A diagnosis of infective endocarditis is definite if either the following pathological or clinical criteria are met:
One of these pathological criteria:

Histology or culture of cardiac vegetation, embolized vegetation, or intracardiac abscess from the heart finds microorganisms
Active endocarditisOne of these combinations of clinical criteria

Two major clinical criteria
One major and three minor criteria
Five minor criteriaDiagnosis of infective endocarditis is possible if one of the following combinations of clinical criteria is met:

One major and one minor criteria
Three minor criteria are fulfilled

Major criteria
Positive blood culture with typical IE microorganism, defined as one of the following:
Typical microorganism consistent with IE from two separate blood cultures, as noted below:
Viridans-group streptococci, or
Streptococcus bovis including nutritional variant strains, or
HACEK group, or
Staphylococcus aureus, or
Community-acquired enterococci, in the absence of a primary focus
Microorganisms consistent with IE from persistently positive blood cultures defined as:
Two positive cultures of blood samples drawn >12 hours apart, or
Three or a majority of ≥four separate blood cultures (with first and last sample drawn at least one hour apart)
Coxiella burnetii detected by at least one positive blood culture or IgG antibody titer for Q fever phase 1 antigen >1:800.
Highly penicillin-resistant strains of viridans group streptococci, nutritionally variant streptococci like Granulicatella sp., Gemella sp., Abiotrophia defectiva, and Enterococci are usually treated with a combination therapy consisting of penicillin and an aminoglycoside for the entire duration of 4–6 weeks.Some people may be treated with a relatively shorter course of treatment (two weeks) with benzyl penicillin IV if infection is caused by viridans group streptococci or Streptococcus bovis as long as the following conditions are met:

Endocarditis of a native valve, not of a prosthetic valve
A MIC ≤ 0.12 mg/l
A complication such as heart failure, arrhythmia, or pulmonary embolism occurs
No evidence of extracardiac complication like septic thromboembolism
No vegetations > 5 mm in diameter conduction defects
Rapid clinical response and clearance of bloodstream infectionAdditionally, oxacillin-susceptible Staphylococcus aureus native valve endocarditis of the right side can also be treated with a short 2-week course of a beta-lactam antibiotic such as nafcillin with or without aminoglycosides. The main indication for surgical treatment is regurgitation or stenosis. In active infective endocarditis, the surgery should remove enough leaflet tissue to ensure eradication of the infectious process. Subsequent valve repair can be performed in limited disease.