Species-level reporting of Coagulase-negative staphylococci with MALDI-TOF does not impact clinical outcomes

Diagn Microbiol Infect Dis.

2026 May 25;116(3):117479.

PMID: 42217282

DOI: 10.1016/j.diagmicrobio.2026.117479

Abstract

Background: Coagulase-negative Staphylococci (CoNS) are common blood culture contaminants, yet distinguishing true infection from contamination remains challenging. In January 2023, we implemented routine species-level CoNS reporting. This study aimed to evaluate the impact of this intervention on antibiotic utilization, accuracy of true bacteremia diagnosis and clinical outcomes.

Methods: We conducted a retrospective study of adult inpatients with CoNS-positive blood cultures from July 2022 to June 2023. Two randomly selected cohorts; pre and post-implementation were compared. The primary outcome was antistaphylococcal antibiotic days of therapy. Secondary outcomes included true bacteremia based on Souvenir's criteria and clinical outcomes. Categorical and continuous variables were compared using Chi-square and Mann-Whitney U tests.

Results: Baseline demographic and clinical characteristics were similar between groups. Implementation of species-level identification did not significantly reduce antistaphylococcal antibiotic use (median 4.5 vs. 3 days, p = 0.39), early antibiotic discontinuation, or ID consultation rates. Identification of true bacteremia was similar by clinical judgment (28% vs. 25%, p = 0.63). In cases deemed contaminants, antibiotic duration decreased slightly post-intervention but was not statistically significant. Souvenir's criteria demonstrated higher sensitivity (80.3%) but lower specificity (77.4%) compared with clinical judgment, with a high negative predictive value (91.9%). Length of stay and mortality did not differ between groups.

Conclusions: Routine species-level identification of CoNS did not significantly affect antibiotic utilization, diagnostic accuracy, or clinical outcomes in this single-center cohort. Larger, prospective studies are needed to determine whether integrating rapid species identification with targeted stewardship interventions can improve outcomes.

antimicrobial stewardship | Bacteremia | Blood cultures | Coagulase-negative staphylococci | Species-level identification