Comparison of an Emergency Department-Specific Antibiogram to Hospital Antibiogram: Influence of Patient Risk Factors on Susceptibility

BACKGROUND: Traditional antibiograms use local resistance patterns and susceptibility data to guide empiric antimicrobial therapy selection. However, antibiograms are rarely unit-specific and do not account for patient-specific risk factors. The objective was to develop an Emergency Department (ED)-specific antibiogram and evaluate the impact of risk factors on antimicrobial susceptibility. METHODS: This retrospective, single-center descriptive study used culture and susceptibility data from January 1 to December 31, 2016 to create an ED-specific antibiogram for the most commonly isolated organisms. Susceptibilities were then compared with the hospital antibiogram. All ED isolates were further stratified by the following risk factors: age, disposition from ED, previous antimicrobial use and/or hospitalization within 30 days, and presenting location. Descriptive statistics, Pearson Chi-Square/Fisher’s Exact Tests, and logistic regression were performed. A two-tailed p-value of <0.05 was considered statistically significant. RESULTS: A total of 2158 isolates from the ED were included: Escherichia coli (EC) (n = 1244), Klebsiella pneumoniae (KP) (n = 232), Proteus mirabilis (PM) (n = 131), Pseudomonas aeruginosa (PA) (n = 103), Staphylococcus aureus (SA) (n = 303), and Enterococcus faecalis (EF) (n = 145). The majority of patients were <65 years old (n = 1088) and presented from the community (n = 1800) with no antimicrobial exposure (n = 1628) nor hospitalization (n = 1895) within 30 days. There were no statistically significant differences between the ED and hospital antibiogram (n = 5739) for KP, PM, PA, SA, and EF. The hospital antibiogram overestimated EC resistance rates for cefazolin (20% vs. 15.6%, P = 0.049), ceftriaxone (9.6% vs. 6.4%, P < 0.033), and ciprofloxacin (23.7% vs. 15.4%, P < 0.006). There were significantly more risk factors present in patients discharged from the ED vs. those admitted (P < 0.0001). Healthcare facility residence had the greatest impact on susceptibility, especially EC (81.8% vs. 34.9%, P < 0.0001) and PM (75.3% vs. 33%, P < 0.0001) ciprofloxacin susceptibility. CONCLUSION: Development of an ED-specific antibiogram can aid physicians in prescribing appropriate empiric therapy when risk factors are included. DISCLOSURES: All authors: No reported disclosures.