Streptococcal Meningitis

Excerpt

Streptococcal meningitis is a life-threatening infection of the central nervous system (CNS) characterized by acute inflammation of the meninges—the membranous coverings of the brain and spinal cord. This condition is predominantly caused by Streptococcus pneumoniae and Streptococcus agalactiae, both of which are capable of breaching the blood-brain barrier under certain pathological conditions. The CNS is typically a sterile environment, and bacterial invasion into this compartment elicits a robust inflammatory response that can result in significant neurological morbidity and mortality. Anatomical pathways for bacterial entry often involve hematogenous dissemination or direct extension from adjacent infected sites, such as the middle ear or paranasal sinuses.

The natural history of streptococcal meningitis involves initial colonization of mucosal surfaces—commonly the nasopharynx, gastrointestinal tract, or genitourinary tract—followed by translocation into the bloodstream and subsequent penetration of the blood-brain barrier. The pathogenesis varies by age group and immune status: S agalactiae is a predominant cause in neonates, frequently acquired vertically during labor and delivery, while S pneumoniae is more prevalent in older adults and immunocompromised individuals, often following primary respiratory tract infections. Once within the subarachnoid space, the bacterial proliferation and host immune response lead to inflammation, increased intracranial pressure, and potential neuronal injury. Without timely antimicrobial intervention, the disease may progress rapidly, resulting in permanent neurological deficits or death.