism is isolated, principles of antimicrobial stewardship dictate that broad-spectrum agents must be discontinued. Monotherapy with ceftriaxone (or intravenous penicillin G) is standard and appropriate. Furthermore, S. gallolyticus bacteremia is uniquely associated with colonic neoplasia, making a screening colonoscopy a mandatory diagnostic step in this patient's workup.

Step-by-Step Solution

1
Identify the primary diagnosis and the specific causative pathogen.
The patient has native valve infective endocarditis caused by Streptococcus gallolyticus (S. bovis).
Blood cultures and echocardiographic findings confirm the diagnosis according to the modified Duke criteria.
2
Determine the appropriate antimicrobial adjustments based on susceptibility data.
De-escalate from broad-spectrum empiric coverage to targeted therapy by discontinuing vancomycin and continuing ceftriaxone.
The organism is highly susceptible to penicillin and ceftriaxone; maintaining vancomycin violates antibiotic stewardship and poses unnecessary nephrotoxic risk.
3
Identify necessary disease-specific follow-up for this pathogen.
Schedule a screening colonoscopy.
S. gallolyticus bacteremia has a strong, well-established association with colorectal neoplasia and requires gastrointestinal evaluation.

Key Concept

Management of Streptococcus gallolyticus infective endocarditis requires targeted antibiotic de-escalation (such as ceftriaxone monotherapy) and evaluation for occult colorectal malignancy with a colonoscopy.
Estimated Time:1m 30s
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Topics

Cardiovascular System

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