Surveillance cultures from the original source of isolation (blood, bronchial aspirate, urines or drainage fluids) will be obtained on admission and repeated weekly, or whenever clinically needed, during and after treatment to monitor persistence versus eradication of A. baumannii at the infected site. In vitro activity of colistin and rifampicin will be checked against all A. baumannii repeat isolates to detect development of resistance. Identification and antibiotic susceptibility of A. baumannii isolates will be performed at each centre using an automated system. Species identification will be confirmed by molecular biology.