ITE Infectious Disease Management 3 — Questions and Answers
Question 1: A 70-year-old man undergoes hip arthroplasty and develops fever and wound drainage at day 14. Joint aspiration grows MRSA. What is the antibiotic of choice for MRSA prosthetic joint infection?
- Daptomycin 6mg/kg IV daily
- Vancomycin IV dosed to trough 15-20 mcg/mL (Correct answer)
- Linezolid 600mg BID
- Cefazolin 2g IV q8h
Correct answer: Vancomycin IV dosed to trough 15-20 mcg/mL
Vancomycin IV remains the standard of care for MRSA prosthetic joint infections, typically combined with rifampin for biofilm penetration in device-associated infections.
Question 2: A 50-year-old immunocompromised patient presents with fever, pleuritic chest pain, and a pulmonary nodule with halo sign on CT. Galactomannan antigen returns elevated. What is the most appropriate initial antifungal?
- Fluconazole 400mg IV daily
- Voriconazole 6mg/kg IV q12h x 2 doses, then 4mg/kg q12h (Correct answer)
- Liposomal amphotericin B 3mg/kg/day
- Micafungin 150mg IV daily
Correct answer: Voriconazole 6mg/kg IV q12h x 2 doses, then 4mg/kg q12h
Voriconazole is the preferred first-line treatment for invasive pulmonary aspergillosis based on superior efficacy demonstrated in landmark clinical trials.
Question 3: A 28-year-old woman presents with fever, rash on palms and soles, and headache after camping in North Carolina in May. Peripheral smear shows no parasites but thrombocytopenia and hyponatremia are present. What is the treatment?
- Azithromycin 500mg daily
- Doxycycline 100mg BID (Correct answer)
- Ciprofloxacin 500mg BID
- Chloramphenicol 500mg QID
Correct answer: Doxycycline 100mg BID
Rocky Mountain Spotted Fever (Rickettsia rickettsii) is treated empirically with doxycycline 100mg BID, which should not be delayed awaiting confirmatory testing.
Question 4: A 65-year-old man with a mechanical aortic valve develops fever, positive blood cultures for viridans streptococcus, and a new perivalvular abscess on TEE. What does the abscess finding indicate?
- Outpatient antibiotic therapy is sufficient
- Empiric switch to vancomycin is required
- Cardiac surgery consultation is required (Correct answer)
- Repeat TEE in 2 weeks is the next step
Correct answer: Cardiac surgery consultation is required
Perivalvular abscess is a class I indication for urgent cardiac surgery in prosthetic valve endocarditis, as medical therapy alone is insufficient.
Question 5: A 45-year-old HIV-positive man (CD4 180, not on ART) is diagnosed with PCP pneumonia. His PaO2 on room air is 58 mmHg. In addition to TMP-SMX, what adjunctive therapy should be started?
- Inhaled pentamidine
- Systemic corticosteroids (prednisone 40mg BID) (Correct answer)
- Adjunctive atovaquone
- G-CSF support
Correct answer: Systemic corticosteroids (prednisone 40mg BID)
Adjunctive corticosteroids are indicated for PCP when PaO2 < 70 mmHg or A-a gradient > 35 mmHg, as they reduce mortality by preventing inflammatory deterioration.
Question 6: A 22-year-old college student presents with fever, pharyngitis, cervical lymphadenopathy, and splenomegaly. Heterophile antibody test is positive. Which complication requires activity restriction?
- Thrombocytopenia
- Splenic rupture risk (Correct answer)
- Airway obstruction
- Hepatitis
Correct answer: Splenic rupture risk
Splenic rupture is a rare but life-threatening complication of infectious mononucleosis; patients should avoid contact sports and strenuous activity for at least 3-4 weeks.
Question 7: A 55-year-old diabetic woman presents with right facial pain, black eschar on the palate, and periorbital edema. CT shows sinus involvement extending to the orbit. What is the likely pathogen?
- Aspergillus fumigatus
- Mucor/Rhizopus species (Correct answer)
- Candida albicans
- Fusarium solani
Correct answer: Mucor/Rhizopus species
Rhinocerebral mucormycosis caused by Mucorales (Mucor/Rhizopus) classically occurs in diabetic ketoacidosis, presenting with black necrotic eschar and rapid orbital/CNS spread.
ITE Infectious Disease Management 3
A 70-year-old man undergoes hip arthroplasty and develops fever and wound drainage at day 14.
Joint aspiration grows MRSA.
What is the antibiotic of choice for MRSA prosthetic joint infection?