Subacute Bacterial Endocarditis


Subacute Bacterial Endocarditis (SBE) is a bacterial infection that produces growths on the endocardium (the cells lining the inside of the heart). Subacute bacterial endocarditis usually (but not always) is caused by a viridans streptococci (a type of bacteria); it occurs on damaged valves, and, if untreated, can become fatal within six weeks to a year.


Endocarditis has traditionally been classified as acute or subacute based upon the pathogenic organism and the clinical presentation. This distinction has become less clear, however, and the less specific term "infective endocarditis" is now more commonly used.

Most patients who develop infective endocarditis have underlying cardiac disease, although this is frequently not the case with intravenous drug abusers and hospital-acquired infections.

Important factors that determine the clinical presentation are:

  • the nature of the infecting organism

  • whether the infection is superimposed upon preexisting abnormal cardiac structures

  • the source of infection, since endocarditis in intravenous drug abusers and infections acquired during open heart surgery have special features

More virulent organisms, Staphyloccus aureus in particular, tend to produce a more rapidly progressive and destructive infection. Patients are more likely to present with:

  • fever

  • early embolization (vegetation dislodging from the heart valve and traveling through the blood stream)

  • acute valvular regurgitation (back flow of blood in the heart)

  • abscess formation (pocket of infection)

Streptococcus viridans, enterococci, and a variety of other bacteria and fungi tend to cause a more subacute form of endocarditis. Streptococcal infection tends to be more chronic, though the average incubation period is 1 to 2 weeks.


Subacute bacterial endocarditis (SBE) is usually caused by streptococcal species (especially viridans streptococci), and less often by staphylococci.

SBE often develops on abnormal valves after asymptomatic bacteremias (bacteria traveling through the bloodstream) from infected gums, or from gastrointestinal, urinary, or pelvic procedures.


Most patients present with a fever that lasts several days to 2 weeks. Nonspecific symptoms are common. Cough, shortness of breath, joint pain, diarrhea, and abdominal or flank pain may be present.

About 90 percent of patients will have heart murmurs, but murmurs may be absent in patients with right-sided heart infections. A changing murmur is common only in acute endocarditis.


Endocarditis is suspected in a patient with a heart murmur and unexplained fever for at least one week, and in an intravenous drug abuser with a fever, even in the absence of hearing a murmur.

A definitive clinical diagnosis requires blood cultures that grow bacteria.

Echocardiography (ultrasound study of the heart) may visualize vegetations (growths) on heart valves.


Cure of endocarditis requires eradication of all microorganisms from the vegetation(s), usually on the heart valve.

Bacterial endocarditis almost always requires hospitalization for antibiotic therapy, generally given intravenously, at least at the outset. Most patients respond rapidly to appropriate antibiotic therapy, with over 70 percent of patients becoming afebrile (without a fever) within one week. Occasionally, therapy with oral antibiotics at home will be successful.

Antibiotic therapy must usually continue for at least a month.

In unusual cases, surgery may be necessary to repair or replace a damaged heart valve.


If bacterial endocarditis is not adequately treated, it can be fatal. This is dependent on the infecting organism. Even when treated, further damage to a heart valve may can to heart failure. In addition, blood clots can form and travel throughout the bloodstream to the brain or lungs.

It is important that you tell your dentist or physician about any risk factors you may have for endocarditis.

People with predisposing factors for bacterial endocarditis are those with:

  • prosthetic heart valves

  • previous bacterial endocarditis

  • congenital heart disease

  • rheumatic valve dysfunction

  • hypertrophic cardiomyopathy

  • mitral valve prolapse with valvular regurgitation

If these predispositions are present, the patient should be given antibiotics before most medical or dental surgeries and whenever any significant skin infection occurs. Your physician will recommend which antibiotic(s) to take before, and in some cases, after your procedure.