1450. Risk Factors for Antibiotic Resistance of Escherichia coli Urinary Isolates in Outpatients

BACKGROUND: Antibiotic-resistant E. coli infections represent a major cause of morbidity and mortality, and pose a challenge to antibiotic stewardship. Patient age has been suggested as a key determinant of resistance patterns in studies based in the United States and Europe, although local antibiotic use patterns may affect this relationship. We analyzed results from clinical antibiotic susceptibility tests performed at a large reference laboratory to further examine the association of age with E. coli urinary tract resistance patterns in WA State. METHODS: We analyzed 5 years of E. coli antibiotic susceptibility data for outpatient urinary tract infections in WA State from a national clinical reference laboratory. We included only the first isolate recorded for each patient and calculated crude rates of resistance to antibiotics for the age groups of 50 years. In a multivariate logistic model, we tested the effect of patient age, year of antimicrobial susceptibility test submission, and sex on antibiotic resistance. RESULTS: Univariate analyses indicated that resistance rates differed significantly across patient age groups for ciprofloxacin and nitrofurantoin. Among females, resistance rates also differed significantly across patients age groups for amoxicillin-clavulanate and gentamicin. Logistic regression using data from male patients found the odds of resistance to be significantly greater in older individuals for ciprofloxacin (OR 2.59) and lower in older individuals for amoxicillin-clavulanate (OR 0.56). For females, logistic regression found the odds of resistance to be significantly greater for older individuals for amoxicillin-clavulanate (OR 1.43), ciprofloxacin (OR 3.04), ceftriaxone (OR 2.58), nitrofurantoin (OR 2.20), and gentamicin (OR 1.62). CONCLUSION: In WA State, the distribution of antibiotic resistance in E. coli urinary isolates varies with age, sex and the antibiotic of interest. Greater and more timely use of databases of susceptibility testing of clinical isolates from outpatient settings can allow for the creation of age-specific antibiograms to guide and improve stewardship. [Image: see text] DISCLOSURES: All authors: No reported disclosures.