Perinatal Streptococcus agalactiae Epidemiology and Surveillance Targets

Abstract

Streptococcus agalactiae, or group B streptococcus (GBS), is a major neonatal pathogen. Recent data have elucidated the global prevalence of maternal and neonatal colonization, but gaps still remain in the epidemiology of this species. A number of phenotypic and genotypic classifications can be used to identify the diversity of GBS strains, and some are more discriminatory than others. This review explores the main schemes used for GBS epidemiology and further details the targets for epidemiological surveillance. Current screening practices across the world provide a unique opportunity to gain detailed information on maternal colonizing strains and neonatal disease-causing strains, which is vital for monitoring and therapeutics, if sufficient detail can be extracted. Deciphering which isolates are circulating within specific populations and recording targets within invasive strains are crucial steps in monitoring the implementation of therapeutics, such as vaccines, as well as developing novel therapies against prevalent GBS strains. Having a detailed understanding of global GBS epidemiology will prove invaluable for understanding the pathogenesis of this organism and equipping future prevention strategies for success.

Keywords: Streptococcus agalactiae; clonal complex; epidemiology; group B streptococcus; immunization; perinatal infections; sequence type; serotype; surveillance; vaccine.

FIG 1

Frequencies of the 12 most prevalent GBS sequence types available from the MLST database, which includes a total of 635 sequence types (remaining STs account for <1% each).

FIG 2

Contributions by continent of GBS isolates available in the MLST database, as percentages of all isolates (South America represents 0.1% and is therefore not visible).

FIG 3

Serotype distribution within each sequence type, using the public MLST database for GBS, for the 12 most represented sequence types within the database, as well as their corresponding clonal complexes (CCs), where appropriate.