Leuconostoc species-associated endocarditis.

Leuconostoc species are gram-positive cocci belonging to the Streptococcaceae family. The species were generally regarded as nonpathogenic and of little importance in clinical microbiology until several occurrences of Leuconostoc infections were reported in the literature. Unlike many gram-positive bacteria, Leuconostoc species commonly demonstrate high-level resistance to vancomycin, with preserved sensitivity to most other antibacterial agents. We describe a 55-year-old man who developed endocarditis caused by Leuconostoc species sensitive to vancomycin. The patient received an aortic valve replacement and was treated with penicillin G and gentamicin; he experienced no further complications.