Bacterial and fungal infections cause infective endocarditis, or the inflammation of the innermost layer of the heart. Many bacteria and fungi can cause this heart disease, but just a small number of them cause the majority of the infections. Infective endocarditis can develop when people have a large amount of bacteria or fungi in their bloodstream and have heart abnormalities.
Infective Endocarditis
The endocardium is the innermost layer of the heart. Infective endocarditis is the infection and inflammation of the endocardium, and it is usually caused by bacterial and fungal infections. The infection not only affects the endocardium, but it affects the valves of the heart as well. In the developed countries of the world, there are 2.6 to seven cases of infective endocarditis each year for every 100,000 people, according to Dr. Adolf Karchmer, professor of medicine at Harvard Medical School, writing in "Harrison's Principles of Internal Medicine."
Bacteria and Fungi Involved
Many different bacteria and fungi can cause infective endocarditis, but just a few cause most of the infections. Streptococcus viridans can cause the disease if it reaches the heart after the bacteria enters the mouth. Staphylococcus aureus can cause infective endocarditis after it penetrates the skin. The HACEK bacteria include Haemophilus parainfluenzae, actinobacillus, cardiobacterium, eikenella and kingella. They can cause endocarditis after infecting the lungs. Streptococcus bovis can travel through the bloodstream and reach the heart from the intestines, while enterococcus originate in the urinary system. The main fungi that cause endocarditis are aspergillus and candida.
Risk Factors
The heart can usually resist infection because the constant flow of blood prevents bacteria and fungi from attaching to the endocardium. Thus, people usually develop endocarditis if they have abnormal heart valves or abnormalities in the endocardium, and have a large amount of bacteria or fungi in their bloodstream, explains Dr. Lawrence Pelletier Jr., professor of internal medicine at the University of Kansas School of Medicine, writing in The Merck Manual for Healthcare Professionals. Prosthetic, or artificial valves, are also a risk factor. Intravenous drug users develop endocarditis at a rate 40 times higher than the general population, according to Dr. Brigitte Baumann of the Cooper Health System, writing in "Tintinalli's Emergency Medicine."
Symptoms
People with infective endocarditis may have a low fever with chills, muscle aches, night sweats and weight loss. They may have Roth's spots, or blood clots in the retina of the eye which cause white spots surrounded by hemorrhaging. Some people have Janeway lesions, or red spots on their palms and soles. Others may develop Osler's nodes, or painful areas on their fingertips, or even small hemorrhages under their nails.
Outcome
Dr. Karchmer writes in "Harrison's Principles of Internal Medicine" that 55 to 70 percent of the people who develop infective endocarditis from an S. aureus infection survive this heart disease. Yet, 85 to 90 percent survive if the infection is caused by other bacteria. Those who develop the heart disease within two months of getting an artificial heart valve have a 50 to 60 percent survival rate. If they develop infective endocarditis later on, their survival rate increases to 80 to 90 percent. People do not die because the antibiotics failed, but do so because of other health problems along with heart complications.
References
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- The Merck Manual for Healthcare Professionals: Infective Endocarditis
- "Tintinalli's Emergency Medicine: A Comprehensive Study Guide"; Judith Tintinalli, M.D., Gabor Kelen, M.D. et al.; 2004
