Clinical Characteristics and Mortality Predictors of Group B Streptococcus Bacteremia in Adults: A Multicenter Retrospective Cohort Study in Japan, 2015–2024

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Abstract
Background: Invasive group B Streptococcus (GBS) infection in nonpregnant adults is increasing, particularly among older adults and those with underlying comorbidities. However, multicenter data on prognostic factors for adult GBS bacteremia in Japan remain limited. Methods: We conducted a multicenter retrospective observational cohort study of adults with GBS bacteremia at 7 hospitals in western Japan between 2015 and 2024. Variables analyzed included clinical characteristics, infection sites, microbiological characteristics, and antimicrobial susceptibility profiles. Univariable and multivariable logistic regression analyses were performed to identify factors associated with 30-day mortality. Results: A total of 442 patients were included. Median age [interquartile range] was 75 [64–84] years, and 83.0% had at least 1 comorbidity. The overall 30-day all-cause mortality for GBS bacteremia was 9.3% (41/442), which rose to 39.3% (11/28) among patients with streptococcal toxic shock syndrome (STSS). In multivariable analysis, STSS was the strongest predictor of death (adjusted odds ratio [aOR], 9.16; 95% confidence interval [CI], 3.28–25.58), followed by immunosuppressive therapy (aOR, 4.62; 95% CI, 1.66–12.86), cirrhosis (aOR, 3.40; 95% CI, 1.23–9.40), respiratory infection (aOR, 3.30; 95% CI, 1.08–10.06), advanced renal dysfunction (aOR, 2.66; 95% CI, 1.09–6.52), and polymicrobial bacteremia (aOR, 2.40; 95% CI, 1.03–5.57), whereas skin and soft tissue infection was associated with lower mortality (aOR, 0.07; 95% CI, 0.01–0.53). Conclusions: Adult GBS bacteremia carries a high burden of short-term mortality, with a wide variety of clinical presentations, necessitating prompt diagnostic and therapeutic intervention.

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