Meningococcal Infections

Two major meningococcal infections (meningitis and meningococcemia) are caused by the gram-negative bacteria Neisseria meningitidis, which also causes primary pneumonia, purulent conjunctivitis, endocarditis, sinusitis, and genital infection.

Meningococcemia occurs as simple bacteremia, fulminant meningococcemia and, rarely, chronic meningococcemia. It often accompanies meningitis. Meningococcal infections may occur sporadically or in epidemics; virulent infections may be fatal within a matter of hours.

In 2001, about 670 cases of meningococcal disease were reported to Australian health authorities. Every year there are about 35 deaths from meningococcal disease in Australia. Australia has a relatively low rate of meningococcal infection and epidemics are rare.

There are 13 strains of meningococcal disease. The majority of cases seen in Australia are caused by group B (62 per cent of all cases) for which there is presently no vaccine. About 32% of all meningococcal cases in Australia are caused by group C bacteria. While disease caused by group C is less common, it accounts for almost two-thirds of all deaths from meningococcal infection in Australia.

Causes

Meningococcal infections occur most often among children (ages 6 months to 1 year) and men, usually military recruits, because of overcrowding.

N.meningitidis has seven serogroups (A, B, C, D, X, Y, Z); group A causes most epidemics. These bacteria are often present in upper respiratory flora. Transmission takes place through inhalation of an infected droplet from a carrier (an estimated 2% to 38% of the population). The bacteria then localize in the nasopharynx.

Following an incubation period of approximately 3 or 4 days, the bacteria spread through the bloodstream to the joints, skin, adrenal glands, lungs, and central nervous system. The tissue damage that results (possibly due to the effects of bacterial endotoxins) produces symptoms and, in fulminant meningococcemia and meningococcal bacteremia, progresses to hemorrhage, thrombosis, and necrosis.

Signs and symptoms

People can carry the bacteria without becoming ill, but can pass it to others who do become ill. The first signs of meningococcal infection are much like the flu. Symptoms include fever, headache, nausea, vomiting, and feeling unwell. These symptoms are usually worse than those for the flu, and progress quickly to a bad headache, stiff neck, and/or a reddish-purple, tiny, bruise-like skin rash.

In young children, the most obvious symptom may be a major change in behaviour, such as sleepiness, irritability or excessive crying.

Diagnosis

Isolation of N meningitidis through a positive blood culture, cerebrospinal fluid (CSF) culture, or lesion scraping confirms the diagnosis except in nasopharyngeal infections, because N meningitidis exists as part of the normal nasopharyngeal flora.

Tests that support the diagnosis include counterimmunoelectrophoresis of the CSF or blood, a low white blood cell count and, in patients with skin or adrenal hemorrhages, decreased platelet and clotting levels. Diagnostic evaluation must rule out Rocky Mountain spotted fever and vascular purpuras.

Treatment

As soon as meningococcal infection is suspected, treatment begins with large doses of aqueous penicillin G, ampicillin, or a cephalosporin, such as cefoxitin and moxalactam; or, for the patient who's allergic to penicillin, chloramphenicol I.V. Therapy may also include mannitol for cerebral edema, heparin I.V. for DIC, dopamine for shock, and digoxin and a diuretic if heart failure develops.

Supportive measures include fluid and electrolyte maintenance, proper ventilation (patent airway and oxygen if necessary), insertion of an arterial or central venous pressure (CVP) line to monitor cardiovascular status, and bed rest.

Chemoprophylaxis with rifampin or minocycline is useful for facility workers who come in close contact with the patient; minocycline can also temporarily eradicate the infection in carriers.

Is meningococcal disease the same as meningitis?

Prevention

Practice good personal hygiene, including frequent hand washing and do not share any item that may have saliva or spit on it to prevent meningococcal infection.

If you have been in close, direct contact with a person with meningococcal infection, an antibiotic and a vaccination are recommended and provided free. This helps to prevent the development of the disease. Although these measures are very effective, it is important that a doctor be consulted if symptoms of the disease develop.