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Meningococcus
(Neisseria meningitidis) causes
meningitis and septicemia. Symptoms, usually severe, include headache,
nausea, vomiting, photophobia, lethargy, rash, multiple organ failure,
shock, and disseminated intravascular coagulation. Diagnosis is
clinical, confirmed by culture. Treatment is penicillin or a 3rd-generation
cephalosporin.
Meningitis and septicemia account for > 90% of meningococcal infections. Infections of lungs, joints, respiratory passageways, GU organs, eyes, endocardium, and pericardium are less common.
Worldwide, the incidence of endemic disease is 0.5 to 5/100,000, with an increased number of cases in winter and spring in temperate climates. Local outbreaks occur, most frequently in sub-Saharan Africa between Senegal and Ethiopia, an area known as the meningitis belt. In major African epidemics, attack rates range from 100 to 800/100,000 population.
Meningococci can colonize the oropharynx/nasopharynx of asymptomatic carriers. A combination of factors is probably responsible for transition from carrier to invasive disease. Despite documented high rates of colonization, transition to invasive disease is rare and occurs primarily in previously uninfected patients. Transmission generally occurs via direct contact with respiratory secretions from a nasopharyngeal carrier. Carrier rates rise dramatically during epidemics.
After invading the body, N. meningitidis causes meningitis and severe bacteremia in both children and adults, resulting in profound vascular effects. Infection can rapidly become fulminant and is associated with a mortality rate of 10 to 15%. Of patients who recover, 10 to 15% have serious sequelae, such as permanent hearing loss, mental retardation, or loss of phalanges or limbs.
Children between 6 mo and 3 yr are the most frequently infected. Other high-risk groups include adolescents, military recruits, college freshmen living in dormitories, people with complement deficiencies, and microbiologists working with N. meningitidis isolates. Infection or vaccination confers type-specific immunity.
Symptoms and Signs
Patients with meningitis frequently report fever, headache, and stiff neck (see Meningitis: Acute Bacterial Meningitis). Other symptoms include nausea, vomiting, photophobia, and lethargy. A maculopapular or hemorrhagic peticial rash often appears soon after disease onset. Meningeal signs are often apparent on physical examination. Fulminant meningococcemia syndromes include Waterhouse-Friderichsen syndrome (septicemia, profound shock, cutaneous purpura, and adrenal hemorrhage), sepsis with multiple organ failure, shock, and disseminated intravascular coagulation. A rare, chronic meningococcemia causes recurrent mild symptoms.
Diagnosis
Neisseria are small, gram-negative cocci readily identified on Gram stain and by other standard bacteriologic identification methods. Serologic methods, such as latex agglutination and coagglutination tests, permit rapid presumptive diagnosis of N. meningitides in blood, CSF, synovial fluid, and urine. However, both positive and negative results should be confirmed by culture. PCR for N. meningitidis has been developed but is not commercially available.
Treatment
and Prevention
While awaiting definitive identification of the causal organism, immunocompetent adults suspected of having meningococcal infection are given a 3rd-generation cephalosporin (eg, cefotaxime 2 g IV q 6 h or ceftriaxone 2 g IV q 12 h plus vancomycin 500 mg IV q 6 h or 1 g IV q 12 h). Coverage for Listeria monocytogenes should be considered in immunocompromised patients by adding ampicillin 2 g IV q 4 h. Once N. meningitidis has been definitively identified, the preferred treatment is penicillin 4 million units IV q 4 h.
Corticosteroids decrease the incidence of neurologic complications in children. When corticosteroids are used, they should be administered with or before the 1st dose of antibiotics. Dexamethasone 0.15 mg/kg IV q 6 h in children (10 mg q 6 h in adults) is given for 4 days.
Close contacts of people with meningococcal disease are at increased risk for acquiring disease and should receive a prophylactic antibiotic. Options include rifampin 600 mg po q 12 h for 4 doses (children > 1 mo, 10 mg/kg po q 12 h for 4 doses; children < 1 mo, 5 mg/kg po q 12 h for 4 doses) or ceftriaxone 250 mg IM for 1 dose (children < 15 yr, 125 mg IM for 1 dose) or a single dose of a fluoroquinolone in adults ( ciprofloxacin or levofloxacin 500 mg or ofloxacin 400 mg).
A meningococcal conjugate vaccine is available in the US. The vaccine includes 4 of the 5 serogroups of meningococcus (all but B). People who are at increased risk for developing meningococcal infection should be vaccinated. Vaccination is recommended for military recruits, travelers to endemic areas, people with laboratory or industrial exposure to N. meningitidis aerosols, and patients with functional or actual asplenia. Vaccination should be considered for college freshmen, especially those who live in dormitories, household or institutional contacts of people with meningococcal disease, medical and laboratory personnel at risk of exposure to meningococcal disease, and patients with immune deficiencies.
Last full review/revision November 2005
Content last modified November 2005
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