ObjectiveTo define the epidemiology of broad-spectrum cephalosporin-resistant Gram-negative bacilli in intensive care units (ICUs) during a nonoutbreak period, including the prevalence, the risk factors for colonization, the frequency of acquisition, and the rate of infection.DesignProspective cohort study.SettingTertiary care hospital.PatientsConsecutive patients admitted to two surgical ICUs.Main Outcome MeasurementsSerial patient surveillance cultures screened for ceftazidime (CAZ) resistance, antibiotic and hospital exposure, and infections.Resultsor=to3 days, 26% acquired a CAZ-RGN. Of the 14 infections caused by CAZ-RGN, 11 (79%) were attributable to the same species present in surveillance cultures at admission to the surgical ICU.ConclusionsColonization with CAZ-RGN was common and was usually not recognized by clinical cultures. Most patients colonized or infected with CAZ-RGN had positive surveillance cultures at the time of admission to the surgical ICU, suggesting that acquisition frequently occurred in other wards and institutions. Patients exposed to first-generation cephalosporins, as well as broad-spectrum cephalosporins/penicillins, were at high risk of colonization with CAZ-RGN. Empirical treatment of nosocomial Gram-negative infections with broad-spectrum cephalosporins, especially in the critically ill patient, should be reconsidered. (Crit Care Med 1999; 27:1090-1095)