Patient's Origin and Lifestyle Associated with CTX-M-Producing Escherichia coli: A Case-Control-Control Study

BACKGROUND: Global dissemination of Escherichia coli producing CTX-M extended-spectrum β-lactamases (ESBL) is a public health concern. The aim of the study was to determine factors associated with CTX-M- producing E. coli infections among patients hospitalised in the Assistance Publique-Hôpitaux de Paris, the largest hospital system in France (23 000 beds), through a prospective case-control-control study. METHODS/PRINCIPAL FINDINGS: From November 2008 to June 2009, 152 inpatients with a clinical sample positive for CTX-M-producing E. coli (cases), 152 inpatients with a clinical sample positive for non ESBL-producing E. coli on the day or within the three days following case detection (controls C1), and 152 inpatients with culture-negative clinical samples since the beginning of hospitalisation and until three days after case detection (controls C2) were included in ten hospitals of the Paris area. Factors studied were related to patient's origin, lifestyle and medical history as well as care during hospitalisation. Those independently associated with CTX-M-producing E. coli were determined. Three independent factors were common to the two case-control comparisons: birth outside of Europe (cases vs C1: OR(1) = 2.4; 95%CI = [1.3–4.5] and cases vs C2: OR(2) = 3.1; 95%CI = [1.4–7.0]), chronic infections (OR(1) = 2.9; 95%CI = [1.3–6.9] and OR(2) = 8.7; 95%CI = [2.0–39.7]), and antibiotic treatment between hospital admission and inclusion (OR(1) = 2.0; 95%CI = [1.0–3.8] and OR(2) = 3.3; 95%CI = [1.5–7.2]). Cases were also more likely to be (i) functionally dependent before hospitalisation than C2 (OR(2) = 7.0; 95%CI = [2.1–23.5]) and (ii) living in collective housing before hospitalisation than C2 (OR(2) = 15.2; 95%CI = [1.8–130.7]) when CTX-M-producing E. coli was present at admission. CONCLUSION: For the first time, patient's origin and lifestyle were demonstrated to be independently associated with isolation of CTX-M-producing E. coli, in addition to health care-related factors.