The blood brain barrier (BBB) is a highly dynamic structure and consistsof endothelial cells, which are characterized by the presence of tight junctions and relative lack ofendocytic vesicles. The tight junctions are reinforced by the foot processes of the astrocytes. The BBBfunctions through these specialised structures, to maintain the environment of the brain in a steadystate by regulating the influx and efflux of substances. The protective effect of the BBB is however,lost during bacterial and viral infections. The primary mechanism operative are an increase in the permeabilityof the BBB and/or direct invasion of the brain by microorganisms. Since the BBB is relatively impermeableto chemotherapeutic agents the treatment of CNS infections is difficult. This paper aims to examine thevarious mechanisms by which infection spreads to the brain, and suggest measures for successful drugdelivery into the brain during infections.

Keywords: Anti-Infective Agents, Biological Markers, Biological Transport, Active, Blood-Brain Barrier, Central Nervous System Infections, Models, Biological, Permeability, Pinocytosis, Tight Junctions