LONG-TERM EFFECTS OF SELECTIVE DECONTAMINATION ON ANTIMICROBIAL RESISTANCE

Objective: To determine whether selective decontamination of the diges tive tract exerts any long-term effects on antimicrobial resistance pa tterns. Design: A surveillance and interventional study comparing the antimicrobial sensitivity patterns of clinically important bacterial i solates the year before a 2-yr, double-blind, randomized, controlled s tudy of selective decontamination of the digestive tract, and for the year thereafter when no use of the regimen was made. Setting: A ten-be d respiratory intensive care unit (ICU) in a 1,200-bed teaching hospit al. Patients: All 1,528 patients admitted to the ICU over the 4-yr stu dy period were included. There were 406 patients admitted in the year before the study of decontamination of the digestive tract (65% medica l, 23% surgical, and 12% trauma), of whom 76% required mechanical vent ilation. There were 719 patients admitted during the 2-yr study of sel ective decontamination (55% medical, 28% surgical, and 17% trauma), of whom 79.6% required mechanical ventilation. There were 403 patients a dmitted in the subsequent year (61% medical, 25% surgical, and 14% tra uma), of whom 76.9% required mechanical ventilation. Interventions: We performed daily clinical monitoring to detect nosocomial infection, w ith microbiological investigation when clinically indicated, as well a s twice-weekly routine microbiological surveillance sampling. Antimicr obial susceptibility testing using standard laboratory methods was als o performed. Selective decontamination of the digestive tract included parenteral cefotaxime and oral and enteral polymyxin E, amphotericin B, and tobramycin. Measurements and Main Results: The occurrence rate of nosocomial infection was 20.6%, 16.6%, and 25.3%, respectively, in the three study periods. In the year after selective decontamination, there was an increase in the occurrence rate of infection (p = .005), with an associated increase in infections caused by the Enterobacteria ceae, while a reduction in the level of resistance to the third-genera tion cephalosporins was found (p = .07). There was a progressive incre ase in the occurrence rate of infections caused by Acinetobacter speci es (p = .05). Only 11 infections over the 4 yrs were caused by Enteroc occus species. Staphylococcal infections were uncommon (5.7% of admiss ions), and the level of methicillin resistance did not change. No incr ease in aminoglycoside resistance occurred. Conclusion: No long-term e ffects on antimicrobial resistance or the spectrum of nosocomial patho gens could be attributed to the use of selective decontamination of th e digestive tract over a 2-yr period in a respiratory ICU admitting al l categories of patients.