The increasing burden of group B from 2013 to 2023: a retrospective cohort study in Beijing, China.

Group B (GBS) is a leading pathogen responsible for fatal infections in newborns primarily due to vertical transmission from colonized mothers. Cases of invasive GBS infections in adults have also increased and attracted attention recently. To comprehensively understand the evolving burden of vaginal GBS carriage in pregnant and non-pregnant women, as well as the trends in invasive GBS diseases and antibiotic resistance in China, we conducted a retrospective study using data from a large tertiary hospital in Beijing from 2013 to 2023. Over the past decade, improvements in GBS screening methods for pregnant women have significantly increased the GBS recovery rate. The detection rate of GBS and its proportion among vaginal pathogens have shown a gradual increase in GBS colonization in both pregnant and non-pregnant women. An analysis of vaginal pathogen composition revealed variations in GBS prevalence across different age groups, as well as a potential competitive relationship between GBS and in the vaginal environment. Additionally, we analyzed 165 invasive GBS cases, including three in newborns. The incidence of invasive GBS cases has risen since 2016, particularly among individuals over the age of 40. The 5,858 GBS isolates exhibited notably high resistance rates to erythromycin (72.2%), clindamycin (60%), and levofloxacin (50.1%), with 30.8% classified as multidrug-resistant. Importantly, invasive GBS strains exhibited a higher resistance rate to levofloxacin (61.2%) compared to colonizing strains (49.8%). This study highlights the importance of continuous screening and monitoring for GBS, especially given the concerning antibiotic resistance rates of GBS.IMPORTANCEGroup B (GBS) is an important pathogen that commonly causes infections in newborns and the elderly. This retrospective study provides a comprehensive analysis of GBS strains isolated from a large tertiary hospital in Beijing between 2013 and 2023, revealing an increasing colonization rate of GBS in both pregnant and non-pregnant women. Analysis of vaginal pathogens indicates a growing proportion of GBS among vaginal pathogens. Additionally, the high resistance rates of GBS to erythromycin, clindamycin, and levofloxacin, as well as the prevalence of multidrug resistance, are issues that merit attention. We also examined the differences in resistance rates of GBS strains from various sample types, finding that the levofloxacin resistance rate in GBS strains causing invasive infections was significantly higher than in colonizing strains. This study provides new data and insights for clinical research on GBS.