In our gastrointestinal surgical intensive care unit (SICU), the large number of patients with multiple enterostomies enhances the risk of nosocomial transmission of gut extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBLE) by health care workers. A control study performed in our SICU from June-August 1992 showed an ESBLE gut colonization rate of 70%. To reduce this rate, nursing procedures were intensified or modified, particularly handwashing, single-use equipment and waste control. To test the efficiency of these procedures, 64 patients hospitalized for more than two days from September 1992-March 1993 were screened for gut acquisition of ESBLE. Rectal samples were taken within 48 h after admission and then weekly. After nursing reorganization, the ESBLE colonization rate dropped significantly to 40% (P < 0.001). Twenty patients (31.7%) acquired a gut ESBLE, after a mean of 24.3 +/- 13.7 days. Each patient was colonized with one, two or three ESBLE (Klebsiella pneumoniae, Escherichia coli and Enterobacter aerogenes). Baseline characteristics of the 20 colonized and 39 non-colonized patients showed no significant difference (Student's t-test, P > 0.05). The nursing workload, estimated as a omega index, was greater in the colonized group (P < 0.001). These findings show that strict observance of nursing procedures can significantly reduce ESBLE acquisition in a high-risk surgical unit.