Figure 1.

Study flow diagram. No cases of urosepsis due to Klebsiella pneumoniae were identified. Fifty-nine cases of urosepsis secondary to an extended-spectrum β-lactamase– producing strain of Escherichia coli were identified initially, which led to selection of 118 controls (based on a 1:2 ratio). One of the 59 cases was later found to be a duplicate and was therefore excluded from the analysis; all 118 controls were retained in the analysis.