Antimicrobial r esistance in u rinary t ract i nfections at a l arge u rban e mergency d epartment: Factors c ontributing to e mpiric t reatment f ailure

Abstract Objective To calculate the emergency department (ED)-level Escherichia coli percentage of isolates susceptible to commonly used antibiotics and to determine the risk factors associated with inadequate empiric antibiotic therapy among patients treated for urinary tract infections (UTIs) in our ED. Methods Retrospective cohort study conducted at a large tertiary teaching hospital. Participants included patients older than 18 years of age who had a urine culture with growth of > 100,000 colonies of E. coli . Demographic and therapeutic choices associated with inadequate empiric antibiotic therapy were explored. Antimicrobial susceptibility pattern of E. coli isolates recovered from ED patients were calculated, and stratified by gender and age. Results A total of 300 unique patients had E. coli bacteriuria during the study period. Among patients who received at least one dose of antibiotic in the ED, variables independently associated with an increased risk of inadequate empiric therapy were age (relative risk [RR] 1.016; 95% confidence interval [CI] 1.001 – 1.031; P = 0 .032), male gender (RR 2.507; 95% CI 1.470 – 4.486; P = 0 .001), and use of fluoroquinolones (RR 2.128; 95% CI 1.249 – 3.624 P = 0 .005). Sub-group analysis of patients discharged from the ED showed that definitive therapy with nitrofurantoin decreased the risk of inadequate empiric antibiotic therapy by 80% (RR 0.202; CI 0.065 – 0.638; P = 0 .006). ED-level antibiograms showed differences in antimicrobial susceptibility of E. coli by age and gender. Conclusions Development of ED-level antimicrobial susceptibility data and consideration of patients ' clinical characteristics can help better guide selection of empiric antibiotic therapy for the treatment of UTIs.