subacute bacterial endocarditis

Subacute bacterial endocarditis (SBE) is a type of infectious endocarditis, which is an infection of the inner lining of the heart (endocardium) and heart valves. SBE is characterized by a slower, more insidious onset compared to acute bacterial endocarditis. It is typically caused by certain bacteria that are less virulent and more likely to be present in the bloodstream due to a low-grade infection elsewhere in the body. If left untreated, SBE can lead to severe complications and damage to the heart valves. Here are the key aspects of subacute bacterial endocarditis:

**1. Causative Organisms:**

   - SBE is primarily caused by bacteria from the viridans group, including Streptococcus viridans, as well as other less virulent bacteria such as Staphylococcus epidermidis.

   - These bacteria are part of the normal flora found in the mouth, throat, and gastrointestinal tract.

**2. Predisposing Factors:**

   - Certain conditions or medical procedures can increase the risk of developing SBE. These include:

      - Dental procedures that cause bacteremia (bacteria entering the bloodstream), such as dental cleanings or extractions.

      - Other invasive medical procedures that can cause bacteremia, such as gastrointestinal or genitourinary procedures.

      - Structural heart defects or abnormalities, including congenital heart defects and prosthetic heart valves.

      - Injecting drugs (e.g., intravenous drug use), which can introduce bacteria into the bloodstream.

**3. Pathogenesis:**

   - The pathogenesis of SBE involves the introduction of bacteria into the bloodstream (bacteremia) from an infection or medical procedure.

   - The bacteria can then adhere to the damaged areas of the heart valves or endocardium.

   - As the bacteria colonize and grow on the heart valves, they form vegetation - bulky masses composed of bacteria, fibrin, and inflammatory cells.

**4. Clinical Features:**

   - The symptoms of SBE can be nonspecific and may develop gradually over weeks to months.

   - Common symptoms include low-grade fever, fatigue, weight loss, night sweats, and mild joint pain.

   - There may also be signs of heart valve dysfunction, such as a new heart murmur or worsening of an existing murmur.

**5. Complications:**

   - SBE can lead to several serious complications, including:

      - Heart valve damage and dysfunction, which can cause heart failure or emboli (clumps of infected material that break off and travel to other parts of the body, leading to abscesses or organ damage).

      - Septicemia (bacterial infection in the blood), which can be life-threatening.

      - Glomerulonephritis (inflammation of the kidney's filtering units), leading to kidney damage.

**6. Diagnosis:**

   - The diagnosis of SBE is based on clinical features, blood cultures (to identify the causative bacteria), echocardiography (to detect heart valve abnormalities and vegetations), and other imaging studies.

**7. Treatment:**

   - Treatment of SBE involves prolonged courses of intravenous antibiotics, typically for 4 to 6 weeks.

   - The choice of antibiotics is based on the identified bacteria and their susceptibility to specific drugs.

   - In severe cases or when complications are present, surgical intervention to repair or replace damaged heart valves may be necessary.

Early diagnosis and prompt treatment are essential to improve outcomes and prevent complications in patients with subacute bacterial endocarditis. Prophylactic antibiotics may be recommended before certain medical or dental procedures in individuals with a high risk of developing SBE. Regular follow-up with healthcare providers is crucial for those at risk to monitor their heart health and manage potential risk factors.