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Difficulty: Very hardInfectious Diseases

Match the following complex clinical scenarios and isolated pathogens with the most appropriate, definitive targeted antimicrobial therapy.

  • A 55-year-old man with a prosthetic mitral valve develops endocarditis. Blood cultures grow Enterococcus faecalis susceptible to ampicillin but exhibiting high-level resistance to gentamicin.Intravenous ampicillin and intravenous ceftriaxone
  • A 62-year-old woman in the intensive care unit with a central venous catheter develops septic shock. Blood cultures grow Candida auris.Intravenous echinocandin (e.g., micafungin)
  • A 45-year-old man from an endemic region presents with chronic fever, weight loss, and massive splenomegaly. Bone marrow aspiration reveals intracellular amastigotes within macrophages.Intravenous liposomal amphotericin B
  • A 38-year-old man with a history of intravenous drug use has right-sided endocarditis. Blood cultures grow methicillin-resistant Staphylococcus aureus with a vancomycin minimum inhibitory concentration (MIC) of 4 mcg/mL.Intravenous daptomycin
  • A 28-year-old woman with a history of IgE-mediated anaphylaxis to penicillin presents with secondary syphilis at 14 weeks gestation.Inpatient penicillin desensitization followed by penicillin G

Answer

The correct pairings match Enterococcus faecalis with HLAR to ampicillin and ceftriaxone; Candida auris to an echinocandin; visceral leishmaniasis to liposomal amphotericin B; VISA endocarditis to daptomycin; and pregnant syphilis patients with penicillin allergy to penicillin desensitization and therapy.
Each scenario tests a specific, high-level exception or requirement in infectious disease management. 1) E. faecalis with high-level aminoglycoside resistance requires ampicillin plus ceftriaxone for synergy. 2) Candida auris requires echinocandins due to prevalent multidrug resistance. 3) Visceral leishmaniasis is definitively treated with liposomal amphotericin B. 4) Vancomycin-intermediate S. aureus (VISA) requires a switch to an agent like daptomycin. 5) Pregnant patients with syphilis must receive penicillin, requiring formal desensitization if allergic.

Step-by-Step Solution

1
Analyze the Enterococcus faecalis scenario.
Identify the need for ampicillin and ceftriaxone.
High-level resistance to gentamicin precludes its use for synergy; ceftriaxone provides an alternative synergistic mechanism with ampicillin.
2
Evaluate the Candida auris bloodstream infection.
Select an echinocandin (e.g., micafungin).
C. auris has high rates of resistance to azoles, making echinocandins the initial treatment of choice per CDC guidelines.
3
Diagnose the parasitic infection causing massive splenomegaly.
Identify visceral leishmaniasis requiring liposomal amphotericin B.
Amastigotes within macrophages confirm the diagnosis, and liposomal amphotericin B is the first-line therapy.
4
Assess the treatment for MRSA with an elevated vancomycin MIC.
Choose intravenous daptomycin.
An MIC of 4 mcg/mL defines VISA, requiring a switch to a different bactericidal agent like daptomycin.
5
Determine the syphilis treatment for a pregnant, penicillin-allergic patient.
Opt for penicillin desensitization followed by penicillin G.
Penicillin is the only agent proven to effectively treat maternal infection and prevent congenital syphilis; desensitization is mandatory.

Key Concept

Targeted antimicrobial therapy for highly resistant pathogens and special populations
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Topics

Infectious Diseases

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