Review Question - QID 104935

The constellation of signs and symptoms is consistent with subacute infective endocarditis. In the setting of a recent periodontal procedure, the most likely causative organism is Streptococcus viridans.

Infective endocarditis refers to infection of the heart valves and is associated with a number of causative organisms. Risk factors for infective endocarditis include a history of rheumatic or structural/valvular heart disease, IV drug use, immunosuppression, or presence of a prosthetic heart valve. The causative organism underlying bacterial endocarditis can be suggested by the clinical context. Patients with poor dentition or a history of oral/perioral procedures are at increased risk of infective endocarditis caused by Streptococcus viridans, which colonize the oral cavity. The suggested approach to prophylaxis with amoxicillin during high-risk procedures (e.g. dental procedures with gingival involvement or GI/GU procedures in patients with active infection) has been hotly debated; current guidelines recommend antimicrobial prophylaxis for patients with the highest risk baseline conditions, such as having a prosthetic heart valve, prior history of endocarditis, or unrepaired cyanotic heart disease.

Pierce et al. review the diagnosis and treatment of endocarditis. They argue that antibiotic treatment of infective endocarditis depends on the valve (native vs. prosthetic), as well as the causative organism and its antibiotic susceptibilities. Commonly cultured organisms include Staphylococcus aureus, Streptococcus viridans, enterococci, and coagulase-negative staphylococci.

Chen et al. conducted a case-control study involving 736 patients with newly diagnosed infective endocarditis to investigate whether the improvement of oral hygiene through dental scaling, a periodontal procedure to remove plaque from the mouth, could reduce the risk of developing infective endocarditis. They found that the risk of infective endocarditis decreased significantly among patients who received dental scaling at least once per year, with an odds ratio of 0.696 (P = 0.005).

Figure A depicts a splinter hemorrhage, a non-blanching, linear, reddish-brown lesion found under the nail bed that is nonspecific for endocarditis. Figure B depicts Osler's nodes, which are painful, red, raised lesions found on the hands and feet; these are caused by immune complex deposition and are relatively specific to infective endocarditis. Illustration A depicts a transesophageal echocardiogram with a mitral vegetation; this can be a cause of mitral regurgitation and the onset of a pansystolic murmur. Illustration B depicts Roth spots, retinal hemorrhages with white or pale centers seen on fundoscopic exam in bacterial endocarditis.

Incorrect Answers:
Answer 1: Staphylococcus aureus is a common cause of acute bacterial endocarditis, particularly in IV drug users, but would not be as likely given the recent history of the periodontal procedure and the subacute presentation.
Answer 2: Staphylococcus epidermidis colonizes the skin and is a known cause of subacute infective endocarditis, but is less likely in this case given the history of the periodontal procedure.
Answer 4: Streptococcus pneumoniae is a potential cause of infective endocarditis (in addition to pneumonia and other infections), though it is less likely in this case given the history of the periodontal procedure.
Answer 5: Enterococcus faecalis would be more likely to cause infective endocarditis following cystoscopy in the setting of a UTI.