Genomic epidemiology of GBS in Lithuania

Streptococcus agalactiae (Group B streptococcus, GBS) is a leading cause of neonatal infections. Detailed assessment of GBS genetic and phenotypic factors associated with GBS carriage, mother-to-baby transmission, and GBS infection in neonates and adults is still lacking. Ultimately, understanding the distribution of GBS serotypes, genotypes and virulence factors will aid in estimating potential GBS vaccine effectiveness on different types of GBS disease. Information on GBS genotypes is currently lacking from Lithuania, hence, we set out to characterise GBS isolates collected from pregnant and non-pregnant women in Kaunas region in Lithuania. Whole genome sequences of 42 GBS isolates were analysed to determine multi-locus sequence typing (MLST), presence of acquired antimicrobial resistance and surface protein genes, and phylogenetic relatedness of isolates. We identified serotypes Ia (42.9%, n=18), III (33.3%, n=14), V (21.4%, n=9); and a single isolate of serotype Ib in the dataset. Genomic analysis revealed high diversity among GBS isolates with 18 sequence types (STs) identified, including three novel STs. 85.7% (n=36) of isolates had at least one antimicrobial resistance gene: tetM or tetO (n=35), ermB or lsaC (n=8), and ant6-Ia and aph3-III (n=2). This report represents the first genomic analysis of a GBS population isolated from women in Lithuania. This information is pivotal to better understand global spread of GBS genotypes and antimicrobial resistance patterns and will aid as basis for future GBS research in Lithuania and globally.