Case report: prosthetic valve endocarditis due to a nutritionally variant streptococcus.

The first report of prosthetic valve endocarditis due to a nutritionally variant streptococcus is presented. A 21-year-old woman developed persistent fever within one week of mitral valve replacement. Prosthetic valve dysfunction developed necessitating valve replacement. Cultures of blood and the excised prosthetic valve using routine media were negative; Streptococcus mitior grew as satellite colonies around Staphylococcus aureus and in beef heart infusion broth supplemented with 0.001% pyridoxine HCl. Treatment with penicillin G and streptomycin for six weeks was curative. Nutritionally variant streptococci should be considered in patients with prosthetic valve endocarditis and negative routine cultures.