Staphylococcus aureus Most Commonly Causes Cardiac Abscesses
Staphylococcus aureus is the predominant organism causing cardiac abscesses, including intracardiac abscesses associated with infective endocarditis. This pathogen has emerged as the most common cause of acute bacterial endocarditis and is specifically identified in the Duke criteria as the organism demonstrated in intracardiac abscesses 1.
Primary Causative Organism
S. aureus is now the most common cause of infective endocarditis in most industrialized countries, having surpassed viridans group streptococci, and is definitively the most common agent of acute (rapidly progressive) bacterial endocarditis 1.
The American Heart Association specifically identifies S. aureus as the organism demonstrated by culture or histology in intracardiac abscesses as part of the pathological criteria for definite infective endocarditis 1.
S. aureus causes aggressive disease with mortality rates of 25-40% in left-sided endocarditis, significantly higher than other organisms, reflecting its virulent nature and propensity for complications including abscess formation 2.
Clinical Context and Risk Factors
Healthcare-associated exposures are the primary route for S. aureus cardiac infections in non-drug users, particularly:
- Chronic hemodialysis 2
- Intravascular catheters and devices (central venous catheters, pacemaker leads) 2
- Diabetes mellitus 2
- Recent hospitalization or invasive procedures within 30 days 2
S. aureus has unique virulence properties that enable it to cause endocarditis and abscess formation on architecturally normal cardiac valves, unlike most other organisms that require pre-existing valve damage 3.
Secondary Consideration: Coagulase-Negative Staphylococci
While S. aureus dominates, coagulase-negative staphylococci (particularly S. epidermidis) are important in specific contexts:
Most common cause of early prosthetic valve endocarditis (within 60 days of surgery), where organisms are implanted at the time of surgery 1, 4, 5.
Associated with indwelling vascular catheters and prosthetic material 1.
Account for only about 5% of native valve endocarditis cases 5.
Clinical Implications
Any S. aureus bacteremia warrants echocardiography given the high frequency and virulence of subsequent endocarditis and potential abscess formation 2.
Myocardial abscess can occur even without documented endocarditis in the setting of S. aureus bacteremia, particularly in hemodialysis patients with infected vascular access 6.
Intracardiac abscesses represent a major complication requiring consideration of surgical intervention, as medical therapy alone often fails in the presence of abscess formation 7.