Infective endocarditis

Etiology

Native valve (non-IVDU)

• Viridans streptococci (60%)
• Staphylococcus aureus (20%)
• Enterococci (5-10%)
• Less common:
  • Other streptococci, eg, Streptococcus pneumoniae; group A Streptococcus; groups B, C, and G streptococci
  • HACEK organisms (gram-negative): Haemophilus aphrophilus, Haemophilus parainfluenzae, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae
  • Fungi

IVDU with native valve

• Staphylococcus aureus (60%)
• Enterococci
• Streptococci
• Gram-negative rods, eg, Pseudomonas, Serratia
• Fungi, eg, Candida

Prosthetic valve

• Early (< 2 months): Staphylococcus aureus, coagulase-negative Staphylococcus, gram-negatives, fungi
• Late (>2 months): Like native valve plus coagulase-negative Staphylococcus

"Culture negative" endocarditis

• Fungi
• Q fever
• Legionella
• Psittacosis
• Bartonella
• Nutritionally deficient streptococci
• Brucella
• HACEK organisms
• Anaerobes