Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is faster than traditional screening methods for detecting anaerobic gram-negative bacteria bloodstream infections, Cleveland Clinic researchers reported at the 2026 Critical Care Congress, in Chicago.
“There was at least a 30-hour difference” between the two techniques when applied to infections involving a single microorganism (i.e., monomicrobial), reported Nour Khankan, PharmD, a PGY-2 critical care pharmacy resident at the Cleveland Clinic Main Campus, in Cleveland. The results, Dr. Khankan stressed, have important implications for teams tasked with improving the efficiency of their antibiotic stewardship efforts.
She added that the findings highlight a key difference between the two detection methods. Traditional assays for anaerobic gram-negative bacteria rely on specialized anaerobic cultures, while MALDI-TOF MS uses lasers to identify these bacteria directly from positive blood cultures. Because those anaerobes grow slowly, traditional methods can delay detection—potentially affecting patient care, Dr. Khankan explained.
The researchers retrospectively assessed whether MALDI-TOF MS accelerated detection of anaerobic gram-negative bacteria after the clinic changed detection methods. In the study, 197 samples were assessed using traditional assays, of which 148 were identified as monomicrobial. An additional 408 cases were analyzed using MALDI-TOF MS, with 254 classified as monomicrobial. The most common pathogen in both groups was a Bacteroides species from an intraabdominal source.
Participants in both groups had similar levels of comorbidities such as chronic kidney disease or diabetes mellitus, and were of similar ages (median, 67 years of age for the traditional analysis group, 72 in the MALDI-TOF MS cohort), Dr. Khankan reported.
The study’s primary outcome was the time from Gram stain detection to pathogen identification, with a secondary focus on the impact of more rapid detection on antibiotic de-escalation. The median time to detection using MALDI-TOF MS was 15 hours in monomicrobial samples (IQR, 7.8-47.8), compared with 45.3 hours for established methods that require anaerobic culture (IQR, 41.5-49.3) (P<0.001).
MALDI-TOF MS maintained its speed advantage across the entire sample, although it was not as pronounced as with monomicrobials and not statistically significant (45.8 hours for the 107 traditional samples vs. 36.7 hours for the 408 MALDI-TOF MS samples; P=0.15).
The investigators also documented a difference in antibiotic de-escalation between the two groups, specifically in relation to monomicrobial infections, Dr. Khankan noted. The average time to de-escalation in the traditional group was 52 hours (n=29; IQR, 24.0-64.5); in the MALDI-TOF MS group, de-escalation commenced at 21.1 hours (n=29; IQR, 7.9-51.6) (P=0.01). These analyses relied on an established antibiotic spectrum scoring tool (Infect Control Hosp Epidemiol 2014;35[9]:1103-1113).
“These results support the use of rapid pathogen identification methods for patients with anaerobic gram-negative bloodstream infections,” concluded Dr. Khankan, who published this work with Cleveland Clinic colleagues in October 2025 (Microbiol Spectr 2025;13[12]:e0238325).
The sources reported no relevant financial disclosures.