Match each clinical vignette describing an immunocompromised patient with an infectious di… — USMLE Step 2 CK

Match each clinical vignette describing an immunocompromised patient with an infectious disease to the most appropriate targeted antimicrobial therapy, taking into account patient-specific contraindications.

A $45$ -year-old man with acute myeloid leukemia and profound neutropenia develops fever, pleuritic chest pain, and hemoptysis. Chest CT shows a dense consolidation with a halo sign. Serum galactomannan is markedly elevated. Baseline ECG reveals a QTc interval of $560$ msec.Intravenous isavuconazole
A $38$ -year-old man with untreated HIV presents with severe hypoxemia ( $PaO_2$ $55$ mmHg on room air) and bilateral interstitial infiltrates. Induced sputum is positive for Pneumocystis jirovecii. He has a known history of severe glucose-6-phosphate dehydrogenase (G6PD) deficiency.Intravenous pentamidine and adjunctive corticosteroids
A $65$ -year-old woman with recurrent UTIs presents with septic shock. Blood cultures grow Extended-Spectrum Beta-Lactamase (ESBL)-producing Escherichia coli resistant to fluoroquinolones. She has a documented history of IgE-mediated anaphylaxis to all penicillins, cephalosporins, and carbapenems.Intravenous amikacin
A $50$ -year-old renal transplant recipient presents with decreased visual acuity. Fundoscopy reveals perivascular retinal exudates with hemorrhage. Complete blood count shows a leukocyte count of $1,200/\text{mm}^3$ and absolute neutrophil count of $400/\text{mm}^3$ .Intravenous foscarnet

Answer

Each scenario requires bypassing the standard first-line antimicrobial agent due to a critical, patient-specific contraindication: use isavuconazole to avoid QTc prolongation in aspergillosis, pentamidine to avoid hemolysis in G6PD-deficient severe PCP, amikacin to avoid beta-lactam anaphylaxis in ESBL bacteremia, and foscarnet to avoid worsening neutropenia in CMV retinitis.

Correct matching relies on synthesizing the infectious diagnosis with critical pharmacological contraindications to select the single best alternative therapy.

Step-by-Step Solution

Evaluate the first vignette for diagnosis and contraindications.

Diagnosis: Invasive Aspergillosis. Contraindication: QTc 560 msec.

Voriconazole is standard but prolongs QTc. Isavuconazole must be selected because it uniquely shortens the QTc interval.

Evaluate the second vignette for severity, diagnosis, and contraindications.

Diagnosis: Severe Pneumocystis jirovecii pneumonia (PaO2 < 70 mmHg requires steroids). Contraindication: G6PD deficiency.

TMP-SMX, Dapsone, and Primaquine induce oxidative stress and hemolysis in G6PD deficiency. IV pentamidine is required for severe disease.

Evaluate the third vignette for resistance patterns and allergies.

Diagnosis: ESBL E. coli bacteremia. Contraindication: Anaphylaxis to all beta-lactams.

Carbapenems are standard for ESBL, but the anaphylaxis history precludes their use. Aminoglycosides (Amikacin) offer non-beta-lactam bactericidal coverage.

Evaluate the fourth vignette for viral etiology and drug toxicities.

Diagnosis: CMV retinitis. Contraindication: Pre-existing severe neutropenia (ANC 400).

Ganciclovir causes dose-dependent bone marrow suppression. Foscarnet treats CMV effectively while avoiding further myelosuppression.

Key Concept

Antimicrobial Stewardship and High-Yield Drug Contraindications

Estimated Time:3m 0s

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