In addition, S. epidermidis poses a major diagnostic problem because it is also the first source of contamination of blood culture sample and intraoperative samples (in case of suspected infection of orthopedic material in particular). Thus, when a sample is positive for S. epidermidis, there is less than a 25% chance that it reflects true bacteremia in the patient and 30% of patients would inappropriately receive vancomycin following contaminated blood cultures. Differentiating a contamination of a blood or intraoperative sample from true S. epidermidis infection is therefore crucial for patient management because unnecessary antibiotic therapy is potentially responsible for the emergence of resistant strains, toxicity and additional costs.