Etiology and Outcomes of Bloodstream Infections by Immunosuppression Type: A Population-Based Laboratory Surveillance Study.

BACKGROUND

An increasing proportion of the population receives immunosuppressive treatment. There is a lack of guidelines for bloodstream infections (BSIs) in this group. This study aims to provide a comprehensive analysis of the etiology and outcomes in BSI associated with underlying immunosuppression.

METHODS

This population-based laboratory surveillance study included all positive blood cultures in southern Sweden, from 2013 through 2023. Immunosuppression was defined using diagnostic codes, medications, and laboratory data. We defined 6 categories of immunosuppression: antineoplastic treatment, neutropenia, immunosuppressant medication, organ transplants, primary immunodeficiency, and human immunodeficiency virus infection.

RESULTS

In total, 8058 of 47 552 (16.9%) BSI episodes were associated with underlying immunosuppression. This proportion increased over time (rate ratio, 1.019 per year [95% confidence interval {CI}, 1.012-1.027], P < .001). Immunosuppression was associated with a higher degree of Enterococcus faecium (odds ratio [OR], 3.16 [95% CI, 2.63-3.78]) and Pseudomonas spp (OR, 2.51 [95% CI, 2.16-2.91]) etiology. Intrinsic cephalosporin resistance was more frequent in BSI episodes with underlying immunosuppression (OR, 1.45 [95% CI, 1.36-1.55]). The 30-day mortality rate was higher in BSI episodes with underlying immunosuppression, at 17.9% (1439/8044), compared to 12.5% (4880/39 089) in episodes without immunosuppression (OR, 1.54 [95% CI, 1.45-1.64]).

CONCLUSIONS

This study provides an updated summary of etiology and outcomes in BSI associated with immunosuppression. Underlying immunosuppression is increasingly prevalent among patients with BSI and is associated with resistance to cephalosporins and increased short-term mortality. Clinical guidelines for the management of BSI in immunosuppressed patients are warranted.