Desiccation stress enhances virulence potential of group B Streptococcus

Streptococcus agalactiae (Group B Streptococcus, GBS) asymptomatically inhabits the gastrointestinal and female reproductive tracts but can also cause invasive diseases in susceptible individuals. Despite its clinical importance, relatively little is known about its ability to survive outside the host and whether environmental persistence contributes to transmission and infection. Here we investigate the GBS survival under nutrient starvation and desiccation, characterizing phenotypic and genomic adaptations associated with environmental persistence. GBS remained viable for 30 days during starvation at room temperature and for more than 80 days under desiccated conditions, with GBS grown to stationary-phase bacteria exhibiting greater survival than actively growing bacteria. Survival under desiccation was conserved among several clinically relevant GBS serotypes. Following rehydration desiccated GBS exhibited enhanced biofilm formation compared to control non-desiccated strains. Whole-genome sequencing identified mutations in genes involved in capsule biosynthesis, cell-envelope homeostasis, nutrient transport, and carbohydrate metabolism, suggesting that multiple adaptive pathways may contribute to environmental persistence. Importantly, desiccated GBS retained the capacity to colonize the vaginal mucosa and displayed increased invasion of reproductive tissues in a murine vaginal colonization model. In a systemic infection model, desiccated GBS exhibited enhanced virulence compared to control non-desiccated GBS, demonstrating that environmental survival does not diminish pathogenic potential. This environmental persistence may represent an underappreciated factor contributing to GBS transmission and the epidemiology of late-onset neonatal disease.