From the Guidelines
The most common bacteria causing acute infective endocarditis are Staphylococcus aureus, Streptococcus species, and Enterococcus species, with Staphylococcus aureus being the predominant cause of acute presentations, especially in healthcare-associated infections, intravenous drug users, and patients with prosthetic valves. According to the most recent guidelines 1, for patients with acute clinical presentations of native valve infection, coverage for S aureus, β-hemolytic streptococci, and aerobic Gram-negative bacilli is reasonable. Some key points to consider in the management of infective endocarditis include:
- The bacteria typically enter the bloodstream through a portal of entry, adhere to damaged or abnormal heart valves, and form vegetations composed of platelets, fibrin, and microorganisms.
- Diagnosis requires blood cultures and echocardiography, while treatment involves prolonged intravenous antibiotics (typically 4-6 weeks) targeted at the specific organism, sometimes combined with surgical intervention for complications like heart failure, persistent infection, or large vegetations with embolic risk.
- Other less common but important pathogens include coagulase-negative staphylococci, HACEK organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella), and fungi like Candida species, as noted in earlier guidelines 1. The management of infective endocarditis should be guided by the identification of the causative organism and the clinical presentation of the patient, with consideration of factors such as the presence of prosthetic valves, intravenous drug use, and underlying medical conditions.
From the Research
Common Bacteria Causing Acute Infective Endocarditis
- Staphylococcus aureus is the most common microorganism causing infective endocarditis, accounting for 54.3% of cases 2
- Other common causes of infective endocarditis include:
- Viridans group streptococci (VGS)
- Coagulase-negative staphylococci (CoNS)
- Enterococcus spp
- Streptococcus bovis 2
Epidemiology and Pathogenesis
- The incidence of infective endocarditis is around 4/100,000 person years in the general population, and 15/100,000 over the age of 50 years 3
- Staphylococcus aureus is one of the most common infective agents of IE, and most commonly originates from nosocomial sources, e.g., intravenous and arterial catheters, pacemaker leads, and prosthetic valves 3
- Endocarditis caused by S aureus has a mortality rate of approximately 20% to 40% 3
Diagnosis and Management
- Rapid identification and susceptibility testing of the infecting organism are important in determining the choice of definitive antimicrobial therapy 4
- The optimal antimicrobial agent(s) and duration of treatment for SAIE are currently not known, but a minimum of 2 weeks of antimicrobial therapy is recommended for 'right-sided' SAIE, a minimum of 4 weeks for uncomplicated 'left-sided' SAIE, and a minimum of 6 weeks for complicated 'left-sided' or prosthetic valve SAIE 4