Neuroinflammation in Bacterial Meningitis

Under physiologic conditions, the brain is a microbiologically sterile site and is protected from infection by highly specialized barriers, including the hard bony skull, the tough dura mater, and the restrictive blood–brain barrier (BBB). Host defense mechanisms in the central nervous system (CNS) are limited and tightly regulated. Peripheral immune cells and plasma proteins are largely excluded from the brain parenchyma. Once they have breached the protective barriers and entered the CNS, bacteria multiply within the cerebrospinal fluid space (CSF) highly efficiently exhibiting similar kinetics as in vitro and reaching concentrations of up to 109 CFU/mL.