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Infective endocarditis is an infection of the heart valves or the heart’s inner lining, known as the endocardium. Infective endocarditis is usually caused by a bacteria or a fungus. A Bacterial Endocarditis occurs when a bacterial infection from other parts of the body enter the bloodstream (usually resulting in bacteremia) and attack the lining of the heart or the heart valves.

What are the other Names for this Condition? (Also known as/Synonyms)

  • Bacterial Infection of the Endocardium
  • Heart Valve Bacterial Infection
  • Subacute Bacterial Endocarditis (SBE)

What is Bacterial Endocarditis? (Definition/Background Information)

  • Infective endocarditis is an infection of the heart valves or the heart’s inner lining, known as the endocardium. Infective endocarditis is usually caused by a bacteria or a fungus
  • A Bacterial Endocarditis occurs when a bacterial infection from other parts of the body enter the bloodstream (usually resulting in bacteremia) and attack the lining of the heart or the heart valves
  • Bacteremia occurs when bacteria that normally live on the skin, reside in the oral cavity, or in the lining of the intestinal tract, enters the bloodstream through small cuts or abrasions and cause a health condition. Bacteremia can also occur following certain medical procedures involving the mouth, throat, gastrointestinal and genitourinary tract
  • Bacterial Endocarditis can occur at any age, but it generally affects individuals older than 50 years of age. Common organisms associated with this infection include Staphylococcus aureus, Streptococcus viridians, and Enterococci species
  • The signs and symptoms of Bacterial Endocarditis are highly variable ranging from low-grade fever, fatigue, and joint pain, to severe features that include stroke (sudden weakness of limbs or face due to disruption of brain’s blood supply), cardiac arrhythmias, and damage to kidney and spleen
  • The treatment of Bacterial Endocarditis is based on the specific bacteria type causing the infection. The mainstay of treatment is through intravenous antibiotics; surgery may be required in some cases
  • Untreated Bacterial Endocarditis can lead to an extremely poor prognosis and can almost always be fatal. With appropriate early diagnosis and treatment, the outcomes are better. However, the prognosis also depends upon a set of factors including the type of organism causing infection, the health status of the individual, and the presence of any heart illness, among other factors

Who gets Bacterial Endocarditis? (Age & Sex Distribution)

  • Bacterial Endocarditis is mostly seen in middle-aged and elderly adults over 50 years old, though individuals of any age are at risk
  • Both males and females are affected
  • It may equally affect individuals of all racial and ethnic background and no preference is noted

Note: Individuals with normal immune function, normal heart condition, and a healthy lifestyle are not prone to Bacterial Endocarditis.

What are the Risk Factors for Bacterial Endocarditis? (Predisposing Factors)

Bacterial Endocarditis is uncommon in general population, but individuals with certain heart conditions have a greater risk of acquiring it. A normal heart is typically resistant to infections, but a damaged area in the heart provides a roughened surface for microorganisms to attach and multiply.

The risk factors for Bacterial Endocarditis may include the following factors:

  • Any cause of bacteremia that may include medical procedures such as:
    • Oral surgery, tooth extraction
    • Abdominal surgery
    • Genitourinary surgery; prostate resection
    • Diagnostic procedures such as upper GI endoscopy, colonoscopy, and barium enema
    • Transesophageal echocardiography
    • Placement of intravascular catheters
    • Poor oral hygiene and aggressive brushing of teeth can also result in bacteremia
  • Heart valve related:
    • Placement of an artificial (prosthetic) valve
    • Heart valve repaired with a prosthetic material
    • Age related degeneration of the heart valves
    • Valvulopathy, or heart valve disease, arising in a transplanted heart
  • Heart related:
    • Previous history of endocarditis
    • Certain congenital heart diseases
    • Rheumatic heart disease: An autoimmune response of the heart to a bacterial infection of the throat (caused by Streptococcus pyogenes)
  • Intravenous (IV) drug abuse: Needles that are used to inject illegal drugs are sometimes contaminated with bacteria, which can cause Bacterial Endocarditis
  • HIV and AIDS patients, because of suppressed immune system
  • Poorly-controlled diabetes
  • Longstanding corticosteroid therapy

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Bacterial Endocarditis? (Etiology)

Bacterial Endocarditis is caused by several kinds of bacteria that include:

