Meningitis - Acute, Bacterial Disease Background

Introduction

Meningitis is the infection of the meninges and subarachnoid space that is usually caused by bacteria (eg Haemophilus influenzae type B [Hib], Neisseria meningitidis, Streptococcus pneumoniae, Listeria monocytogenes) and results in high mortality and morbidity throughout the world.

Epidemiology

The epidemiology of meningitis globally is highly dynamic, and changes have been influenced by the widespread use of vaccines, antiretroviral and antibacterial treatment, including preventive methods and improved health care.  Streptococcus pneumoniae remains the most common etiology worldwide and accounts for approximately 25-41% of cases, but distribution of pathogens may vary by region and season. The introduction of conjugated vaccines against Hib, N meningitidis and S pneumoniae has caused a decline in the incidence of bacterial meningitis in children; thus, majority of cases occur in the adult population.

Etiology

Meningitis is usually caused by bacteria such as Haemophilus influenzae type B [Hib], Neisseria meningitidis, Streptococcus pneumoniae, and Listeria monocytogenes. Alternative causes of meningitis include spirochetes (eg Treponema pallidum), mycobacteria (eg Mycobacterium tuberculosis), fungi (eg Cryptococcus, Coccidioides, Sporothrix), viruses (eg herpes simplex virus, varicella zoster virus, cytomegalovirus, enterovirus), protozoa, helminths and malignancy (eg leukemia, lymphoma).

Pathophysiology

The pathogenesis of meningitis primarily occurs through colonization of the nasopharynx with subsequent blood and central nervous system (CNS) invasion, bacteremia due to a localized source (eg infective endocarditis) resulting in CNS invasion, direct entry of organisms into the CNS from a contiguous infection (eg sinuses, mastoid) and by trauma or cerebrospinal fluid (СЅF) leak.

Meningitis - Acute, Bacterial_Disease Background

Risk Factors

The causative agents depend on the age of the patient and predisposing factors such as a compromised immune system, liver disease, alcoholism, uncontrolled diabetes, pregnancy, living in dormitories/military barracks and jail.