# Non-beta-lactam agents for definitive treatment of ampicillin-susceptible Enterococcus bacteremia: a single-center experience

## TL;DR

This study shows that non-beta-lactam antibiotics can effectively treat certain cases of ampicillin-susceptible Enterococcus bacteremia, especially in patients with specific risk factors.

## Contribution

The study provides real-world evidence supporting the use of non-beta-lactam agents for treating ampicillin-susceptible Enterococcus bacteremia.

## Key findings

- 27% of ASEB cases were treated with non-beta-lactam agents with no significant difference in mortality or relapse rates.
- Factors like penicillin allergy, cancer history, and ESRD were strongly associated with non-beta-lactam use.
- Combination therapy was only used in beta-lactam-treated patients, not in those receiving non-beta-lactam therapy.

## Abstract

To describe the use of non-beta-lactam agents (NBL) to treat ampicillin-susceptible Enterococcus bacteremia (ASEB), and to identify factors associated with their use.

A single-center retrospective study at a rural tertiary referral center was conducted to identify ASEB episodes between January 1, 2016, and 31 December, 2021. Patient, microbiological, infection, clinical management characteristics, and outcomes were compared between those who received NBL versus BL agents for definitive therapy. Multivariable logistic regression analysis was used to determine factors associated with NBL use.

158 episodes of ASEB in 153 patients were included. 43 episodes (27%) were treated with NBL for definitive therapy. Factors associated with NBL therapy were younger age, history of penicillin allergy, history of cancer, end-stage renal disease (ESRD), polymicrobial bacteremia, lack of metastatic foci, and lack of endocarditis. Combination therapy was used in 23% of those treated with BL therapy versus zero patients receiving NBL therapy. All-cause 30-day and 90-day mortality and 30-day relapse rate were not statistically different. In the regression model, NBL therapy was more likely in those with: younger age (AOR 0.95, p < .01), any penicillin allergy (AOR 5.87, p < .01), history of cancer (AOR 5.25, p < .01), ESRD (AOR 12.48, p < .001), and polymicrobial bacteremia (AOR 4.20, p < .01).

NBL was used as definitive treatment in 27% of ASEB with good clinical outcomes. This real-life experience suggests NBL can be successfully used to treat ASEB based on clinical discretion.