Staphylococcus lugdunensis endocarditis--the hidden peril of coagulase-negative staphylococcus in blood cultures.

Reported here is a successfully treated case of native mitral valve endocarditis caused by Staphylococcus lugdunensis and a review of 47 similar cases reported in the English literature. In the literature review, perineal skin flora appeared to be the source of the organism in patients with endocarditis. Staphylococcus lugdunensis is generally susceptible in vitro to beta-lactam agents. If speciation is not performed, these bacteria might be mistaken for Staphylococcus epidermidis, a relatively avirulent bacterium that is a common contaminant of cultures. Prompt speciation can lead to earlier recognition of endocarditis and possibly enable earlier surgical intervention with improved outcome for this high-mortality infection. Multiple positive blood cultures yielding coagulase-negative staphylococci should be identified to the species level; endocarditis or another intravascular source of infection should be sought.