Infectious diseases (sepsis, endocarditis) Practice Questions

Q: A 58-year-old man with a prosthetic aortic valve develops fever 8 months after valve replacement. Blood cultures grow Staphylococcus epidermidis resistant to methicillin. Transesophageal echocardiogram shows a 6 mm vegetation on the prosthetic valve with no evidence of abscess or dehiscence. He is hemodynamically stable. Apply the appropriate treatment strategy for this patient.

Vancomycin plus rifampin plus gentamicin for 6 weeks. ***Vancomycin plus rifampin plus gentamicin for 6 weeks*** - For **prosthetic valve endocarditis (PVE)** caused by **methicillin-resistant Staphylococcus epidermidis (MRSE)**, a triple-drug regimen is required to achieve bactericidal synergy and penetrate biofilms. - The guidelines recommend **Vancomycin** (for resistance), **Rifampin** (to eradicate organisms on the prosthetic surface), and **Gentamicin** (for the first 2 weeks to enhance killing). *Immediate surgical valve replacement* - Surgery is reserved for patients with **hemodynamic instability**, **perivalvular abscesses**, heart failure, or exceptionally large (>10 mm) vegetations. - Current management for a stable patient with a **6 mm vegetation** and no dehiscence begins with **aggressive medical therapy** first. *Daptomycin monotherapy for 4 weeks* - Monotherapy is generally discouraged in **PVE** due to the high risk of developing **daptomycin resistance** and the presence of foreign material. - **Daptomycin** lacks the established clinical evidence that the combination of **Vancomycin/Rifampin/Gentamicin** has for prosthetic infections. *Linezolid for 6 weeks* - **Linezolid** is primarily a **bacteriostatic** agent and is generally not used as first-line therapy for serious endovascular infections like PVE. - It lacks the necessary **bactericidal** synergy required for successful eradication of pathogens embedded in **prosthetic valve biofilms**. *Vancomycin for 4 weeks followed by oral suppression* - A **4-week course** is insufficient for **PVE**, which requires at least **6 weeks** of therapy to prevent recurrence. - **Oral suppression** is not the standard of care for acute infective endocarditis where the primary goal remains **complete sterilization** with combination IV therapy.

Q: A 62-year-old woman with a history of rheumatic heart disease presents with fever, night sweats, and fatigue for 3 weeks. Physical examination reveals a new heart murmur and splinter hemorrhages under her fingernails. Blood cultures grow viridans group streptococci. Transthoracic echocardiogram shows a 12 mm vegetation on the mitral valve with moderate regurgitation. What is the most appropriate antibiotic regimen?

Penicillin G or ceftriaxone for 4 weeks. ***Penicillin G or ceftriaxone for 4 weeks*** - **Viridans group streptococci (VGS)** are typically highly susceptible to **penicillin**, making **Penicillin G** or **Ceftriaxone** the first-line therapy for native valve endocarditis. - A **4-week course** of monotherapy is the standard treatment for **native valve endocarditis** caused by penicillin-susceptible strains to ensure complete eradication. *Vancomycin for 6 weeks* - **Vancomycin** is reserved for patients with severe **beta-lactam allergies** or infections caused by **penicillin-resistant** organisms. - It is not the first-line choice for **highly susceptible VGS** as beta-lactams are more bactericidal and have a better safety profile for long-term use. *Penicillin G plus gentamicin for 2 weeks* - A **2-week synergistic regimen** is only considered for **uncomplicated** VGS endocarditis in patients with prompt clinical response and no extracardiac foci. - This patient's **12 mm vegetation** and moderate regurgitation are relative contraindications for the shortened course due to a higher risk of **treatment failure**. *Ceftriaxone plus rifampin for 6 weeks* - **Rifampin** is specifically indicated for **prosthetic valve endocarditis** to penetrate biofilms, particularly in Staphylococcal infections. - It is not indicated for **native valve** endocarditis caused by **viridans group streptococci**. *Daptomycin for 4 weeks* - **Daptomycin** is typically used for **MRSA** or **Vancomycin-resistant enterococci (VRE)** and is not a first-line agent for streptococcal endocarditis. - Use is generally limited to cases where standard therapies like **penicillin** or **vancomycin** cannot be used or have failed.

Question 1

A 58-year-old man with a prosthetic aortic valve develops fever 8 months after valve replacement. Blood cultures grow Staphylococcus epidermidis resistant to methicillin. Transesophageal echocardiogram shows a 6 mm vegetation on the prosthetic valve with no evidence of abscess or dehiscence. He is hemodynamically stable. Apply the appropriate treatment strategy for this patient.

Accepted Answer

Vancomycin plus rifampin plus gentamicin for 6 weeks

Answer

Vancomycin for 4 weeks followed by oral suppression

Answer

Linezolid for 6 weeks

Answer

Daptomycin monotherapy for 4 weeks

Answer

Immediate surgical valve replacement

Question 2

A 62-year-old woman with a history of rheumatic heart disease presents with fever, night sweats, and fatigue for 3 weeks. Physical examination reveals a new heart murmur and splinter hemorrhages under her fingernails. Blood cultures grow viridans group streptococci. Transthoracic echocardiogram shows a 12 mm vegetation on the mitral valve with moderate regurgitation. What is the most appropriate antibiotic regimen?

Accepted Answer

Penicillin G or ceftriaxone for 4 weeks

Answer

Daptomycin for 4 weeks

Answer

Ceftriaxone plus rifampin for 6 weeks

Answer

Vancomycin for 6 weeks

Answer

Penicillin G plus gentamicin for 2 weeks

Question 3

A 45-year-old man presents to the emergency department with fever, chills, and confusion for 2 days. Vital signs show temperature 39.2°C (102.6°F), heart rate 118/min, blood pressure 88/54 mmHg, and respiratory rate 28/min. Laboratory studies show WBC 18,000/mm³, lactate 4.2 mmol/L, and creatinine 2.1 mg/dL (baseline 0.9 mg/dL). Blood cultures are drawn. What is the most appropriate initial management?

Accepted Answer

Administer broad-spectrum antibiotics within 1 hour and start IV fluid resuscitation

Answer

Start corticosteroids and antibiotics simultaneously

Answer

Start vasopressors immediately before fluid resuscitation

Answer

Obtain CT scan of abdomen and pelvis before starting treatment

Answer

Wait for blood culture results before starting antibiotics

Infectious diseases (sepsis, endocarditis) — MCQs

Infectious diseases (sepsis, endocarditis) — MCQs

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