Increases in community-acquired infections caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have important implications for hospital infection control and empirical antibiotic therapy protocols. We developed and validated a tool for identifying patients harboring these organisms at hospital admission.We retrospectively analyzed chart data for 849 adult inpatients. The derivation cohort included 339 patients admitted to a large Rome hospital during 2008, with (n=113) or without (n=226) culture positivity for ESBL-producing Escherichia coli, Klebsiella spp., or Proteus mirabilis within 48 h after admission. Logistic regression-based prediction scores were calculated based on variables independently associated with the outcome. The model was validated in a second cohort (n=510) selected with identical criteria in hospitals in Genoa and Turin during 2009.Prediction scores were based …