Causes

• Streptococcus viridans - Streptococcus mitis/ sanguinis / oralis/ sorbrinus/ milleri

  • most common cause - 40-50%
  • follow dental procedures that invlove manipulation of gingival tissue or perforation of oral mucosa,
  • procedures involving incision & biopsy of respiratory tract

• Staphylococcus epidermidis

  • IE transmitted via infected peripheral venous catheters
  • Common in patients with prosthetic heart valves (most common cause < 60 daysfollowing surgery) or pacemakers/ICDs

• Staphylococcus aureus

  • especially acute presentation, more severe, large vegetation
  • prosthetic valves, intravascular catheters; implanted devices (pacemakers, defibrillators),
  • IVDUs
  • Usually fatal within 6 weeks (if left untreated)

• Coagulase-negative Staphylococcus -- indwelling intravenous catheters, prosthetic valves, pacemakers or defibrillators

• Enterococci -- Nosocomial urinary tract infections

• Pseudomonas aeruginosa and Serratia marcescens - IVDU

• Streptococcus bovis (Group D) /gallolyticus and Clostridium septicum - are associated with colorectal cancer or IBD

• Clostridium septicum is even more frequently associated with colonic pathology than Streptococcus bovis.

• Fungal -- after open heart surgery; immunocompromised host, chronic indwelling catheters, prolonged antibiotic therapy

• non-infective: systemic lupus erythematosus (Libman-Sacks) - at both sides of the heart valve, malignancy: marantic endocarditis

  particularly mucinous cystadenocarcinoma

  forms at the inferior side of heart valve

N.B.

Staphylococcal endocarditis is more common in those without underlying heart disease and is the most common cause of healthcare associated IE.

Strep. viridans is the most common cause of (community-acquired) subacute IE, especially in predamaged native valves (mainly the mitral valve) and in prosthetic valves (≥ 60 days after surgery)

• Common cause of IE following dental procedures

Culture negative causes

• prior antibiotic therapy
• Candida sp. - most common fungal cause