Meningococci (Neisseria meningitidis) cause meningitis and meningococcemia. 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.
(See also Introduction to Neisseriaceae.)
Meningococci are gram-negative aerobic cocci that belong to the family Neisseriaceae. There are 13 serogroups; 5 (serogroups A, B, C, W135, and Y) cause most human disease.
Worldwide, the incidence of endemic meningococcal disease is 0.5 to 5/100,000, with an increased number of cases during 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 (which were often caused by serogroup A), attack rates ranged from 100 to 800/100,000. After widespread use of the meningococcal A vaccine in the African meningitis belt, serogroup A has been replaced by other meningococcal serogroups and by Streptococcus pneumoniae.
In the US, the annual incidence ranges from 0.5 to 1.1/100,000. Over the past 20 yr, incidence of meningococcal disease has declined annually. Most cases are sporadic, typically in children < 2 yr; < 2% occur in outbreaks. Outbreaks tend to occur in semiclosed communities (eg, military recruit camps, college dormitories, schools, day-care centers) and often involve patients aged 5 to 19 yr. Serogroups B, C, and Y are the most frequent causes of disease in the US; each serogroup accounts for about one third of reported cases. Serogroup A is rare in the US.
Meningococci can colonize the nasopharynx of asymptomatic carriers. A combination of factors is probably responsible for transition from carrier state to invasive disease. Despite documented high rates of colonization (10 to 40% of healthy people), transition to invasive disease is rare and occurs primarily in previously uninfected patients. Transmission usually occurs via direct contact with respiratory secretions from a nasopharyngeal carrier. Nasopharyngeal carriage rates are highest in adolescents and young adults, who serve as reservoirs for transmission of N. meningitidis. Carrier rates rise dramatically during epidemics.
After invading the body, N. meningitidis causes meningitis and severe bacteremia in children and adults, resulting in profound vascular effects. Infection can rapidly become fulminant. The case-fatality rate is 4 to 6% for meningitis alone, compared with up to 40% for meningococcemia with septic shock. Of patients who recover, 10 to 15% have serious sequelae, such as permanent hearing loss, intellectual disability, or loss of phalanges or limbs.
The most frequently infected are
Other high-risk groups include
College freshmen living in dormitories
Travelers to places where meningococcal disease is common (eg, certain countries in Africa and in Saudi Arabia during the Hajj)
People with functional or anatomic asplenia or complement deficiencies
Microbiologists working with N. meningitidis isolates
Infection or vaccination confers serogroup-specific immunity.
Incidence of meningococcal disease is higher in people with AIDS than in the general adult population. Antecedent viral infection, household crowding, chronic underlying illness, and both active and passive smoking are associated with increased risk of meningococcal disease (1).
Patients with meningitis frequently report fever, headache, and stiff neck (see Acute Bacterial Meningitis). Other symptoms include nausea, vomiting, photophobia, and lethargy. A maculopapular or hemorrhagic petechial rash often appears soon after disease onset. Meningeal signs are often apparent during physical examination.
Fulminant meningococcemia syndromes include Waterhouse-Friderichsen syndrome (septicemia, profound shock, cutaneous purpura, adrenal hemorrhage), sepsis with multiple organ failure, shock, and disseminated intravascular coagulation. A rare, chronic meningococcemia causes recurrent mild symptoms (mostly joint and cutaneous).
Neisseria are small, gram-negative cocci readily identified with Gram stain and by other standard bacteriologic identification methods. Serologic methods, such as latex agglutination and coagglutination tests, allow 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 testing of CSF, blood, and other normally sterile sites for N. meningitidis is more sensitive and specific than culture and may be useful when prior antibiotic administration interferes with isolating the organism.
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, ceftriaxone 2 g IV q 12 h) plus vancomycin 30 to 60 mg/kg IV q 8 to 12 h.. In immunocompromised patients and patients > 50 yr, coverage for Listeria monocytogenes should be considered by adding ampicillin 2 g IV q 4 h.
Once N. meningitidis has been definitively identified, the preferred treatment is ceftriaxone 2 g IV q 12 h or penicillin 4 million units IV q 4 h.
Corticosteroids decrease the incidence of neurologic complications in children and adults. When corticosteroids are used, they should be given with or before the first 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 of acquiring disease and should receive a prophylactic antibiotic. Options include
Azithromycin is not routinely recommended, but a recent study showed that a single 500-mg dose was equivalent to rifampin for chemoprophylaxis and so could be an alternative for patients with contraindications to recommended drugs.
Ciprofloxacin-resistant meningococcal disease has been reported in several countries (Greece, England, Wales, Australia, Spain, Argentina, France, India). More recently, 2 US states (North Dakota, Minnesota) reported ciprofloxacin-resistant meningococci and so recommended that ciprofloxacin chemoprophylaxis not be used as preventive treatment for people who have had close contact with someone diagnosed with meningococcal disease.
Several meningococcal vaccines are available in the US (see Meningococcal Disease: Recommendations of the Advisory Committee on Immunization Practices). Available vaccines include
2 quadrivalent conjugate vaccines (MenACWY-D and MenACWY-CRM) that protect against 4 of the 5 common pathogenic serogroups of meningococcus (all but B)
A bivalent conjugate vaccine that protects against serogroups C and Y and that is available only in combination with a Haemophilus influenzae type b vaccine (Hib-MenCY)
A quadrivalent polysaccharide vaccine (MPSV4) for use in patients ≥ 56 yr
2 recombinant vaccines against serogroup B (MenB)
All children should receive MenACWY-D or MenACWY-CRM at age 11 to 12 yr, with a booster dose at age 16 yr. Vaccination is also recommended for people who are aged 19 to 55 and at risk, including military recruits, college freshmen living in a dormitory, travelers to hyperendemic or epidemic areas (a booster dose is given to those whose last vaccination was ≥ 5 yr before), and people with laboratory or industrial exposure to N. meningitidis aerosols. Adults with functional asplenia or persistent complement component deficiencies and patients with HIV infection (not a routine vaccination unless other risk factors are present) should receive 2 doses of MenACWY-D or MenACWY-CRM at least 2 mo apart.
At-risk people ≥ 56 yr should receive the MPSV4 polysaccharide vaccine. However, in this age group, MenACWY is preferred for the following people:
MenB (2-dose series at least 1 mo apart or 3-dose vaccine at 0, 2, and 6 mo) is recommended for people ≥ 10 yr who are at increased risk of serogroup B meningococcal disease.
Children < 11 yr are not routinely vaccinated, but those at high risk should receive Hib-MenCY, MenACWY-D, or MenACWY-CRM. Vaccine selection varies with age and risk factors (see CDC Vaccination Schedule Birth Through 18 Yr).
Over 90% of meningococcal infections involve meningitis or septicemia.
An asymptomatic nasopharyngeal carrier state is common; transmission usually occurs via direct contact with respiratory secretions from a carrier.
Most cases are sporadic, typically in children < 2 yr, but outbreaks can occur, primarily in semiclosed communities (eg, military recruit camps, dormitories, day-care centers) and often involve patients aged 5 to 19 yr.
Treat with ceftriaxone or penicillin; add dexamethasone for patients with meningitis.
Give close contacts a prophylactic antibiotic; options include rifampin, ceftriaxone, and a fluoroquinolone.
Vaccinate all children starting at age 11 to 12 yr, and selectively vaccinate high-risk younger children and other high-risk people.