# P-1678. Gram-Negative Rod Bacteremia due to Organisms not Detected on the BioFire® Blood Culture Identification 2 (BCID2) Panel: Time to Effective Antimicrobial Therapy

## TL;DR

This study shows that nearly 25% of patients with certain bacteria not detected by a rapid diagnostic test still lacked effective treatment 12 hours later, with anaerobic bacteria causing longer hospital stays.

## Contribution

The study evaluates the clinical impact of undetected Gram-Negative Rod bacteremia by the BioFire® BCID2 panel on time to effective therapy.

## Key findings

- 24% of patients lacked effective therapy 12 hours after a negative BCID2 result.
- Anaerobic pathogens like Bacteroides thetaiotaomicron and Fusobacterium spp. were linked to longer hospital stays.
- Aerobic pathogens such as Pseudomonas putida and Achromobacter spp. had a 20-hour longer time to effective therapy compared to anaerobes.

## Abstract

The BioFire® BCID2 panel has revolutionized rapid diagnostics, reducing time to organism identification and targeted therapy. Despite detectability of 16 additional organisms and resistance genes compared to the original panel, limited data exists regarding the clinical impact of BCID-2 negative Gram-Negative Rod (GNR) bacteremia cases.

We evaluated the effect of BCID2-negative GNR bacteremia on time to effective therapy (TTET). Overall, 135 patients had BCID2-negative GNR bacteremia from July 2020 to August 2024. Further analysis examined the distribution of BCID-2 negative GNR pathogens and compared clinical outcomes between aerobic and anaerobic cases. Descriptive statistics were used to summarize patient characteristics. Chi-square and Wilcoxon Rank Sum tests were used to compare health outcomes. P-values were statistically significant if they were less than a pre-specified alpha level of 0.05.

At 12 hours post-BCID2 result, 24% (32/135) of patients lacked effective therapy. This group consisted of 15 aerobes and 17 anaerobes, with a median (interquartile range) TTET of 41 (20-51) hours. A 20-hour increase in median TTET was observed in the aerobic group vs. the anaerobic group: 47 (39-59) vs. 27 (18-42), p=0.02. Aerobes not on effective therapy were led by Pseudomonas putida (13%), Achromobacter spp. (13%), Brucella anthropi (13%), and Myroides spp. (13%). Despite these findings, a 7-day increase in median hospital length of stay (LOS) was observed among anaerobes: (17 (10-34) vs. 10 (7-19) days, p=0.01), with Bacteroides thetaiotaomicron (n=23) and Fusobacterium spp. (n=27) accounting for 60% (50/83) of the anaerobic pathogens.

These findings indicate that nearly 1 in 4 patients lacked effective therapy 12 hours after a negative BCID2 result. Over half of these cases involved anaerobic pathogens, particularly Bacteroides thetaiotaomicron and Fusobacterium spp., which were associated with a prolonged hospital LOS.

Christopher R. Frei, PharmD, FCCP, BCPS, Amgen: Grant/Research Support|AstraZeneca: Grant/Research Support