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Difficulty: HardInfectious Diseases

Match each clinical presentation of infective endocarditis with the most appropriate targeted diagnostic evaluation or therapeutic intervention.

  • A 68-year-old patient is diagnosed with native valve endocarditis. Blood cultures yield a non-enterococcal Group D Streptococcus (Streptococcus gallolyticus).Perform screening colonoscopy to evaluate for occult colorectal malignancy.
  • A 52-year-old patient with a mechanical mitral valve placed three years ago presents with acute endocarditis. Blood cultures rapidly grow methicillin-susceptible Staphylococcus aureus.Administer a combination regimen of intravenous nafcillin, rifampin, and gentamicin.
  • A 74-year-old patient develops subacute endocarditis following a cystoscopy. Blood cultures grow Enterococcus faecalis demonstrating high-level aminoglycoside resistance.Administer a combination regimen of intravenous ampicillin and ceftriaxone.
  • A 45-year-old patient experiencing homelessness presents with severe body louse infestation and culture-negative endocarditis.Obtain specific serological testing for Bartonella quintana.

Answer

Streptococcus gallolyticus pairs with performing a screening colonoscopy. Staphylococcus aureus prosthetic valve endocarditis pairs with nafcillin, rifampin, and gentamicin. Enterococcus faecalis with high-level aminoglycoside resistance pairs with ampicillin and ceftriaxone. Culture-negative endocarditis in a patient with a body louse infestation pairs with obtaining serology for Bartonella quintana.
Each pairing correctly applies current clinical guidelines for infective endocarditis: S. gallolyticus requires colonoscopy due to a high rate of concomitant colon cancer. S. aureus on a prosthetic valve necessitates a three-drug regimen including rifampin for biofilm penetration. HLAR E. faecalis requires ampicillin plus ceftriaxone for dual beta-lactam synergy. B. quintana is the primary suspect in louse-associated culture-negative endocarditis, requiring serological confirmation.

Step-by-Step Solution

1
Identify the underlying pathogen and host risk factors in each clinical vignette.
Pathogens identified are S. gallolyticus, S. aureus (prosthetic valve), E. faecalis (with HLAR), and a culture-negative organism associated with body lice.
Management of infective endocarditis is highly tailored to the specific organism, its resistance profile, and whether native or prosthetic material is involved.
2
Determine the unique complication, diagnostic requirement, or therapeutic adjustment for each pathogen.
S. gallolyticus requires GI workup. Prosthetic S. aureus requires biofilm penetration. HLAR Enterococcus requires non-aminoglycoside synergy. Louse-borne culture-negative endocarditis points to Bartonella.
Standard endocarditis protocols fail if these specific nuances (e.g., biofilms, HLAR, occult malignancy) are not addressed.
3
Match the specific pathogen requirements to the listed interventions.
The pairings logically align the microbiologic and epidemiologic clues with the standard-of-care guidelines.
This confirms mastery of pathogen-specific management pathways in infectious diseases.

Key Concept

Targeted diagnostic and therapeutic management of infective endocarditis based on organism identity, resistance patterns, and host risk factors.
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Topics

Infectious Diseases

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