Subacute bacterial endocarditis, abbreviated SBE, is a type of endocarditis (more specifically, infective endocarditis). Subacute bacterial endocarditis can be considered a form of

type III hypersensitivity Type III hypersensitivity, in the Gell and Coombs classification of allergic reactions, occurs when there is accumulation of immune complexes ( antigen- antibody complexes) that have not been adequately cleared by innate immune cells, giving ri ...

Signs and symptoms

Among the signs of subacute bacterial endocarditis are: *

Malaise As a medical term, malaise is a feeling of general discomfort, uneasiness or lack of wellbeing and often the first sign of an infection or other disease. The word has existed in French since at least the 12th century. The term is often used ...

* Weakness * Excessive sweat * Fever

Causes

It is usually caused by a form of Viridans group streptococcus bacteria that normally live in the mouth (''

Streptococcus mutans ''Streptococcus mutans'' is a facultatively anaerobic, gram-positive coccus (round bacterium) commonly found in the human oral cavity and is a significant contributor to tooth decay. It is part of the " streptococci" (plural, non-italic lowercase ...

, mitis, sanguis ''or ''milleri''). Other strains of streptococci can cause

subacute In medicine, describing a disease as acute denotes that it is of short duration and, as a corollary of that, of recent onset. The quantification of how much time constitutes "short" and "recent" varies by disease and by context, but the core deno ...

endocarditis as well. These include

streptococcus intermedius ''Streptococcus intermedius'' is an aerotolerant anaerobic commensal bacterium and a member of the ''Streptococcus anginosus'' group. The ''S. anginosus'' group, occasionally termed “''Streptococcus milleri'' group” (SMG) display hemolytic a ...

, which can cause acute or subacute infection (about 15% of cases pertaining to infective endocarditis).

Enterococci ''Enterococcus'' is a large genus of lactic acid bacteria of the phylum Bacillota. Enterococci are gram-positive cocci that often occur in pairs (diplococci) or short chains, and are difficult to distinguish from streptococci on physical charact ...

from urinary tract infections and coagulase negative staphylococci can also be causative agents.

Mechanism

The mechanism of subacute bacterial endocarditis could be due to malformed stenotic valves which in the company of bacteremia, become infected, via adhesion and subsequent colonization of the surface area. This causes an inflammatory response, with recruitment of matrix metalloproteinases, and destruction of collagen. Underlying structural valve disease is usually present in patients before developing subacute endocarditis, and is less likely to lead to septic emboli than is acute endocarditis, but subacute endocarditis has a relatively slow process of infection and, if left untreated, can worsen for up to one year before it is fatal. In cases of subacute bacterial endocarditis, the causative organism (streptococcus viridans) needs a previous heart valve disease to colonize. On the other hand, in cases of acute bacterial endocarditis, the organism can colonize on the healthy heart valve, causing the disease.

Diagnosis

Diagnosis of subacute bacterial endocarditis can be done by collecting three blood culture specimens over a 24-hour period for analysis, also it can usually be indicated by the existence of: *

Osler's node Osler's nodes are painful, red, raised lesions found on the hands and feet. They are associated with a number of conditions, including infective endocarditis, and are caused by immune complex deposition. Their presence is one definition of Osler' ...

s * Roth's spots * Nail clubbing

Treatment

The standard treatment is with a minimum of four weeks of high-dose intravenous

penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...

with an aminoglycoside such as

gentamicin Gentamicin is an antibiotic used to treat several types of bacterial infections. This may include bone infections, endocarditis, pelvic inflammatory disease, meningitis, pneumonia, urinary tract infections, and sepsis among others. It is not e ...

. The use of high-dose antibiotics is largely based upon animal models. Leo Loewe of Brooklyn Jewish Hospital was the first to successfully treat subacute bacterial endocarditis with penicillin. Loewe reported at the time seven cases of subacute bacterial endocarditis in 1944.

Signs and symptoms

Causes

Mechanism

Diagnosis

Treatment

See also

References

Further references

External links