Meningitis is associated with high mortality and frequently causes severe sequelae. Newborn infants are particularly susceptible to this type of infection; they develop meningitis 30 times more often than the general population. Group B streptococcus (GBS) bacteria are the most common cause of neonatal meningitis, but they are rarely responsible for disease in adults. Scientists from the Institut Pasteur, in collaboration with Inserm, Université de Paris and Necker-Enfants Malades Hospital (AP-HP), set out to explain neonatal susceptibility to GBS meningitis. In a mouse model, they demonstrated that the immaturity of both the gut microbiota and epithelial barriers such as the gut and choroid plexus play a role in the susceptibility of newborn infants to bacterial meningitis caused by GBS. The findings were published in the journal Cell Reports on June 29, 2021.