Patients with multiple trauma and head injuries are high-risk populations for developing nosocomial infections, which are the first cause of death after 3 weeks of admission. Pneumonia caused by methicillin-sensitive Staphylococcus aureus is the most frequent infection in patients with a decreased level of consciousness. Nevertheless, after 7 days of ventilation, Pseudomonas aeruginosa is the most frequently isolated microorganism in ventilator-associated pneumonia. Central nervous system infections represent only 4% of those experienced by trauma patients; however, if cerebrospinal fluid (CSF) leakage exists, the incidence increases to 50%. The diagnosis of meningitis is difficult because CSF biochemical data are not specific. Patients with spinal cord injuries are at greater risk for developing infections caused by multiresistant microorganisms because of their prolonged hospital stay.