2026 Southeastern Residency Conference

Background/Purpose: Antimicrobial-resistant organisms are a growing public health threat and contribute to increased morbidity and mortality, longer hospital stays, and higher healthcare costs. In particular, the utilization of anti-pseudomonal beta-lactam antibiotics significantly contributes to the development of resistance in addition to increasing the risk of complications such as Clostridioides difficile infections. The purpose of this study is to review and evaluate the effectiveness and safety of empiric cefepime and piperacillin/tazobactam de-escalation through an implemented Pseudomonas aeruginosa risk stratification tool utilized by the antimicrobial stewardship team.  

Methodology: This study is a single-center, retrospective cohort study including patients admitted to St. Francis Hospital Downtown from January 2025 to August 2025. Data for this study was obtained from the electronic medical record, which includes clinical, pharmaceutical, and laboratory information. Patients were identified via antimicrobial stewardship intervention notes for P. aeruginosa risk stratification. The primary outcome sought to elucidate effectiveness, defined as re-escalation of antibiotics due to infectious cause or clinical deterioration. Secondary outcomes were centered around safety, defined as total days of antimicrobial therapy, development of Clostridioides difficile infection, readmission rate within 90 days, and NHSN Standardized Antimicrobial Administration Ratio (SAAR) data pre and post intervention. Patients were included in this study if they had an active order for cefepime or piperacillin/tazobactam, are 18 years of age or older, and have documentation of completed screening by the antimicrobial stewardship team. Patients were excluded if they had positive microbiological results at the time of audit before de-escalation by the antimicrobial stewardship team, duplicate patients, or de-escalation not pursued. The impact of antimicrobial stewardship intervention on the utilization and de-escalation rates of antipseudomonal beta-lactam antibiotics were evaluated using descriptive statistics. 

Results: A total of 523 patients were screened for inclusion, of which 278 were included in the analysis for the primary and secondary outcomes. The most frequent indication prompting anti-pseudomonal beta-lactam de-escalation was intra-abdominal infection (104/278, 37.4%). The mean duration of broad-spectrum anti-pseudomonal beta-lactam therapy prior to intervention was 2 days (SD 1.95). The total number of days on de-escalated therapy was 751 versus the total days of anti-microbial therapy (de-escalated + initial + re-escalated) was 1513 days. For the primary endpoint, 15 patients (15/278, 5.4%) required re-escalation of anti-microbial therapy. The most common regimen used for de-escalation was ceftriaxone plus metronidazole (104/278, 37.4%). The most common reason for re-escalation was suspected worsening infection or clinical deterioration (13/15, 86.7%), and the most frequently used medication for re-escalation was piperacillin/tazobactam (8/15, 53.3%). Regarding the secondary endpoint of safety, 1 patient developed Clostridioides difficile infection after intervention. Additionally, 106 patients (106/278, 38%) were readmitted within 90 days from initial admission.  

Conclusion: Based on the primary outcome findings, empiric de-escalation of anti-pseudomonal beta-lactams using risk stratification appears to be effective, as only a small proportion of patients (5.4%) required re-escalation of antimicrobial therapy. These results are consistent with previous studies demonstrating that patients without risk factors for Pseudomonas aeruginosa are unlikely to have infection with this organism and therefore be appropriately managed with narrower spectrum antimicrobial therapy. Regarding secondary outcomes, only one patient developed Clostridioides difficile infection following de-escalation. However, a relatively high readmission rate (38%) within 90 days from initial admission was observed. This may be attributed to factors such as inadequate source control and re-escalation of antibiotics initiated in the emergency department and continued during subsequent admissions. Future investigations evaluating further de-escalation beyond ceftriaxone may be warranted, given its relatively broad spectrum of activity compared to other antimicrobial options.