Comparison of emergency department to hospital antibiograms: Influence of patient risk factors on susceptibility

Abstract

Objectives: 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.

Methods: This retrospective, single-center descriptive study used culture and susceptibility data from January 1 to December 31, 2016 to develop an Emergency Department (ED)-specific antibiogram and compare the antimicrobial susceptibilities of the most commonly identified organisms to the hospital antibiogram. All ED isolates were further stratified by the following risk factors that may influence antimicrobial susceptibility: age, disposition from ED, previous antimicrobial use and/or hospitalization within 30 days, and presenting location (i.e. healthcare facility residence versus community).

Results: A total of 2158 isolates from the ED were included: Escherichia coli (n = 1244), Klebsiella pneumoniae (n = 232), Proteus mirabilis (n = 131), Pseudomonas aeruginosa (n = 103), Staphylococcus aureus (n = 303), and Enterococcus faecalis (n = 145). There were no statistically significant differences between the ED and hospital antibiogram (n = 5739) with the exception of Escherichia coli. The hospital antibiogram overestimated Escherichia coli 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 admitted versus discharged from the ED (p < 0.001). Healthcare facility residence had the greatest influence on susceptibility, especially Escherichia coli (81.8% vs 34.9%, p < 0.001) and Proteus mirabilis (75.3% vs 33%, p < 0.001) ciprofloxacin susceptibility.

Conclusions: There were no statistically significant differences between the ED and hospital antibiogram with the exception of Escherichia coli. However, development of an ED-specific antibiogram can aid physicians in prescribing appropriate empiric therapy when risk factors are included.

Keywords: Antibiogram; Antimicrobial resistance; Antimicrobial stewardship; Antimicrobial susceptibility; Emergency department; Logistic regression.