Meningococci are gram-negative aerobic cocci that belong to the family Neisseriaceae. There are 13 serogroups; 6 serogroups (A, B, C, W135, X, 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 Gambia and Senegal in the west and Ethiopia, Eritrea, and northern Kenya in the east; this area is known as the sub-Saharan (African) meningitis belt, which includes 26 countries. In major African epidemics (which were often caused by serogroup A), attack rates ranged from 100 to 800/100,000 and affected up to 200,000 people each year. After widespread use of the meningococcal A vaccine in the African meningitis belt, serogroup A has been replaced by other meningococcal serogroups and by Streptococcus pneumoniae.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 0.12 to 1.1/100,000. Over the past 20 years, incidence of meningococcal disease has declined annually. Most cases are sporadic, typically in children < 2 years of age; < 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 years. 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.
Diseases Caused by Meningococci
Over 90% of meningococcal infections involve
Infections of lungs, joints, respiratory passageways, genitourinary organs, eyes, endocardium, and pericardium are less common.
N. meningitidis has been reported to cause urethritis, but, recently, incidence of meningococcal urethritis has been increasing in heterosexual men and in men who have sex with men. These men frequently reported oral sex; N. meningitidis colonizes the nasopharynx. N. meningitidis may also cause proctitis, primarily in men who have sex with men.
Pathophysiology
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 (5 to 40% of healthy people), which may be transient, brief, or prolonged, transition to invasive disease is rare (< 1%) and occurs primarily in previously uninfected patients. Transmission usually occurs via direct contact with respiratory secretions or by inhalation of large-droplet nuclei 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 20% have serious sequelae, such as permanent hearing loss, intellectual disability, or loss of phalanges or limbs.
Risk factors
The most frequently infected are
Other high-risk groups include
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Adolescents
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Military recruits
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College freshmen living in dormitories
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Travelers to places where meningococcal disease is common (eg, certain countries in Africa and in Saudi Arabia during the Hajj)
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People with functional or anatomic asplenia or a complement deficiency
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People treated with eculizumab or ravulizumab
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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).
Pathophysiology reference
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1. Advisory Committee on Immunization Practices: Prevention and control of meningococcal disease recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 62(2):1–28, 2013.
Symptoms and Signs
Patients with meningitis frequently report fever, headache, and stiff neck. 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).
Fulminant meningococcemia initially causes petechiae, which become confluent and rapidly progress to ecchymoses.
Petechiae and purpura are visible on the child's face. Hemorrhagic return from the nasogastric tube is consistent with disseminated intravascular coagulation, also secondary to meningococcemia.
Petechiae and purpura secondary to meningococcemia are widespread. Lesions tend to be common on the trunk and lower extremities.
Petechiae are isolated in some areas and coalescent, and developing necrosis in other areas (left). A large area of necrosis is seen (right).
Diagnosis
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. meningitidis in blood, cerebrospinal fluid, synovial fluid, and urine. However, both positive and negative results should be confirmed by culture.
Polymerase chain reaction testing of cerebrospinal fluid, 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.
Treatment
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 every 6 hours, ceftriaxone 2 g IV every 12 hours) or meropenem (2 g IV every 8 hours) plus vancomycin 30 to 60 mg/kg IV every 8 to 12 hours. In immunocompromised patients and patients > 50 years, coverage for Listeria monocytogenes should be considered by adding ampicillin 2 g IV every 4 hours. The fluoroquinolone antibiotic, moxifloxacin, is an alternative in patients allergic to penicillin and cephalosporins.
Once N. meningitidis has been definitively identified, the preferred treatment is one of the following:
In many countries, penicillin G is still the first-choice for invasive meningococcal disease. However, because many countries, including the US, have increasing incidence of isolates with reduced susceptibility to penicillin, those countries typically give initial treatment with a 3rd-generation cephalosporin, such as ceftriaxone or cefotaxime. Also, when penicillin is used, follow-up treatment with ceftriaxone, ciprofloxacin, or rifampin is necessary to eliminate nasopharyngeal carriage. Recently, 2 isolates in Costa Rica and 6 in India have been reported to be resistant to both penicillin and 3rd-generation cephalosporins.
Corticosteroids decrease the incidence of neurologic complications in children and adults with suspected bacterial meningitis due to Haemophilus influenzae type b or S. pneumoniae. The evidence is less clear when N. meningitidis is the cause. However, high-dose corticosteroids worsen the outcome in meningococcal shock without meningitis and should not be used in such cases; however, low-dose corticosteroids can be used in patients with inadequate adrenal function. When corticosteroids are used, they should be given with or before the first dose of antibiotics. Dexamethasone 0.15 mg/kg IV every 6 hours in children (10 mg every 6 hours in adults) is given for 4 days.
Prevention
Antibiotic prophylaxis
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 is rare but has been reported in several countries (Greece, England, Wales, Australia, Spain, Argentina, France, India) and in 2 US states (North Dakota, Minnesota). When choosing an antibiotic for postexposure prophylaxis, clinicians should consider reports of local ciprofloxacin-resistant meningococci.
Vaccination
See Meningococcal Vaccine for more information, including indications, contraindications and precautions, dosing and administration, and adverse effects. See also the vaccine schedules for children and adults from the Centers for Disease Control and Prevention (CDC) and meningococcal vaccine recommendations from the Advisory Committee on Immunization Practices (ACIP).
There are several meningococcal vaccines:
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2 quadrivalent conjugate vaccines (MenACWY-D and MenACWY-CRM) that protect against 4 of the 6 common pathogenic serogroups of meningococcus (all but B and X)
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A bivalent conjugate vaccine that protects against serogroups C and Y that is available only in combination with tetanus toxoid and Haemophilus influenzae type b vaccine (Hib-MenCY-TT) is available for infants at increased risk of meningococcal disease (see also infant meningococcal vaccination recommendations from the ACIP)
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A quadrivalent polysaccharide vaccine (MPSV4) for use in selected patients ≥ 56 years
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2 monovalent vaccines against serogroup B (MenB-4C and MenB-FHbp)
All children should receive MenACWY-D or MenACWY-CRM at age 11 or 12 years, with a booster dose at age 16 years (see also the routine childhood vaccination schedule). Either of these vaccines is also recommended for adults who are at increased risk.
MenB is recommended for people ≥ 10 years who are at increased risk of serogroup B meningococcal disease.
Key Points
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Over 90% of meningococcal infections involve meningitis or meningococcemia.
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An asymptomatic nasopharyngeal carrier state is common; transmission usually occurs via direct contact with respiratory secretions from a carrier.
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In the US, most cases are sporadic, typically in children < 2 years of age, but outbreaks can occur, primarily in semiclosed communities (eg, military recruit camps, dormitories, day care centers) and often involve patients aged 5 to 19 years.
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Treat with ceftriaxone or penicillin; add dexamethasone for patients with meningitis.
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Give close contacts a prophylactic antibiotic.
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Vaccinate all children starting at age 11 or 12 years, and selectively vaccinate high-risk younger children and other high-risk people.
More Information
The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
See the following government sites for comprehensive, updated vaccination information:
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Centers for Disease Control and Prevention: Vaccine schedule for children 18 years of age or younger
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Centers for Disease Control and Prevention: Vaccine schedule for adults
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Centers for Disease Control and Prevention: Meningococcal vaccination recommendations for infants
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Advisory Committee on Immunization Practices: Meningococcal vaccine recommendations
