1. Intensive Care Unit, Hospital General Universitario Gregorio Marañón, Madrid, Spain;
2. Intensive Care Unit, Hospital Universitario del Mar, Barcelona, Spain;
3. Surgical Intensive Care Unit, Hospital Universitario La Paz, Madrid, Spain;
4. Intensive Care Unit, Hospital Universitario de Galdákano- Usansolo, Galdakao, Spain;
5. Microbiology Department, Hospital Universitari i Politecnic La Fe, Valencia, Spain;
6. Intensive Care Unit, Hospital Universitario Ramón y Cajal, Madrid, Spain;
7. Intensive Care Unit, Hospital Universitario Dr. Peset, Valencia, Spain