Bacterial endocarditis is most commonly caused by

Ref Harrison 19 th ed pg 819 The causative microorganism is primar- ily responsible for the temporal course of endocarditis. b-Hemolytic streptococci, S. aureus, and pneumococci typically result in an acute course, although S. aureus occasionally causes subacute disease. Endocarditis caused by Staphylococcus lugdunensis (a coagulase- negative species) or by enterococci may present acutely. Subacute endocarditis is typically caused by viridans streptococci, enterococci, CoNS, and the HACEK group. Endocarditis caused by Baonella species, T. whipplei, or C. burnetii is exceptionally indolent.