What is meningococcal meningitis?

Definition

Meningococcal meningitis (MM) is an invasive bacterial form of meningitis,
an infection that causes swelling and
inflammation of the thin lining (membrane) that surrounds the brain
and spinal cord. MM, which can cause severe brain damage and is fatal if
untreated, was first described clinically in 1805 in Switzerland following an
outbreak in Geneva.

Causes

MM is caused by several different bacteria, including Neisseria
meningitidis, a gram-negative diplococcus bacterium found exclusively
in humans. A minimum of thirteen different serogroups of N.
meningitidis have been identified, based on the capsular
polysaccharide. Serogroups A, B, and C have been recognized as significant causes
of meningococcal disease.

Risk Factors

Risk factors for the invasive disease may be a combination of host,
environment, and organism strain. Recent respiratory tract infection, low
socioeconomic status, and a susceptible population increase vulnerability.
Climatic factors also influence seasonal outbreaks. In Africa, epidemics
begin during the dry season; in temperate countries, sporadic illness and
epidemics appear during the late winter and early spring.

MM is spread through direct contact with respiratory droplets of infected people. Therefore, it can be spread through close and prolonged contact with others, through sneezing or coughing, and by living close to an infected person.

Symptoms

The clinical manifestations of meningococcal disease can be quite varied,
ranging from transient fever and the presence of bacteria in the blood
(bacteremia) to fulminate disease and death occurring within
hours of clinical onset. Symptoms include intense headache, fever, nausea,
vomiting, photophobia, stiff neck, lethargy, myalgia, and a characteristic
petechial rash.

Screening and Diagnosis

MM is difficult to diagnose outside epidemics because symptoms mimic many other illnesses. Initial diagnosis can be made by clinical examination followed by a lumbar puncture showing a purulent spinal fluid. The bacteria can sometimes be seen in microscopic examinations of the spinal fluid.

Treatment and Therapy

Antimicrobial chemoprophylaxis is the primary means of preventing transmission
of invasive meningococcal disease from patients to close contacts. The
identification of the N. meningitidis serogroups and their
susceptibility test to antibiotics are important for treatment
and for control measures. A range of antibiotics, including penicillin,
ampicillin, chloramphenicol, and ceftriaxone, can treat the infection.

Prevention and Outcomes

Several surveillance data conclude that immunization with a meningococcal
vaccine offers the best intervention strategy. Routine
vaccination is also recommended for high-risk groups, including college freshmen
living in dormitories, travelers, populations experiencing outbreaks of
meningococcal disease, and persons with increased susceptibility.

There are three types of effective and safe vaccines for preventing MM: meningococcal polysaccharide vaccines, as either bivalent (groups A and C), trivalent (groups A, C, and W), or tetravalent (groups A, C, Y, and W-135); outer membrane proteins against serogroup B; and meningococcal conjugate vaccines against group C and a tetravalent A, C, Y, and W-135 conjugate vaccine.

Bibliography

Centers for Disease Control and Prevention. “Meningococcal Disease.” Available at http://www.cdc.gov.

Klein, D. L., and R. W. Ellis. “Conjugate Vaccines Against Streptococcus pneumoniae.” In New Generation Vaccines, edited by M. M. Levine at al. 2d ed. New York: Marcel Dekker, 1997.

Kvalsvig, A. J., and D. J. Unsworth. “The Immunopathogenesis of Meningococcal Disease.” Journal of Clinical Pathology 56 (2003): 417-422.

Pollard, A. J. “Global Epidemiology of Meningococcal Disease and Vaccine Efficacy.” Pediatric Infectious Disease Journal 23 (2004): S274-S279.

World Health Organization. Control of Epidemic Meningococcal Disease. 2d ed. Geneva: Author, 1998.