This study was designed to evaluate the effect of a targeted preoperative Methicillin-resistant Staphylococcus aureus (MRSA) detection by polymerase chain reaction (PCR) on either endogenous or exogenous postoperative MRSA infections in a high risk population undergoing gastroenterological surgery. The primary endpoint was to investigate whether the potentially high incidence of MRSA infections in patients with MRSA nasal colonization before surgery can be prevented with a PCR-based strategy. The second endpoint was to investigate the impact of acquisition of MRSA colonization after surgery on the occurrence of MRSA infections. Investigators hypothesize that postoperative MRSA infection is prevented by a targeted screening strategy in preoperative MRSA carrier, and there is limited effect in patients with postoperative MRSA acquisition.