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Growth of Neisseria meningitidis on a selective medium for pathogenic neisseriae. Some strains form pearl-like colonies on the surface of this media. Cultivation 24 hours in an aerobic atmosphere enriched with 5% carbon dioxide, 37 °C.
Neisseria meningitidis exists as normal flora in the nasopharynx of up to 5-15% of adults. It causes the only form of bacterial meningitis known to occur epidemically.
Meningococci only infect humans and have never been isolated from animals because the bacterium cannot get iron other than from human sources (transferrin and lactoferrin).
N. meningitidis is a major cause of morbidity and mortality during childhood in industrialized countries and is responsible for epidemics in Africa and in Asia.
Approximately 2500 to 3500 cases of N. meningitidis infection occur annually in the United States, with a case rate of about 1 in 100,000. Children younger than 5 years are at greatest risk, followed by teenagers of high school age.
Rates in sub-Saharan Africa can be as high as 1 in 1000 to 1 in 100.
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