Infection control in critically ill patients: effects of selective decontamination of the digestive tract.

The use of selective decontamination of the digestive tract (SDD) to control infection in the intensive care unit (ICU) is reviewed. There are three basic patterns of infection in the ICU: primary endogenous, secondary endogenous, and exogenous. In exogenous infection, no microbial carriage precedes colonization and infection. In endogenous infection, infection is preceded by oropharyngeal or GI carriage. A primary endogenous infection is caused by an organism carried by the patient on admission to the ICU, whereas a secondary endogenous infection is caused by organisms acquired in the ICU. The traditional approach to infection control in the ICU has included frequent hand washing, limiting the use of agents for prophylaxis of stress-ulcer bleeding, and limiting the use of injectable antimicrobials to the treatment of infection in order to prevent resistance. The recognition that hand washing only partially reduces endogenous infection led to the use of nonabsorbable antimicrobials to abolish oropharyngeal and gastrointestinal carriage of potentially pathogenic microorganisms. In addition, the use of an injectable antimicrobial during the first four days in the ICU to control primary endogenous infection was considered not to lead to resistance as long as it was combined with nonabsorbable antimicrobials. Of 41 fully reported clinical trials of SDD, 33 showed a significant reduction of infectious morbidity among patients who received SDD. Of the 32 trials in which carriage of potential pathogens was a measured endpoint, 31 showed a reduction in carriage. Of the 24 studies in which resistance was an endpoint, 22 showed no increase in resistance associated with SDD. Only 10 of 35 trials that examined death showed a significant decrease in mortality. SDD, used in conjunction with traditional infection-control measures, diminishes microbial carriage and infectious morbidity in the ICU without increasing antimicrobial resistance.