The main objective is to identify new virulence factors produced by Staphylococcus lugdunensis that can be associated with clinical sign of severe infections and identified symptoms. The methodological approach is based on the comparison between the production of toxins by a given S. lugdunensis isolate classified in patients groups according to the infection clinically defined. Each group will be compared to the presence or not of studied virulence factors. Clinical features associated with toxin activity are not known for S. lugdunensis. This comparative approach is based on the hypotheses that drove to the definition of patient groups and their clinical criteria. However, in the absence of the evident correlation between production of toxins and kind of infection, the statistical evaluation will be completed by a multi-varied analysis. This approach has not been choosen first because of the multiple parameters that undergo during infection that may reveal relationships without true correlation. About the number of included patients in each defined group, if one of them does not reach the expected count, we still might extend inclusions to 3-6 months more. The presence of severe infections without usually defined risk is intriguing. For these last patients, we have planned, after their individual consent to achieve an exome sequencing. The obtained data will be compared to available resources for the human genome. By filtering data through usual protocols, we hope to able to focus onto few genes that evoke specific sensitivity to infections, e.g. severe endocarditis due to S. lugdunensis without defined risk.