Review Question - QID 104903

This patient's history of IV and IM drug use places him at risk for bacterial endocarditis, the most likely etiology for his presenting symptoms. Initial treatment with IV vancomycin and IV ceftriaxone in this situation should target MRSA, streptococci, and enterococci.

The common causative pathogens for bacterial endocarditis in patients who use IV drugs include MRSA, streptococci, and enterococci. Initial antibiotics, assuming native cardiac valves, includes vancomycin to treat MRSA and enterococci as well as ceftriaxone to treat streptococci species. Treatment should not be delayed to obtain an echocardiogram. The patient's systolic murmur suggests the possibility of tricuspid valve disease, which is more common in patients who use IV drugs.

Pierce et al. review the diagnosis and management of bacterial endocarditis. In the initial management, they recommend obtaining a baseline ECG, especially looking for 1) evidence of conduction delay that could suggest involvement beyond just the heart valves and 2) evidence of myocardial ischemia, a feared complication of endocarditis. Strong indications for surgical evaluation include valve dehiscence, perforation, or rupture and large perivalvular abscess. Finally, rifampin is indicated in patients with prosthetic valve endocarditis.

Omari et al. describe a retrospective case series at their institution, seeking to identify those patients at high risk for abscess formation, one of the feared complications of bacterial endocarditis. Notably, IV drug use was found to be one of these risk factors, and abscess formation should be monitored clinically (e.g. evidence of heart failure, worsening valve function, persistent fevers or signs of infection) and by serial ECG in the inpatient setting.

Illustration A is an echocardiogram image of a patient with tricuspid valve endocarditis. Transesophageal echocardiogram has been found to be more sensitive than transthoracic echocardiogram for the diagnosis of bacterial endocarditis but is not always indicated.

Incorrect Answers:
Answer 1: IV vancomycin alone would not provide adequate coverage of streptococcal species.
Answer 2: IV levofloxacin historically would have provided coverage of streptococcal species, but resistance levels are currently high enough that other agents should be chosen.
Answer 4: This regimen, including IV gentamycin and PO rifampin, is indicated in endocarditis involving prosthetic valves.
Answer 5: Although fungal, especially candidal, endocarditis can occur, azoles are not indicated as part of empiric therapy unless specific suspicion exists.