# 291. Duration of Antibiotic Therapy for Uncomplicated Gram-Negative Bacteremia in Solid Organ Transplantation

## TL;DR

This study compares short and long antibiotic treatments for uncomplicated gram-negative bacteremia in transplant patients and finds no significant difference in outcomes.

## Contribution

The study introduces a novel use of the DOOR ranking system to evaluate outcomes of short versus long antibiotic durations in solid organ transplant patients.

## Key findings

- Shorter antibiotic durations (≤10 days) did not result in significantly worse outcomes compared to longer durations (>10 days).
- The source of infection and treatment strategies differed between the two groups, but overall outcomes were similar.
- Larger studies are needed to confirm the safety and efficacy of shorter antibiotic regimens in this patient population.

## Abstract

We hypothesize that short durations (≤10 days) of antibiotics for uncomplicated gram-negative bacteremia (GNB) would have similar clinical outcomes compared to long durations ( >10 days) in solid organ transplant (SOT) patients.

DOOR Probability Forest PlotFigure 1.Forest plot demonstrating the desirability of outcome ranking (DOOR) probabilities for each individual DOOR component (survival without adverse events, microbiologic failure, isolation of an MDR gram-negative in the blood, C. difficile infection or death) as well as the overall DOOR probability of having a more desirable outcome with < 10 days versus ≥10 days of antimicrobial treatment.

Forest plot demonstrating the desirability of outcome ranking (DOOR) probabilities for each individual DOOR component (survival without adverse events, microbiologic failure, isolation of an MDR gram-negative in the blood, C. difficile infection or death) as well as the overall DOOR probability of having a more desirable outcome with < 10 days versus ≥10 days of antimicrobial treatment.

A retrospective cohort review was conducted on patients admitted to University of Maryland Medical System hospitals from 1/1/2019 to 6/30/2024. Included patients were ≥18 years old with an uncomplicated GNB defined as a confirmed Enterobacterales bacteremia, source control, and clinical stability at 72 hours. The primary outcome was a Desirability of Outcome Ranking (DOOR) comparison between < 10 days versus ≥10 days of treatment. Each patient was assigned a DOOR rank from 1 (survival without adverse events) to 5 (death). Ranks 2-4 included patients who survived but had 1, 2, or 3 undesirable events occur during the 30-day follow-up period, respectively. Undesirable events included microbiologic failure, isolation of an MDR gram-negative in the blood, or C. difficile infection. Confidence intervals for the DOOR probability were calculated using the Halperin et al. (1989) method with a 95% confidence level, with a statistically significant two-sided p-value of < 0.05.

A total of 105 patients were included in this study, with 27 patients in < 10 day cohort and 78 patients in the ≥10 day cohort. The source of GNB was significantly different between groups (p=0.007), with the < 10 day cohort having more intrabdominal infections (48.2% vs 19.2%) and the ≥ 10 cohort having more urinary sources of infection (67.9% vs 37.0%). There were more patients with an oral switch in the ≥10 day treatment cohort (66.7% vs 33.3%, p=0.003). The overall DOOR probability of having a more favorable outcome with a treatment duration of < 10 days compared to ≥10 day treatment was not statistically different (44.7%, 95% CI: 36.8%, 52.9%; p = 0.1235), highlighting that longer durations of therapy were not associated with improved outcomes.

In patients with a solid organ transplant and uncomplicated GNB, there was no significant difference in outcomes when treated for < 10 days or ≥ 10 days. Further studies with larger sample sizes are needed to highlight the efficacy and safety of shorter antibiotic durations for uncomplicated GNB in solid organ transplantation.

Emily L. Heil, PharmD, MS, Wolters-Kluwer: Advisor/Consultant