Antibiotic Therapy for Pyelonephritis in the Emergency Department

Acute pyelonephritis (APN) is a common diagnosis among patients presenting to the Emergency Department (ED). It is treated by empiric antibiotics within the ED. With a rise in antimicrobial resistance globally, it is unknown whether patients are being managed with empiric antibiotics that are appropriate for the causative organisms of APN. The aim of this study was to describe the pathogens causing APN and to assess whether the current choice of empirical antibiotics is appropriate.

A single-centre retrospective review of patients with a discharge diagnosis of APN at an adult tertiary referral hospital in metropolitan Melbourne over a 5-year period (2018-2022) was conducted. Eligible cases were identified from ICD-10 discharge diagnoses. Demographics, cultured organisms and antibiotic regimens were extracted using explicit chart review.

There were 557 patients included with APN with 569 urine samples cultured after initial assessment. The most common pathogen cultured was E. coli, identified in 232 (40.8%) culture results. There were 26 (4.7%; 95% CI: 3.1-6.6) patients managed in the ED with inappropriate antibiotics. This occurred most frequently when ampicillin or amoxicillin monotherapy was prescribed. Patients were discharged with inappropriate antibiotics in 76 (13.6%) cases. This occurred most commonly when no antibiotic was prescribed on discharge.

Most empiric antibiotic prescribing for APN was appropriate and sensitive against the cultured organism. E. Coli in urine samples was commonly resistant to amoxicillin, ampicillin or trimethoprim. Strict adherence to national clinical guidelines can further reduce the rates of inappropriate antibiotic prescriptions.