McGee L, Chochua S, Li Z, et al. - Given the leading causative role of Group B Streptococcus (GBS) in neonatal sepsis and meningitis and an important causative role in invasive infections in pregnant and nonpregnant adults, researchers here sought to characterize 6,340 invasive GBS recovered during 2015-2017 through population-based Active Bacterial Core surveillance in eight states utilizing whole-genome sequencing, a validated bioinformatics pipeline, and targeted antimicrobial susceptibility testing. Outcomes revealed that nearly 98.4% of isolates fall in six serotypes (21.8% Ia, 17.6% V, 17.1% II, 15.6% III, 14.5% Ib, 11.8% IV). Most (94.2%) isolates were in eleven clonal complexes (CCs) involving multilocus sequence types identical or closely related to STs 1, 8, 12, 17, 19, 22, 23, 28, 88, 452 and 459. Point mutations within pbp2x were detected in 54 isolates (0.87%) in association with non-susceptibility to one or more β-lactam antibiotics. Fifty-six percent of isolates exhibited genes conversing resistance to macrolides and/or lincosamides; 85.2% of isolates had tetracycline resistance genes. Vancomycin-nonsusceptibility (MIC 2µg/ml) was observed in two isolates that carried vanG. They detected capsule genes, 1-2 of the three main pilus gene clusters, and one of four homologous Alpha/Rib family determinants in nearly all isolates. Primarily serotype III/CC17 isolates (465 isolates) exhibited the presence of hvgA virulence gene, but there were 8 exceptions (7 IV/CC452 and 1 IV/CC17). This first comprehensive, population-based quantitation of strain features in the United States emphasizes the necessity for good coverage for the current vaccine candidates. Although beta-lactams remain relevant for first-line treatment and prophylaxis, the rise of nonsusceptibility warrants ongoing monitoring.