Adults discharged from emergency departments for acute pyelonephritis face similar 14-day treatment failure rates regardless of whether they receive first-, second-, or third-generation oral cephalosporins, according to a multicenter study published October 6, 2026, in the Annals of Emergency Medicine. Led by Alicia E. Mattson, PharmD, of the Mayo Clinic in Rochester, Minnesota, the research evaluated 1,147 adult patients across 11 academic emergency departments in the United States between 2023 and 2025.

Treatment Failure Rates Across Cephalosporin Generations

The retrospective analysis revealed no statistically significant differences in 14-day treatment failure rates among the different cephalosporin-generation cohorts. Treatment failure occurred in 19.6% of patients receiving first-generation cephalosporins, compared with 17.6% in the second-generation group and 18.0% in the third-generation group. Investigators defined treatment failure as urinary symptom recurrence, a repeat emergency department or urgent care visit for a urinary tract infection, a new antibiotic prescription for urinary symptoms, or subsequent hospitalization.

Impact of Antimicrobial Resistance and Cefazolin Susceptibility

While broad-generation choice showed little overall difference in outcomes, baseline resistance patterns heavily influenced patient recovery. Empirical treatment demonstrated greater initial activity against cefazolin-susceptible isolates in the second-generation cohort at 91.5%, compared with 76.5% for first-generation and 80.6% for third-generation cohorts. Treatment failure struck 71.1% of patients with cefazolin-resistant isolates, contrasted with just 17.5% of those with susceptible isolates. Among the resistant group, 86% of failures stemmed directly from culture-reported resistance, whereas in the susceptible group, 28% of failures involved clinical worsening.

Risk Factors Linked to Treatment Failure

Researchers identified specific patient characteristics that increased the likelihood of adverse outcomes following discharge. Having at least one antimicrobial resistance risk factor raised the odds of treatment failure, yielding an adjusted odds ratio of 1.91 with a 95% confidence interval ranging from 1.37 to 2.64. Older age also carried an increased risk, with an adjusted odds ratio of 1.01 and a 95% confidence interval from 1.01 to 1.02. Study authors noted that these findings support an individualized approach to antimicrobial treatment selection that incorporates resistance patterns, patient-specific factors, and adverse event profiles.

Common Questions About Acute Pyelonephritis Oral Cephalosporin Study

Why was this study conducted across emergency departments?

Researchers sought to determine whether later-generation oral cephalosporins provided a clinical advantage over first-generation agents for patients with acute pyelonephritis discharged directly from emergency departments.

What limitations did the study authors identify?

The retrospective design limited verification of medication adherence and follow-up outside the participating health systems, while reliance on diagnosis codes and clinical criteria created potential for misclassification. The smaller sample size of the second-generation cephalosporin cohort reduced statistical power.

How was the patient database supported?

The REDCap database utilized for the study was funded by the National Center for Advancing Translational Sciences of the National Institutes of Health, and the authors reported having no conflicts of interest.