  • Staphylococcus aureus: It is the most common cause of bacterial infection. It is usually found in healthcare settings and enters the bloodstream after procedures such as a surgery. It may also lead to infections secondary to intravenous injections of illicit drugs
  • Streptococcus viridans: These bacteria are normal residents of oral cavity and enter the bloodstream after dental procedures, such as cleaning and tooth extraction
  • Staphylococcus epidermidis, which usually attacks the prosthetic heart valves
  • Enterococci: It can cause endocarditis in those with gastrointestinal tract, genital and urinary tract abnormalities, or due to procedures such as colonoscopy or cystoscopy
  • Streptococcus bovis: It is usually associated with colonic cancers
  • Methicillin-resistant Staphylococcus aureus (MRSA)
  • HACEK group of organisms: A group of gram-negative bacteria that live in the gums and in individuals with poor dental hygiene. It is also seen in intravenous (IV) drug users who regularly contaminate their needles with saliva. HACEK organisms include the following bacteria:
    • Haemophilus species
    • Aggregatibacter species
    • Cardiobacterium species
    • Eikenella corrodens
    • Kingella species
  • Other gram-negative bacteria

Right-sided Bacterial Endocarditis usually occurs in IV drug abusers and in patients with intravenous catheter associated bacteremia (when bacteria enter the bloodstream through intravenous catheters).

What are the Signs and Symptoms of Bacterial Endocarditis?

The signs and symptoms of Bacterial Endocarditis may not always be severe; in many cases, it may be mild. In some, it may slowly develop over time, and hence, this may result in a delayed diagnosis. However, in some individuals, there may be a sudden onset of severe signs and symptoms.

Common signs and symptoms associated with Bacterial Endocarditis may include:

  • Low-grade fever, which comes and goes in a majority of individuals, and chills
  • Night sweats
  • Fatigue and malaise, which is a feeling of discomfort or uneasiness
  • Anorexia, or the lack of appetite; weight loss
  • Headache
  • Arthralgia or joint pain; stiff neck and backache
  • Chest pain (pleuritic pain), cough
  • Confusion
  • A new or changing heart murmur: It is an abnormal heart sound that can be listened with a stethoscope
  • Electrical abnormalities in the heart (cardiac arrhythmias)
  • Stroke: It is a condition in which blood supply to an area of the brain is disrupted that results in a weakness of certain part of the body such as an arm, leg, or face
  • Formation of septic emboli within the bloodstream (septic emboli are blood clots admixed with bacteria)
  • Abdominal signs and symptoms such as nausea/vomiting and abdominal pain
  • Janeway lesions, which are small, painless, red or hemorrhagic lesions on the palms and sloes
  • Osler’s nodes, which are painful, red, raised lesions mostly on distal fingers
  • Intracranial hemorrhage: Hemorrhage within the brain
  • Conjunctival hemorrhage: Conjunctiva is a membrane that lines the inside of the eyelid and the sclera (the white part of the eye)
  • Splinter hemorrhages: These are tiny blood clots under the finger nails
  • Kidney and spleen infarcts: Interruption of blood supply to the kidney and spleen resulting in permanent damage of some of their portions
  • Enlarged spleen
  • Glomerulonephritis: Damage to the kidneys resulting in the loss of blood and proteins in the urine
  • Roth’s spots: These are retinal hemorrhages and are seen with a fundoscope (an ophthalmoscope to view the inside of the eye)

How is Bacterial Endocarditis Diagnosed?

In order to diagnose Bacterial Endocarditis, the physician will initially perform a physical exam with evaluation of medical history. During a physical examination, the physician will look for the presence of the following:

  • Low-grade fever
  • A new or changing heart murmur
  • Janeway lesions
  • Osler’s nodes
  • Roth’s spots
  • Splinter hemorrhages
  • Conjunctival hemorrhages
  • Weakness/paralysis of a part of body (leg arm or face), which may be due to a brain stroke

Certain specific tests that may help in the diagnosis of Bacterial Endocarditis such as:

  • Blood cultures: Blood is drawn from a vein and sent to the laboratory, where it is placed on a special dish to see the growth of the bacteria responsible for causing endocarditis
  • Chest X-ray
  • Echocardiography: It is an ultrasound of the heart that is performed to assess cardiac function, size of the heart chambers, and the status of heart valves
  • Electrocardiogram or EKG for detecting conduction abnormalities of the heart

Bacterial Endocarditis is usually diagnosed using Duke’s diagnostic criteria for endocarditis, which consists of a combination of major criteria and minor criteria. A definitive diagnosis should satisfy any of the following conditions:

  • The presence of any 2 major criteria
  • The presence of 1 major criterion and 3 minor criteria
  • The presence of 5 minor criteria

