Subacute bacterial endocarditis

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Subacute bacterial endocarditis

Subacute bacterial endocarditis (SBE) is a slower, longer-lasting form of infective endocarditis that affects the heart valves, usually when there is pre-existing valve disease.

Causes
- Viridans group streptococci from the mouth (examples: Streptococcus mutans, S. mitis, S. sanguis, S. milleri)
- Other streptococci (e.g., Streptococcus intermedius)
- Enterococci from urinary tract infections
- Coagulase-negative staphylococci

How it happens
- Damaged heart valves provide a place for bacteria that enter the bloodstream to stick and grow, forming clumps called vegetations. The infection progresses slowly compared with acute endocarditis.

Signs and symptoms
- Malaise
- Weakness
- Night sweats
- Fever

Diagnosis
- Blood cultures: three samples taken over about a 24-hour period to identify the organism
- The presence of signs such as Osler’s nodes, Roth’s spots, or nail clubbing can support the diagnosis
- Imaging (like ultrasound) may show vegetation on a valve, but the diagnosis mainly relies on cultures and symptoms

Treatment
- Four weeks or more of high-dose intravenous penicillin
- Often combined with an aminoglycoside (such as gentamicin)

History note
- The first successful penicillin treatment for SBE was reported by Leo Loewe in 1944

See also
- Endocarditis