Neisseria meningitidis

Neisseria meningitidis

Description, Causes and Risk Factors:

Abbreviation: N. meningitidis

A bacterial species found in the nasopharynx of humans but not in other animals; the causative agent of meningococcal meningitis and meningicoccemia; virulent organisms are strongly Gram negative and occur singly or in pairs; in the latter case the cocci are elongated and are arranged with long axes parallel and facing sides kidney shaped; groups characterized by serologically specific capsular polysaccharides are designated by capital letters (the main serogroups being A, B, C, and D).

Neisseria Meningitidis is a bacteria that is best known for its role in endemic bacterial meningitis. N. Meningitidis is described as a gram-negative diplococci. The fact that this bacteria is gram negative means that there is very little or no peptidoglycan in the cell wall. The word diplococci is describing the appearance of N. Meningitidis. This means that two of the spherically shaped bacteria push up against each other. The side where they meet up becomes flat so each individual will look slightly oblong. The picture to the right shows the shape of the bacteria.

Neisseria Meningitidis is non motile and is transferred among people via direct contact with bodily fluids in which the bacteria has inhabited. This bacteria has also been found to be oxidase positive which means it contains the enzyme cytochrome c oxidase and is capable of using oxygen for energy via an electron transfer chain. Since N. Meningitidis is oxidase positive it means it is aerobic.

The fact that N. Meningitidis is known for its role in bacterial meningitis it is known as a pathogen. This bacteria lives in the mucous membranes of humans as a parasite. It has been responsible for many epidemics across the world and there have been many deaths associated with these epidemics.

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.


In persons over age 2, common symptoms are high fever, headache, and stiff neck. These symptoms can develop over several hours, or they may take 1 to 2 days. Other symptoms can include nausea, vomiting, sensitivity to light, confusion, and sleepiness. In advanced disease, bruises develop under the skin and spread quickly.

In newborns and infants, the typical symptoms of fever, headache, and neck stiffness may be hard to detect. Other signs in babies might be inactivity, irritability, vomiting, and poor feeding.

As the disease progresses, patients of any age can have seizures.


The gold standard of diagnosis is isolation of N. meningitidis from sterile body fluid.A cerebrospinal fluid (CSF) specimen is sent to the laboratory immediately for identification of the organism. Diagnosis relies on culturing the organism on a chocolate agar plate. Further testing to differentiate the species includes testing for oxidase, catalase (all clinically relevant Neisseria show a positive reaction) and the carbohydrates maltose, sucrose, and glucose test in which N. meningitidis will ferment (that is, utilize) the glucose and maltose. Serology determines the subgroup of the organism.

If the bacteria reach the circulation, then blood cultures should be drawn and processed accordingly.

Clinical tests that are used currently for the diagnosis of meningococcal disease take between 2 and 48 hours and often rely on the culturing of bacteria from either blood or cerebrospinal fluid (CSF) samples. However, polymerase chain reaction (PCR) tests can be used to identify the organism even after antibiotics have begun to reduce the infection. As the disease has a fatality risk approaching 15% within 12 hours of infection, it is crucial to initiate testing as quickly as possible but not to wait for the results before initiating antibiotic therapy.


Early diagnosis and treatment are very important. If symptoms occur, the patient should see a doctor right away. Antibiotics used for N. meningitidis infection include: Penicillin G, ampicillin, chloramphenicol, ceftriaxone, and Oily Chloramphenicol. This organism has shown resistance to sulfonamides and rifampin.

Persons with confirmed N. meningitidis infection should be hospitalized immediately for treatment with antibiotics. Third-generation cephalosporin antibiotics (i.e. cefotaxime, ceftriaxone) should be used to treat a suspected or culture-proven meningococcal infection before antibiotic susceptibility results are available. Empirical treatment should also be considered if a lumbar puncture, to collect cerebrospinal fluid (CSF) for laboratory testing, cannot be done within 30 minutes of admission to hospital. Antibiotic treatment may affect the results of microbiology tests, but a diagnosis may be made on the basis of blood-cultures and clinical examination.

There are currently three vaccines available in the US to prevent meningococcal disease. All three vaccines are effective against the same serogroups: A, C, Y, and W-135. Two meningococcal conjugate vaccines (MCV4) are licensed for use in the US. The first conjugate vaccine was licensed in 2005, the second in 2010. Conjugate vaccines are the preferred vaccine for people two through 55 years of age. A meningococcal polysaccharide vaccine (MPSV4) has been available since the 1970s and is the only meningococcal vaccine licensed for people older than 55. MPSV4 may be used in people ages 2 - 55 years old if the MCV4 vaccines are not available or contraindicated.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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