Streptococcal species as a prognostic factor for mortality in patients with streptococcal bloodstream infections

Streptococcal bloodstream infections (BSIs) are common, yet prognostic factors are poorly investigated. We aimed to investigate the mortality according to streptococcal species and seasonal variation.

Patients with streptococcal BSIs from 2008 to 2017 in the Capital Region of Denmark were investigated, and data were crosslinked with nationwide registers for the identification of comorbidities. A multivariable logistic regression analysis was performed to assess mortality according to streptococcal species and season of infection.

Among 6095 patients with a streptococcal BSI (mean age 68.1 years), the 30-day mortality was 16.1% and the one-year mortality was 31.5%. With S. pneumoniae as a reference, S. vestibularis was associated with a higher adjusted mortality both within 30 days (odds ratio (OR) 2.89 [95% confidence interval (CI) 1.20-6.95]) and one year (OR 4.09 [95% CI 1.70-9.48]). One-year mortality was also higher in S. thermophilus, S. constellatus, S. parasanguinis, S. salivarius, S. anginosus, and S. mitis/oralis. However, S. mutans was associated with a lower one-year mortality OR 0.44 [95% CI 0.20-0.97], while S. gallolyticus was associated with both a lower 30-day (OR 0.42 [95% CI 0.26-0.67]) and one-year mortality (OR 0.66 [95% CI 0.48-0.93]). Furthermore, with infection in the summer as a reference, patients infected in the winter and autumn had a higher association with 30-day mortality.

The mortality in patients with streptococcal BSI was associated with streptococcal species. Further, patients with streptococcal BSIs infected in the autumn and winter had a higher risk of death within 30 days, compared with patients infected in the summer.