Antimicrobial Resistance in Isolates from Inpatients and Outpatients in the United States: Increasing Importance of the Intensive Care Unit

To compare the occurrence of antimicrobial resistance in hospitals with that in the community, we analyzed data for isolates collected from inpatients and outpatients in eight U.S. hospitals. The percentage of resistant isolates from inpatients was higher than that from outpatients for the following combinations of antimicrobials and organisms: methicillin/coagulase-negative Staphylococcus (49.0% vs. 36.0%, respectively; P < .01); methicillin/Staphylococcus aureus (33.0% vs. 14.5%, respectively; P < .01); ceftazidime/Enterobacter cloacae (26.0% vs. 12.0%, respectively; P < .01); imipenem/Pseudomonas aeruginosa (12.0% vs. 6.5%, respectively; P < .01); ceftazidime/P. aeruginosa (7.8% vs. 4.0%, respectively; P < .01); and vancomycin/Enterococcus species (6.3% vs. 1.4%, respectively; P < .01). There was a significant stepwise decrease in the percentage of resistant organisms isolated from patients in the intensive care unit (ICU), non-ICU inpatients, and outpatients. These results suggest that resources allocated to control antimicrobial resistance should continue to be focused in the hospital, particularly in the ICU.