Results
ESBL-E, ESBL-E carriage, 19,122
Between January 2014 and August 2016, 19,122 patients were admitted to the participating wards during contact isolation periods and had a length of stay ≥2 days. At least 1 culture was collected for 16,091 patients (84.1%), yielding 32,253 samples. The median length of stay was 7 days (IQR, 4–11) among screened patients and 4 days (IQR, 3–7) among unscreened patients (Among all patients screened, 2,078 ESBL-E carriers were identified. The ESBL-E admission prevalence was 10.0% (95% confidence interval [CI], 9.6%–10.6%), with 1,572 (76%) of 2,078 ESBL-E carriers positive on admission. After day 3 and thus later than the interval predetermined for admission screening, 506 ESBL-E carriers (24%) were first detected with ESBL-E. Among the 8,613 patients screened twice, 472 (5.3%; 95% CI, 4.8%–5.8%) had new acquisition of ESBL-E; these 472 comprised 22.7% of ESBL-E cases. Data on previous admissions to the same ward were available for 2,058 ESBL-E carriers, of whom 523 ESBL-E carriers (25%) were readmitted.Figure 
Overview of ESBL-E carriers stratified into groups of patients with history of previous ESBL-E carriage, patients newly identified through active surveillance cultures, and patients discharged before healthcare workers could be notified.
Description of ESBL-E Carriers and the Isolation Compliance in Total and Stratified by Defined GroupsAmong the 2,078 ESBL-E carriers, 1,224 (59%) were placed in contact isolation at some time during their stay on the ward. The median lengths of stay were 12 days (IQR, 7–21) among isolated ESBL-E carriers and 5 days (IQR, 4–8) among nonisolated ESBL-E carriers.ESBL-E carriers identified through screening cultures in time for subsequent contact isolation [group 3, comprising 697 (34%) of all ESBL-E carriers] accounted for 9,607 (51%) of 18,698 ESBL-E days. Because of the delay between collecting the sample and initiation of contact isolation, 28% of those were nonisolated ESBL-E days [2,723 (15%) of 9,607 ESBL-E days] (Table 
Number of patient days before the first positive sample and identified ESBL-E days with and without contact isolation, stratified by ESBL-E carrier group.The median durations between collecting the positive sample and initiation of contact isolation were 4 days IQR, 2–5 days) among patients without a prior history of ESBL-E carriage, both among the 1,006 previously unknown ESBL-E carriers positive on admission and 4 days IQR, 3–6 days) among the 472 ESBL-E carriers who were first identified during their stay on the ward. Supplementary Table Figure 
Percentage and number of patient days identified ESBL-E days with and without contact isolation by ESBL-E carrier status.