Empirical antimicrobial therapy for bloodstream infections not compliant with guideline was associated with discordant therapy, which predicted poorer outcome even in a low resistance environment.

Objectives: To characterise all bloodstream infections (BSIs) in a low antimicrobial resistance (AMR) prevalence setting with regard to the appropriateness of empirical antimicrobial therapy, compliance with the national clinical practice guideline, de-escalation practice and outcome.

Methods: A retrospective observational study including patients aged 18 years admitted to a university hospital in central Norway with positive blood culture in 2019.

Results: We included 756 BSI episodes in our analysis. Empirical antimicrobial therapy was in accordance with the national guideline in 534 (70.6%), and not in accordance in 190 (25.1%) of the BSI episodes. There was a statistically significant association between compliance with the national guideline and concordant empirical antimicrobial therapy ( = .001). De-escalation of antimicrobial therapy was possible but not done in 217 (31.1%) of the BSI episodes. Variables identified as independent predictors of discordant empirical antimicrobial therapy included hospital department, type of empirical antimicrobial regimen, bacterial species, and AMR. Independent predictors of intra-hospital case fatality rate were coverage of empirical antimicrobial therapy, CCI-score, SAPS-II score, site of infection, and type of empirical antimicrobial regimen. Furthermore, the intra-hospital and long-term unadjusted all-cause case fatality rates were increased ( < .001, log-rank test for overall difference in survival) for the patients who received discordant empirical antimicrobial therapy.

Conclusion: Our study shows that empirical antimicrobial therapy initiated in accordance with national guideline recommendations increases the likelihood of receiving concordant therapy. Discordant empirical antimicrobial therapy was associated with poorer outcomes, even in a setting with low AMR prevalence.