[A blood culture containing coagulase-negative staphylococci: not always due to contamination].

: Staphylococcus lugdunensis (SL) is a species belonging to the group of coagulase-negative staphylococci (CNS). It can cause severe infections such as endocarditis. Three cases of endocarditis caused by SL are presented. The first case describes a 71-year-old man with a fever and endogenous endophthalmitis. The second case describes delirium in an 87-year-old woman, thought to be due to pneumonia. The third case describes a 76-year-old man with an infection of unknown origin. In all cases, the first blood cultures drawn were positive for CNS and considered to be contaminated. However, all three patients were finally diagnosed as having severe endocarditis caused by SL. Two patients underwent valve replacement, one patient died due to ongoing sepsis. The first CNS-positive blood cultures drawn were wrongly denoted as being contaminated. Physicians should be aware of the pathogenic potential of SL and rule out contamination.