Infective endocarditis due to anaerobic and microaerophilic bacteria.

Seven cases of infective endocarditis (IE) due to anaerobic or microaerophilic bacteria were seen in a period of 42 months at Rancho Los Amigos Hospital (Downey, California), representing 10.6 percent of the total number of 66 cases that carried the diagnosis of IE. Five of the 66 patients had polymicrobial endocarditis. Three of five patients with polymicrobial endocarditis had at least one anaerobic or microaerophilic microorganism isolated from the blood, and all five patients practiced intravenous drug abuse. Six of the seven patients with anaerobic or microaerophilic IE were women. The three patients who had anaerobic Gram-negative bacillary endocarditis were drug abusers. None of the isolated organisms were Bacteroides fragilis. The following heart valves were involved in the seven patients with anaerobic or microaerophilic IE: tricuspid (three), mitral (two), aortic (one) and tricuspid plus aortic (one). Three of the seven patients had preexistent valvular disease, and two required tricuspid valvulectomy. Only one patient had serious systemic embolism (cerebral), but all four drug abusers had septic pulmonary embolism. All seven patients recovered with appropriate antimicrobial therapy.