Bacteraemia with Streptococcus agalactiae – an observational study on clinical aspects and time to blood culture positivity

Purpose
Streptococcus agalactiae causes severe infections. Time to blood culture positivity (TTP) has been suggested as a marker of disease severity. This study investigated the clinical characteristics of S. agalactiae bacteraemia and the association between TTP and outcomes.

Methods
This retrospective population-based study included adult episodes of S. agalactiae bacteraemia in southern Sweden, from 2016 to 2023. Medical records were reviewed. Information on TTP was obtained from the Department of Clinical Microbiology in Skåne. The primary outcome was 30-day mortality rate. Secondary outcomes were infective endocarditis (IE), development of sepsis and clinical deterioration within 48 h of blood culture collection.

Results
A total of 463 patients were included. Median age was 72 years (interquartile range (IQR 62–82). Skin and soft tissue were the most common focus of infection. IE occurred in 23 patients. 30-day mortality was 9% (n = 40). TTP analysis included 411 patients. There was no statistically significant difference in levels of TTP between patients with 30-day mortality and survivors, 8.6 h (IQR 7.6–10.1) vs. 9.1 h (IQR 7.8–10.4), p = 0.4. Patients with IE had statistically significantly lower levels of TTP compared to patients without IE, 7.5 h (IQR 5.9–8.8) vs. 9.1 h (IQR 7.9–10.5), p = 0.005.

Conclusion
S. agalactiae bacteraemia occurs in elderly patients, predominantly male, with a relatively high mortality. Shorter TTP was associated with the presence of IE, but not with mortality or sepsis, suggesting a potential role in identifying patients at risk for IE in S. agalactiae bacteraemia.