Objective: To determine risk factors of infections with piperacillin/tazobactam-resistant Escherichia coli in critical care patients.
Design: Prospective, consecutive sample survey study.
Setting: Surgical intensive care unit (ICU) in a university hospital.
Patients: A consecutive series of 133 patients from whom culture results were positive for E. coli during their ICU stay.
Interventions: None.
Measurements and main results: Multivariate logistic regression analysis identified the following significant independent factors associated with the emergence of a piperacillin/tazobactam-resistant Escherichia coli: prior use of amoxicillin (odds ratio, 4.15) and amoxicillin/clavulanate (odds ratio, 3.25).
Conclusions: Treatment with amoxicillin or amoxicillin/clavulanate is a major risk factor for the detection of piperacillin/tazobactam-resistant E. coli in ICU patients.