From the Guidelines
Endocarditis is most commonly caused by bacterial infections, with Staphylococcus aureus and Streptococcus species being the predominant pathogens, as supported by the guidelines from the American College of Cardiology/American Heart Association task force on practice guidelines 1.
Common Causes of Endocarditis
The majority of cases (80%) are due to streptococcal and staphylococcal organisms, with Staphylococcus aureus being the most frequent organism in endocarditis resulting from intravenous drug abuse and accounting for 80% of tricuspid valve infections 1.
- Other common bacterial causes include:
- Enterococci, particularly Enterococcus faecalis and E. faecium, which account for 90% of enterococcal endocarditis and are often associated with malignancy or manipulation of the genitourinary or gastrointestinal tract 1.
- Coagulase-negative staphylococci, such as Staphylococcus epidermidis, which is the predominant offending organism in early prosthetic valve endocarditis 1.
- HACEK organisms (Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella), which have become an important cause of endocarditis and are known to cause large vegetations 1.
Risk Factors and Pathogenesis
Risk factors that predispose individuals to endocarditis include pre-existing heart valve abnormalities, prosthetic heart valves, intravenous drug use, indwelling catheters, recent dental or surgical procedures, and immunocompromised states.
- The pathogenesis typically involves damage to the endocardial surface, followed by platelet and fibrin deposition, creating a nidus for microbial attachment and colonization, as described in the guidelines 1.
- Once bacteria adhere to this site, they multiply and form vegetations composed of microorganisms, platelets, and fibrin, which can lead to valve destruction, heart failure, and embolic complications if not treated promptly with appropriate antibiotics.
From the Research
Common Causes of Endocarditis
The common causes of endocarditis can be identified through various studies, including:
- Staphylococcus aureus, which is the leading cause of infectious endocarditis 2
- Viridans group streptococci (VGS), coagulase-negative staphylococci (CoNS), Enterococcus spp, and Streptococcus bovis, which are also common causes of endocarditis 2
- Gram-negative bacilli, including HACEK, which can also cause endocarditis 3
Risk Factors for Endocarditis
Certain risk factors can increase the likelihood of developing endocarditis, including:
- Intravenous drug abuse, which can lead to right-sided endocarditis 4
- Presence of a prosthetic valve, which can increase the risk of endocarditis 4
- Underlying medical conditions, such as human immunodeficiency virus (HIV) infection 4
Microorganisms Involved in Endocarditis
The microorganisms involved in endocarditis can vary depending on the population and other factors, including:
- Staphylococcus aureus, which is the most common microorganism in many population subgroups 2
- Coagulase-negative staphylococci, which can be more common in certain subgroups, such as patients with implantable devices or prosthetic valves 2
- Enterococcus spp, which can also be a common cause of endocarditis in certain populations 2