Infective endocarditis caused by Actinobacillus actinomycetemcomitans: report of four cases.

Four patients with infective endocarditis caused by Actinobacillus actinomycetemcomitans are reported. The clinical course was characterized by chronicity. Three of the four patients were treated with combined penicillin and aminoglycoside therapy on an empiric basis; the fourth patient was given ampicillin alone for 3 weeks. Cure was achieved in all four cases, with antibiotic therapy alone in the first three and ampicillin alone plus valve replacement surgery in the fourth patient. Further in vitro bactericidal data are needed, and actual therapy with ampicillin alone is desirable to see whether these patients with endocarditis of natural valves cannot be treated with ampicillin alone for a 3-week period.