Serotype distribution and clinical characteristics of Group B Streptococcus Bacteremia in nonpregnant adults: a 15-Year Multicenter Study in Korea.

Background: Group B Streptococcus (GBS) bacteremia in nonpregnant adults is of increasing concern, particularly among the elderly in underlying conditions. This study analyzed the serotype distribution, antimicrobial resistance patterns, and clinical characteristics of GBS bacteremia in nonpregnant adults over a 15-year period in two tertiary hospitals in Korea.

Methods: From 2007 to 2021, patients aged ≥ 19 years with GBS bacteremia were identified via retrospective electronic medical record review. GBS isolates were collected through a hospital-wide surveillance system and confirmed via MALDI-TOF-MS. Multilocus sequence typing (MLST) was conducted for serotype VIII and undetermined serotype isolates. Clinical and laboratory data were analyzed to assess trends and mortality risk factors.

Results: A total of 264 episodes of GBS bacteremia were identified, with 147 isolates successfully re-cultured and 125 isolates and patients included in the clinical characteristic analysis. Serotype VIII emerged as the most common serotype (42.1% in 2019-2021) with a significant increase in prevalence over time (P = 0.02). MLST of serotype VIII revealed ST2 as the dominant sequence type (87.8%). Antimicrobial resistance rates for erythromycin, clindamycin, and levofloxacin were 27.2%, 30.4%, and 23.2%, respectively, with notable variability among serotypes. The 30-day mortality rate was 12.8%. Male sex (aOR: 2.18; 95% CI: 1.15-4.13, P = 0.02) and SOFA score (aOR per unit increase: 1.25; 95% CI: 1.12-1.38, P < 0.001) were significantly associated with mortality.

Conclusions: This study highlights the emergence of serotype VIII as a predominant cause of GBS bacteremia and its association with ST2 in South Korea. Male sex and higher SOFA scores were independent risk factors for mortality. The findings emphasize the need for ongoing surveillance and consideration of serotype-specific strategies in clinical management and vaccine development.