Haemophilus paraphrophilus endocarditis in a prolapsed mitral valve

A case of Haemophilus paraphrophilus endocarditis successfully treated with ampicillin is described. The patient, a 24-year-old woman, had a prolapsed mitral valve. The organism was initally misidentified as H. parainfluenzae, which it closely resembles. H. paraphrophilus is distinguished by its requirement of 10% CO2 for growth on NaCl-free medium and its inability to ferment xylose.