Device-Related Infections in the Intensive Care Unit An

Abstract

Between 5% - 15% of all hospitalized patients around the world will develop an Hospital Acquired Infection during their hospital stay. An estimated 60% of these infections are thought to be related to the use of invasive devices. The paradox here is uncanny: these devices are both life-saving and life- threatening. The most commonly occurring device-related infections are ventilator-associated pneumonias (VAP), catheter related bloodstream infection (CRBSI) and catheter-associated urinary tract infections (CAUTI). A device related infection is defined as a host immune response to one or more microbial pathogens on an indwelling implant. An understanding of the pathogenesis of these infections provides a rationale for management. Development of device-related infections begins with colonization of the foreign material, followed by a complex metamorphosis by the microorganisms with resultant biofilm formation. In this surface-associated form, bacteria have altered phenotypic properties. This change, in conjunction with the physical protective layer provided by the biofilm, renders antimicrobial therapy ineffective when used alone. Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in the intensive care unit and is associated with major morbidity and attributable mortality. The major route for acquiring VAP is oropharyngeal colonization by the endogenous flora or by pathogens acquired exogenously from the intensive care unit environment. The stomach represents a potential site of secondary colonization and reservoir of nosocomial Gram-negative bacilli. Endotracheal-tube biofilm formation may play a contributory role in sustaining tracheal colonization and also have an important role in late-onset VAP caused by resistant organisms. Aspiration of microbe-laden oropharyngeal, gastric, or tracheal secretions around the cuffed endotracheal tube into the normally sterile lower respiratory tract results in most cases of VAP. Clinical criteria, used in combination, may be helpful in diagnosing VAP; however, the considerable inter-observer variability and the moderate performance should be taken into account. Bacteriologic data do not increase the accuracy of diagnosis as compared to clinical diagnosis. Quantitative cultures obtained by different methods, including BAL, mini-BAL or PSB seem to be rather equivalent in diagnosing VAP. Catheter-related bloodstream infection is defined as the presence of bacteraemia originating from an i.v. catheter. It is one of the most frequent, lethal and costly complications of central venous catheterization. It is also the most common cause of nosocomial bacteraemia.