What type of endocarditis is Staphylococcus aureus (S. aureus) usually associated with?

From the Guidelines

Staphylococcus aureus is typically associated with acute bacterial endocarditis, which is a severe and aggressive form of endocarditis that develops rapidly, often causing severe valve destruction, abscess formation, and systemic embolic complications within days to weeks. This type of endocarditis frequently affects previously normal heart valves, unlike subacute endocarditis which tends to involve damaged valves. The infection commonly occurs in intravenous drug users, patients with intravascular devices, and following healthcare-associated bacteremia. S. aureus produces numerous virulence factors including adhesins that facilitate attachment to heart valves, toxins that damage tissue, and enzymes that help evade host defenses.

Key characteristics of acute bacterial endocarditis caused by S. aureus include:

• Rapid development of severe valve destruction and systemic complications
• Frequently affects previously normal heart valves
• Commonly occurs in intravenous drug users, patients with intravascular devices, and following healthcare-associated bacteremia
• Produces numerous virulence factors that facilitate attachment, damage tissue, and evade host defenses

Treatment typically requires 4-6 weeks of intravenous antibiotics, often with a beta-lactam antibiotic (such as oxacillin 2g IV every 4 hours for methicillin-sensitive strains) or vancomycin (15-20mg/kg IV every 8-12 hours for methicillin-resistant strains) 1. Early surgical intervention is frequently necessary due to the destructive nature of the infection, particularly with prosthetic valve involvement, heart failure, or persistent bacteremia despite appropriate antibiotics 1. The most recent and highest quality study, although not directly addressing the question, provides guidance on the management of patients with valvular heart disease, including those with infective endocarditis 1.

From the FDA Drug Label

The 182 patients with bacteremia comprised 121 with complicated S. aureus bacteremia and 61 with uncomplicated S. aureus bacteremia. The definition of right-sided infective endocarditis (RIE) used in the clinical trial was Definite or Possible Endocarditis according to the modified Duke criteria and no echocardiographic evidence of predisposing pathology or active involvement of either the mitral or aortic valve Complicated RIE comprised patients who were not intravenous drug users, had a positive blood culture for MRSA, serum creatinine ≥2.5 mg/dL, or evidence of extrapulmonary sites of infection. Patients who were intravenous drug users, had a positive blood culture for methicillin-susceptible S. aureus (MSSA), had serum creatinine <2. 5 mg/dL, and were without evidence of extrapulmonary sites of infection were considered to have uncomplicated RIE.

Staphylococcus aureus is usually associated with right-sided endocarditis, particularly in intravenous drug users 2.

• Right-sided infective endocarditis (RIE) is defined as Definite or Possible Endocarditis according to the modified Duke criteria and no echocardiographic evidence of predisposing pathology or active involvement of either the mitral or aortic valve.
• Uncomplicated RIE is often seen in intravenous drug users with methicillin-susceptible S. aureus (MSSA).
• Complicated RIE is often seen in patients with methicillin-resistant S. aureus (MRSA), serum creatinine ≥2.5 mg/dL, or evidence of extrapulmonary sites of infection.

From the Research

Type of Endocarditis Associated with Staphylococcus aureus

• Staphylococcus aureus is usually associated with infective endocarditis (IE) 3, 4, 5, 6, 7
• It can cause endocarditis on architecturally normal cardiac valves 4
• The bacterium is a leading cause of bacteremia and endocarditis, with increasing frequency and antibiotic resistance 4, 5, 7
• Distinguishing patients with S. aureus IE from those with uncomplicated SAB is essential but often difficult 4
• Methicillin-resistant and -susceptible Staphylococcus aureus (MRSA/MSSA) infections are a major global health-care problem, and IE is a complicated infection that can occur 5
• Bacteremia and IE are important causes of morbidity and mortality associated with S. aureus infections 7