Description

• An infection of the valvular (primarily) and/or mural (rarely) endocardium
• System(s) affected: cardiovascular, endocrine/metabolic, hematologic/lymphatic, immunologic, pulmonary, renal/urologic, skin/exocrine, neurologic
• Synonym(s): bacterial endocarditis; subacute bacterial endocarditis (SBE); acute bacterial endocarditis (ABE)

Epidemiology

More common in males (range is 3:2 to 9:1). >50% of cases in the United States occur in individuals >60 years of age.

Incidence

• Native valve endocarditis has variable rates of incidence due to changes in definition over the years.
• 1.5–3% incidence 1 year after prosthetic valve replacement; 3–6% 5 years postreplacement
• Increasing incidence of cardiovascular device–related infections due to higher frequency of implantable devices.
• Can be community- or hospital-acquired
• Most commonly affects the mitral valve and aortic valve (increased left-sided pressures and turbulent flow)

Etiology and Pathophysiology

IE is most commonly caused by a nonbacterial thrombus that adheres to an endocardial surface, coupled with a bacterial source sufficient to seed the thrombus. This can occur from direct bacterial invasion or valvular trauma:

• Native valve endocarditis
  • Acute: Staphylococcus aureus; Streptococcus groups A, B, C, G; Streptococcus pneumoniae; Staphylococcus lugdunensis; Enterococcus spp.; Haemophilus influenzae or parainfluenzae; Neisseria gonorrhoeae
  • Subacute: α-hemolytic streptococci, Streptococcus bovis, Enterococcus spp., S. aureus, Staphylococcus epidermidis; HACEK organisms
• Intravenous drug abuse endocarditis (IVDA) (most commonly tricuspid valve): S. aureus, Enterococcus spp.; Pseudomonas aeruginosa, Burkholderia cepacia, other bacilli (gram-negative); Candida spp.
• Prosthetic valve endocarditis
  • Early (≥12 months after valve implantation): S. aureus, S. epidermidis; gram-negative bacilli; Candida spp., Aspergillus spp.
  • Late (>12 months after valve implantation): α-hemolytic streptococci, S. aureus, Enterococcus spp., S. epidermidis, Candida spp., Aspergillus spp.
• Culture-negative endocarditis: 10% of cases; Bartonella quintana (homeless); Brucella spp., fungi, Coxiella burnetii (Q fever), Chlamydia trachomatis, Chlamydophila psittaci, HACEK organisms
• Device-related endocarditis: coagulase-negative staphylococci or S. aureus

Risk Factors

• Injection drug use, IV catheterization, certain malignancies (colon cancer), poor dentition/infection, chronic hemodialysis, age >60 years, male sex
• High risk with:
  • Structural heart disease, prosthetic cardiac valves, valvular disease, implantable devices, total parenteral nutrition
  • Previous IE
  • Congenital heart disease (CHD): unrepaired cyanotic CHD, including palliative shunts and conduits; repaired CHD with prosthetic device during the first 6 months; repaired CHD with residual defects at or near prosthetic site; cardiac transplant with valvulopathy (1)[B]

General Prevention

• Good oral hygiene
• Antibiotic prophylaxis is only recommended in patients with a high risk of adverse outcomes if IE were to occur (1)[B]—(see “Risk Factors”). Administer 30 to 60 minutes prior to the procedure (exception vancomycin which should be administered 120 minutes prior to the procedure).
• Procedures requiring prophylaxis
  • Oral/upper respiratory tract procedures/biopsies: Amoxicillin 2 g PO 30 to 60 minutes before procedure or ampicillin 2 g IV/IM are first-line prophylactic choices. Clindamycin no longer recommended for dental prophylaxis because it is associated with more frequent and severe adverse effects (i.e., Clostridium difficile infection)
  • GI/GU: Only consider coverage for Enterococcus (with penicillin, ampicillin, piperacillin, or vancomycin) for patients with an established infection undergoing procedures (1)[B].
  • Cardiac valvular surgery or placement of prosthetic intracardiac/intravascular materials: perioperative cefazolin 1 to 2 g IV 30 minutes preoperative or vancomycin 15 mg/kg (maximum 1 g) (penicillin-allergic patients) 60 minutes preoperative (1)[B]
  • Skin/soft tissue: incision and drainage of infected tissue; use agents active against skin pathogens (e.g., cefazolin 1 to 2 g IV q8h or vancomycin 15 mg/kg q12h; max 1 g) if penicillin-allergic or if methicillin-resistant S. aureus (MRSA) suspected.

Commonly Associated Conditions

Most patients with IE have preexisting conditions (see high-risk above).