Gram-Negative anaerobic endocarditis: two case reports and review of the literature.

The rarity of anaerobic gram-negative endocarditis limits the ability of physicians to define its prognosis. Two cases of endocarditis due to Bacteroidesfragilis are described, and a review of the English literature for all cases of anaerobic gram-negative endocarditis reported since 1940 is presented. The disease predominantly affects males. Clinical features are similar to those of endocarditis due to nonanaerobic organisms, but underlying heart disease is less common and the rate of thromboembolic complications is high. All deaths reported were due to Bacteroides spp.; no deaths due to Fusobacterium spp. have been reported. Treatment with metronidazole has dramatically improved the prognosis of patients with endocarditis due to anaerobic gram-negative bacilli.