Major criteria include the following:

  • 2 blood cultures positive for infectious organisms
  • Blood cultures that are positive for microorganisms, which are taken 12 hours apart
  • 3 blood cultures positive on separate occasions that are taken at least 1 hour apart
  • Abnormalities in echocardiogram showing either a mass or abnormal blood flow
  • Abscess of the heart
  • New abnormalities developing in a prosthetic valve (partial dehiscence of the valve)
  • Recent onset of regurgitation of the valve causing abnormal blood flow (valvular regurgitation)

Minor criteria include the following:

  • Previously diagnosed heart condition
  • A positive history of intravenous drug use
  • Fever above 38 deg. C
  • Presence of vascular infarcts, hemorrhage, aneurysm, and emboli occurring in any part of the body
  • Abnormal immune findings such as glomerulonephritis, positive rheumatoid factor, Osler nodes
  • Positive blood cultures that do not meet the criteria described in the ‘major criteria’
  • Abnormal echocardiogram findings not described in the ‘major criteria’

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Bacterial Endocarditis?

Bacterial Endocarditis, if not promptly treated can cause major complications. The complications may affect any part of the body and may include:

  • Mitral and aortic valve incompetence: The bacteria clump together with other cell fragments and form aggregates of bacterial growth (vegetations) on the heart valves. If not treated promptly, it might result in permanent damage to the valves
  • Congestive heart failure: Due to damaged heart valves, it is difficult for the heart to pump enough blood to meet the requirements of the body. This can eventually result in heart failure and death
  • Formation of myocardial abscesses: An abscess may develop within the heart muscle and cause abnormal heartbeat rhythms (electrical conduction defects)
  • Infections in other parts of the body (metastatic infections): Infected material and vegetations formed on the heart valves dislodge and travel through blood to infect other organs of the body resulting in lung, kidney, spleen, and brain abscesses
  • 40% of the individuals may have neurological complications, which usually results from bleeding in the brain (intracerebral hemorrhage), embolic stroke, multiple sites of brain infection caused by microabscesses
  • Heart failure; permanent heart damage

How is Bacterial Endocarditis Treated?

Bacterial Endocarditis is a serious infection and requires an early and effective treatment in a hospital setting. However, it can be completely cured if proper treatment is administered.

  • Treatment of bacterial infections:
    • Intravenous antibiotics, wherein antibiotics are given through the vein. Initially an empiric antibiotic is started usually vancomycin or ceftriaxone, which is then later modified depending upon the laboratory results
    • Sometimes surgery is needed to treat persistent infections not responding to antibiotic therapy
  • Surgery may be performed to remove the infected area in the heart, or to correct the heart valve abnormalities

How can Bacterial Endocarditis be Prevented?

Generally, individuals with normal immune function, normal heart condition, and a healthy lifestyle are not prone to Bacterial Endocarditis. Hence, the following precautionary measures can be adopted to reduce the risk of acquiring Bacterial Endocarditis:

  • Practice good oral hygiene every day, which may include:
    • Regular brushing and flossing of the teeth and gums; avoid aggressive brushing of teeth
    • Have regular dental checkups
    • Ensuring that dentures fit properly
  • Avoid any procedure that can potentially lead to skin infections including body piercings and tattoos
  • Ensuring that strict safety and standardized practices are observed during the performance of any diagnostic tests or surgical procedures within a hospital environment
  • Treat any heart-related illness or disease promptly
  • Avoiding the use of intravenous drugs
  • Controlling diabetes through suitable lifestyle changes
  • Immediately addressing any medical issues causing poor immune system, including appropriate treatment of HIV infection and AIDS
  • Frequent follow-up physician visits for individuals who have been diagnosed with endocarditis in the past

Previously, every individual who was considered at risk of developing endocarditis was advised to take antibiotics as a preventive measure before any dental, gastrointestinal and urinary tract procedure was undertaken.

However, the American Heart Association recommends antibiotic prophylaxis before certain dental procedures, only for individuals who are considered to have a high risk for endocarditis. Individuals who belong to such a high risk group include those with:

  • An artificial (prosthetic) heart valve
  • Unrepaired cyanotic congenital heart diseases (birth defects with oxygen levels lower than normal) such as Tetralogy of Fallot and transposition of great vessels
  • Incompletely treated congenital heart diseases
  • The first 6 months following the complete treatment of congenital heart disease
  • Heart valve disease that develops after a heart transplantation procedure

The American Heart Association, no longer recommends antibiotic prophylaxis prior to gastrointestinal and genitourinary procedures including gastroscopy, colonoscopy, and cystoscopy.

