Maternal Colonization With Group B Streptococcus and Serotype Distribution Worldwide: Systematic Review and Meta-analyses

Abstract

Background.Maternal rectovaginal colonization with group B Streptococcus (GBS) is the most common pathway for GBS disease in mother, fetus, and newborn.This article, the second in a series estimating the burden of GBS, aims to determine the prevalence and serotype distribution of GBS colonizing pregnant women worldwide. Methods.We conducted systematic literature reviews (PubMed/Medline, Embase, Latin American and Caribbean Health Sciences Literature [LILACS], World Health Organization Library Information System [WHOLIS], and Scopus), organized Chinese language searches, and sought unpublished data from investigator groups.We applied broad inclusion criteria to maximize data inputs, particularly from low-and middle-income contexts, and then applied new meta-analyses to adjust for studies with less-sensitive sampling and laboratory techniques.We undertook meta-analyses to derive pooled estimates of maternal GBS colonization prevalence at national and regional levels.Results.The dataset regarding colonization included 390 articles, 85 countries, and a total of 299 924 pregnant women.Our adjusted estimate for maternal GBS colonization worldwide was 18% (95% confidence interval [CI], 17%-19%), with regional variation (11%-35%), and lower prevalence in Southern Asia (12.5% [95% CI, 10%-15%]) and Eastern Asia (11% [95% CI, 10%-12%]).Bacterial serotypes I-V account for 98% of identified colonizing GBS isolates worldwide.Serotype III, associated with invasive disease, accounts for 25% (95% CI, 23%-28%), but is less frequent in some South American and Asian countries.Serotypes VI-IX are more common in Asia.Conclusions.GBS colonizes pregnant women worldwide, but prevalence and serotype distribution vary, even after adjusting for laboratory methods.Lower GBS maternal colonization prevalence, with less serotype III, may help to explain lower GBS disease incidence in regions such as Asia.High prevalence worldwide, and more serotype data, are relevant to prevention efforts.Keywords.group B Streptococcus; colonization; vaginal; pregnancy; serotypes.Group B Streptococcus (GBS; Streptococcus agalactiae) via maternal rectovaginal colonization, causes a spectrum of disease including maternal infection, stillbirth, and early-and late-onset sepsis in newborns, and may contribute to preterm delivery and hypoxic ischemic encephalopathy [1].Thus, ascertaining the worldwide prevalence and serotype distribution of GBS colonizing the rectovaginal tracts of pregnant women is critical [2][3][4].There may be true differences in GBS maternal colonization prevalence, with variation reported by region [5], ethnicity, and socioeconomic status [6].However, some of this variation may be due to methodological issues, such as time of GBS screening (during pregnancy or at delivery [7]), sampling site (in particular, whether rectal samples were performed [8-11]), and laboratory culture techniques, notably use of selective enrichment broth [12].There is no established international standard for sampling for maternal GBS colonization; however, the recommendation by the Centers for Disease Control and Prevention