Impact of Rapid Pathogen Identification of Gram-Negative Anaerobes on Antimicrobial Stewardship

Sunday, March 22, 2026

9:45 AM - 10:45 AM Central Time

Location: Connections Central - RST 05

Nour Khankan, PharmD (she/her/hers)

Ohio

Disclosure(s): No relevant financial relationship(s) to disclose.
TR

Thomas Rust, PharmD

Infectious Disease Pharmacy Specialist
Cleveland Clinic Main Campus

Disclosure information not submitted.
AP

Andrea Pallotta, PharmD, BCPS, BCIDP, AAHIVP

Infectious Disease Pharmacy Specialist
Cleveland Clinic Main Campus

Disclosure information not submitted.
SB

Stephanie Bass, BCCCP, BCPS, PharmD

Medical ICU Clinical Specialist
Cleveland Clinic Foundation

Disclosure information not submitted.
CR

Christine Ramsey, MPH, MLS(ASCP)

Microbiology Laboratory Manager
Cleveland Clinic Main Campus

Disclosure information not submitted.
BB

Bethany Burns, DO

Medical Microbiology
Cleveland Clinic Foundation

Disclosure information not submitted.
DR

Daniel Rhoads, MD

Section Head of Microbiology
Cleveland Clinic Main Campus

Disclosure information not submitted.
CK

ChungYun Kim, PharmD, BCIDP

Infectious Disease Pharmacy Specialist
Cleveland Clinic Main Campus

Disclosure information not submitted.

Introduction: Anaerobic gram-negative bacteria are an important but understudied cause of bloodstream infections (BSIs). Traditional pathogen identification methods for anaerobes may take several days largely due to the slow growing nature of anaerobes. The objective of this study was to evaluate the impact of using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS ) to rapidly identify anaerobic gram-negative bacteria directly from positive blood culture broth (PBCB) samples.

Methods: A retrospective, pre-/post-intervention study was conducted at the Cleveland Clinic Health System across 14 hospitals. Patients with blood cultures positive for anaerobic gram-negative bacteria from January 1, 2019, to August 1, 2024, were included. The pre-intervention group used conventional identification methods requiring subculture, while the post-intervention group used direct-from-PBCB MALDI-TOF MS testing. The primary outcome was time from Gram stain to pathogen identification. The secondary outcome was time to first antibiotic modification, including escalation or de-escalation, as measured by a standardized antibiotic spectrum scoring tool.

Results: A total of 605 patients were included in the primary analysis (197 pre-intervention, 408 post-intervention). In monomicrobial BSI, the median time from Gram stain to organism identification was significantly reduced in the post-intervention group [15.0 hours (IQR: 7.8–47.8) vs. 45.3 hours (IQR: 41.5–49.3); p< 0.001]. In the secondary outcome cohort (n=200), time to first antibiotic de-escalation was significantly shorter in the post-intervention group for monomicrobial BSI [21.1 hours (IQR: 7.9–51.6) vs. 52.0 hours (IQR: 24.0–64.5); p=0.014]. No significant differences were observed in time to antibiotic escalation or in the overall cohort.

Conclusions: Rapid anaerobic gram-negative pathogen identification using MALDI-TOF MS directly from PBCB significantly reduced time to pathogen identification, being more pronounced in the monomicrobial subgroup, as well as time to antibiotic therapy de-escalation. These results support the use of rapid pathogen identification methods for patients with anaerobic gram-negative bloodstream infections.