In this article, we will discuss the Pathogenesis of Bacterial Meningitis (Nontubercular). So, let’s get started.
S.pneumoniae is the most common pathogens in children and adults in USA and other developed countries. In India, meningococcal meningitidis is the most common cause of bacterial meningitis.
S.pneumoniae, N.meningitidis and H.influenzae are transmitted by air-borne route by droplets or exchange of saliva. These bacteria initially colonise the nasopharynx, attach to the mucosal epithelial cells, secrete IgA protease enzymes that breakdown the protective mucosal layer to enter into the blood stream producing bacteremia. From the blood they reach to CSF by breaching the blood-brain barrier. Once the bacteria reach the CSF, they have an excellent chance of survival and multiplication because humoral defence mechanism depending on the immunoglobulin and complement activity is absent. However, bacterial meningitis can occur by hematogenous spread or through congenital neuroectodermal defects, craniotomy sites, middle ear, dental and sinus infection, and skull fractures.
Rarely, intracerebral abscess may rupture into the ventricle or subarachnoid space producing meningitis.
The lysis of bacteria with release of their cell wall components into subarachnoid space incite inflammatory response and the formation of purulent exudate in CSF. The inflammatory response is mediated by cytokines and chemokines. The inflammation of cerebral vessels (vasculitis) produces ischemia, infarction, thrombosis and thrombophlebitis of cortical veins resulting in cerebral edema, raised ICT and coma.