A 35-year-old man with a history of intravenous drug use presents with 3 weeks of fever, pleuritic chest pain, and multiple nodular infiltrates on chest X-ray. On examination, a holosystolic murmur is heard at the left lower sternal border that increases with inspiration. Blood cultures are most likely to grow which organism?

• A Streptococcus viridans
• B Staphylococcus aureus ✓
• C Enterococcus faecalis
• D Pseudomonas aeruginosa

Explanation

Right-sided endocarditis in IV drug users most commonly affects the tricuspid valve. The holosystolic murmur increasing with inspiration is Carvallo's sign, characteristic of tricuspid regurgitation. Septic pulmonary emboli cause the nodular infiltrates and pleuritic pain. S. aureus is the causative organism in the majority of IV drug use-associated endocarditis cases.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.