The relationship between minimum inhibitory concentration and 28 day mortality in patients with a Gram-negative bloodstream infection: an analysis of data from a cohort study (BSI-FOO)

Rebecca N Evans; Jessica Harris; Chris A Rogers; Alasdair P MacGowan

doi:10.1093/jacamr/dlad009

The relationship between minimum inhibitory concentration and 28 day mortality in patients with a Gram-negative bloodstream infection: an analysis of data from a cohort study (BSI-FOO)

JAC Antimicrob Resist. 2023 Feb 1;5(1):dlad009. doi: 10.1093/jacamr/dlad009. eCollection 2023 Feb.

Authors

Rebecca N Evans¹, Jessica Harris¹, Chris A Rogers¹, Alasdair P MacGowan²

Affiliations

¹ Bristol Trials Centre, Bristol Medical School, University of Bristol, 1-5 Whiteladies Road, Clifton, BS8 1NU Bristol, UK.
² Bristol Centre for Antimicrobial Research & Evaluation (BCARE), Infection Sciences, Pathology, North Bristol NHS Trust, Bristol, UK.

Abstract

Objectives: To explore the association between MIC/EUCAST breakpoint ratio and 28 day mortality in patients with a Gram-negative bloodstream infection (BSI).

Methods: Using data from the Bloodstream Infection-Focus on Outcomes (BSI-FOO) observational study, we defined an average MIC/EUCAST breakpoint ratio that was updated daily to reflect changes in treatment in the first 7 days after blood culture. Cox regression analysis was performed to estimate the association between MIC/EUCAST breakpoint ratio and mortality, adjusting for organism and a risk score calculated using potential confounding variables. The primary outcome was 28 day all-cause mortality from the date of blood culture.

Results: Of the 1903 study participants, 514 met the eligibility criteria and were included in the analysis (n = 357 Escherichia coli, n = 6 Klebsiella and n = 151 Pseudomonas aeruginosa). The average age was 74.0 years (IQR 60.0-82.0). The mortality rate varied from 11.1% (in patients treated with an average MIC/EUCAST breakpoint ratio of 1) to 27.6% (in patients treated with antibiotics with an average MIC/EUCAST breakpoint ratio >1). After adjusting for risk score and organism, MIC/EUCAST breakpoint ratio was not associated with 28 day mortality (P = 0.148).

Conclusions: In an adjusted model controlling for potential confounding variables, there was no evidence to suggest a relationship between MIC/EUCAST breakpoint ratio and 28 day mortality in patients with a Gram-negative BSI.