Genomic epidemiology of group B streptococci spanning 10 years in an Irish maternity hospital, 2008–2017

•Genomic epidemiological analysis of Group B streptococcal isolates was performed using the S. agalactiae PubMLST database. •CgMLST discriminated same sequence type and, identified known and suspected case clusters. •Isolates clonal complex (CC) 17, CC23 CC19 were most common in infant, maternal non-invasive cases, respectively. •Erythromycin clindamycin resistance associated with CC1, erm(B) increased over study period. •Genome gene-by-gene approach implemented on a public database will facilitate GBS surveillance. Objectives The genomic epidemiology group b (GBS) from Rotunda maternity hospital, Dublin, 2008–2017, investigated. Methods Whole genome sequences (invasive, n = 114; non-invasive, 76) infants women analysed (https://pubmlst.org/sagalactiae/). Results Serotypes III (36%), Ia (18%), V (17%), II (11%) Ib, (9%) types (ST) 17 (23%), ST-23 (14%), ST-1 (12%) ST-19 (7%) common. Core MLST (cgMLST) differentiated ST, grouped STs into five lineages congruent complexes mother-baby pairs linked infant cases. Clonal accounted for 40% 22% invasive respectively 21% isolates. disease (30%) carriage (24%), Erythromycin (26%) (18%) period presence gene (55%), CC1 (33%) (24%). A multi-resistant integrative conjugative element incorporated PI-1 locus detected CC17, an ST-12 isolate confirming global dissemination this element. All possessed one or more pilus islands. Genes encoding other potential protective proteins including Sip, C5a peptidase Srr1 present 100%, 99.5% 65.8% isolates, srr2 unique to CC17. Conclusions PubMLST.org website provides valuable framework surveillance inform local epidemiology, preventive control measures.