Molecular characterization, antimicrobial resistance and invasion of epithelial cells by Streptococcus agalactiae strains isolated from colonized pregnant women and newborns in Rio de Janeiro, Brazil.

This article focuses on the prevalence, molecular characteristics, antimicrobial susceptibility, and epithelial invasion capacity of *Streptococcus agalactiae* strains isolated from pregnant women and newborns in Rio de Janeiro, Brazil. Among 67 isolates analyzed, capsular types Ia and V were most common, with multilocus sequence typing revealing 19 sequence types grouped into six clonal complexes, predominantly CC17 and CC23. All isolates carried the virulence genes *lmb* and *iag*, and some strains demonstrated the ability to adhere to and invade human respiratory epithelial cells. High resistance rates were observed for tetracycline (85%), erythromycin (70.8%), and clindamycin (58.3%), with 6% of isolates classified as multidrug resistant; however, all isolates remained susceptible to penicillin. The study underscores the genetic diversity and antimicrobial resistance of *S. agalactiae* in this population and highlights the need for ongoing surveillance to inform prevention and treatment strategies in pregnant women and neonates.