Infective endocarditis caused by Streptococcus mutans. A complication of idiopathic hypertrophic subaortic stenosis.

Three patients with endocarditis caused by Streptococcus mutans were seen during a six-month period. All had clinical features of subacute bacterial endocarditis, including fever, heart murmurs, and positive blood cultures. One had underlying aortic insufficiency and two had idiopathic hypertrophic subaortic stenosis. All patients were treated with parenteral antibiotics and were cured. Streptococcus mutans is a pleomorphic, microaerophilic organism that is associated with dental caries and plaque. Differentiation of S mutans from enterococcal endocarditis is important because the former condition can be treated for a shorter period of time with penicillin alone, without the addition of aminoglycoside antibiotics.