What is the Prognosis of Bacterial Endocarditis? (Outcomes/Resolutions)

Bacterial Endocarditis, if left untreated is almost always fatal. The prognosis depends on a set of factors that include:

  • The overall health condition of the individual
  • The type of bacteria causing the infection
  • The presence of any heart disease or heart abnormality
  • The presence of any prosthetic heart device
  • Surgical procedures involving the heart
  • The severity of the signs and symptoms and development of complications (if any)
  • History of IV drug abuse
  • Presence of other underlying conditions
  • Age of the individual

With early and effective treatment, individuals with Bacterial Endocarditis have a 70-90% survival rate.

The prognosis is known to be worse for the following group of individuals:

  • Older individuals
  • Infection with resistant organism
  • Long delay in treatment
  • Aortic and multiple valve involvement
  • Large vegetations or aggregates of bacterial growth
  • Prosthetic valve infection
  • Infection with Staphylococcus aureus
  • Major embolic event resulting in large damage to the kidney, spleen, or lungs
  • Left-sided endocarditis as compared to right-sided endocarditis

Additional and Relevant Useful Information for Bacterial Endocarditis:

Please visit our Heart & Vascular Health Center for more physician-approved health information:


What are some Useful Resources for Additional Information?

American Heart Association (AHA)
7272 Greenville Ave. Dallas, TX 75231
Phone: 1-800-AHA-USA-1, 1-800-242-8721, 1-888-474-VIVE
Email: Review.personal.info@heart.org
Website: http://www.heart.org

Centers for Disease Control and Prevention (CDC)
1600 Clifton Rd. Atlanta, GA 30333, USA
Phone: (404) 639-3534
Toll-Free: 800-CDC-INFO (800-232-4636)
TTY: (888) 232-6348
Email: cdcinfo@cdc.gov
Website: http://www.cdc.gov

References and Information Sources used for the Article:

http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/TheImpactofCongenitalHeartDefects/Infective-Endocarditis_UCM_307108_Article.jsp#.V443FPl96M8 (accessed on July 15, 2016)

http://circ.ahajournals.org/content/107/20/e185 (accessed on July 15, 2016)

http://www.mayoclinic.org/diseases-conditions/endocarditis/basics/definition/con-20022403 (accessed on July 15, 2016)

http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/infectious-disease/infective-endocarditis/ (accessed on July 15, 2016)

Helpful Peer-Reviewed Medical Articles:

Patanè, S. (2014). Is there a need for bacterial endocarditis prophylaxis in patients undergoing gastrointestinal endoscopy?. Journal of cardiovascular translational research, 7(3), 372-374.

Glenny, A. M., Oliver, R., Roberts, G. J., Hooper, L., & Worthington, H. V. (2013). Antibiotics for the prophylaxis of bacterial endocarditis in dentistry. The Cochrane Library.

Flaherty, M. L., Kleindorfer, D. O., Khoury, J. C., Alwell, K., Moomaw, C. J., Woo, D., ... & Martini, S. (2016). Abstract WP177: Bacterial Endocarditis and Acute Stroke: a Population-based Study. Stroke, 47(Suppl 1), AWP177-AWP177.

Loughrey, P. B., Armstrong, D., & Lockhart, C. J. (2015). Classical eye signs in bacterial endocarditis. QJM, hcv055.

Subesinghe, S., Dorr, A., & Ng, N. (2016). 008 An Unusual Presentation of Subacute Bacterial Endocarditis Manifesting as Infectious Forearm Pyomyositis. Rheumatology, 55(suppl 1), i65-i66.

Hung, T. H., Hsieh, Y. H., Tseng, K. C., Tsai, C. C., & Tsai, C. C. (2013). The risk for bacterial endocarditis in cirrhotic patients: a population-based 3-year follow-up study. International journal of infectious diseases, 17(6), e391-e393.

Cadranel, J. F., Ollivier-Hourmand, I., Bureau, C., Zerkly, S., Thévenot, T., Cacoub, P., ... & Lison, H. (2015). P0150: Liver cirrhosis is independently associated with mortality in patients with bacterial endocarditis: Results of a case control multicenter study of 202 cases. Journal of Hepatology, (62), S358.

Melgar, I. G., Guerra, L. O., & Mendizabal, H. (2016). PM243 Bacterial Endocarditis in Patients With Chronic Renal Failure Hemodialysis Catheter Users. Global Heart, 11(2), e111.