Infection is a relatively common complication of trauma, particularly among patients with a greater severity of injury. Although exsanguinating hemorrhage and central nervous system injury are the most common causes of early mortality, patients who die more than 48 hours after injury often succumb to infectious complications or their consequences.

Trauma-related infection represents either infection at an original site of injury or infection that occurs as a direct result of the injury. Examples of the former are an infected soft-tissue laceration or osteomyelitis at the site of an open fracture. The latter include empyema after a penetrating wound to the chest and an intra-abdominal abscess that follows a gunshot wound to the colon. Infection also may occur at sites remote from the area of injury; however, these infections usually are related to the use of invasive monitoring devices or lifesaving treatments such as mechanical ventilation, and will not be discussed further.

Injury can lead to infection by (1) direct contamination of a sterile site with exogenous microorganisms; (2) disruption of the natural epithelial barrier of the gastrointestinal, respiratory, or gynecologic tract, with contamination from endogenous microorganisms; (3) impairment of local antimicrobial clearance mechanisms by direct damage to tissue and the introduction of substances such as foreign bodies or hematomas that act as adjuvants to promote infection; and (4) impairment of systemic antimicrobial defenses through secondary effects related to the consequences of injury.