Meningococcal disease
Meningococcal disease is a serious, vaccine-preventable infection caused by Neisseria meningitidis, also known as meningococcus, a gram negative diplococcus. Meningococcal disease includes meningitis, meningococcal septicemia, or a combination of both, which can be life-threatening and rapidly progressive. If left untreated, the disease has a high mortality rate. Meningitis and meningococcal sepsis are major causes of illness, death, and disability in both developed and under-developed countries.
Meningococcal disease can be transmitted to others through saliva, close contact with an infected individual by inhaling respiratory air droplets. Initial symptoms may be subtle and similar to other bacterial infection, but can quickly progress to include fever, rash, body aches, photophobia and other complications. Neisseria meningitidis colonizes a substantial proportion of the general population without issues, but it can invade the bloodstream, affecting the entire body, most notably limbs and brain, causing serious illness in a small percentage of individuals.
The global incidence of meningococcal disease is relatively low, ranging from 0.0 to 10.2 per 100,000; however, cases in the United States are rising. Serotypes of the bacteria range from various countries, with serotype B accounting for most new cases worldwide. Meningococcal vaccines have sharply reduced the incidence of the disease in developed countries.
Vaccine has also shown to lessen cases of illness and their associated complications as well as death. Current vaccinations cover most of the bacterial strains that causes meningococcal disease. This has led to a decrease of incidence and burden from the disease. Treatment include supportive care, early administration of antibiotics and management of complications associated with infection. Ongoing research continues in an effort to understand specific aspects of meningococcal biology and host interactions; however, the development of improved treatments and effective vaccines is expected to depend on novel efforts by workers in many different fields.
Pathogenesis
Meningococcal disease causes life-threatening meningitis and sepsis conditions. In the case of meningitis, bacteria attack the lining between the brain and skull called the meninges. Infected fluid from the meninges then passes into the spinal cord, causing symptoms including stiff neck, fever and rashes. The meninges begin to swell, which affects the central nervous system.Even with antibiotics, approximately 1 in 10 people who suffer from meningococcal meningitis will die; however, a similar proportion of survivors are affected by limb loss, hearing impairment, or permanent brain damage. The sepsis type of infection is much more deadly, and results in a severe blood poisoning called meningococcal sepsis that affects the entire body. In this case, bacterial toxins rupture blood vessels and can rapidly shut down vital organs. Within hours, patient's health can change from seemingly good to mortally ill.
The N. meningitidis bacterium is surrounded by a slimy outer coat that contains disease-causing endotoxin. While many bacteria produce endotoxin, the levels produced by meningococcal bacteria are 100 to 1,000 times greater than normal. As the bacteria multiply and move through the bloodstream, it sheds concentrated amounts of toxin. The endotoxin directly affects the heart, reducing its ability to circulate blood, and also causes pressure on blood vessels throughout the body. As some blood vessels start to hemorrhage, major organs like the lungs and kidneys are damaged.
Patients with meningococcal disease are treated with a large dose of antibiotic. The systemic antibiotic flowing through the bloodstream rapidly kills the bacteria but, as the bacteria are killed, even more toxin is released. It takes up to several days for the toxin to be neutralized from the body by using continuous liquid treatment and antibiotic therapy.
Classification
Meningococcemia
Meningococcemia, also known as meningococcal septicemia, is an infection of the bloodstream. Meningococcemia makes up about approximately 20% of meningococcal disease cases. Symptoms of meningoccemia may include fever, low blood pressure as well as organ failure. Like many other gram-negative blood infections it can cause disseminated intravascular coagulation, which is the inappropriate clotting of blood within the vessels. DIC can cause ischemic tissue damage when upstream thrombi obstruct blood flow and hemorrhage because clotting factors are exhausted. Small bleeds into the skin cause the characteristic petechial rash, which appears with a star-like shape and mostly appears on the extremity of the body. This is due to the release of toxins into the blood that break down the walls of blood vessels. A rash can develop under the skin due to blood leakage that may leave red or brownish pinprick spots, which can develop into purple bruising. Meningococcal rash can usually be confirmed by a glass test in which the rash does not fade away under pressure.Meningoccemia can also lead to Waterhouse–Friderichsen syndrome, which is associated with disseminated intravascular coagulation or thrombosis of multiple organs and extremities and necrosis of adrenal glands.
Meningitis
Meningococcal meningitis is a form of bacterial meningitis caused by the Neisseria meningitidis bacteria. Meningitis is a disease caused by inflammation and irritation of the meninges, the membranes surrounding the brain and spinal cord. In meningococcal meningitis this is caused by the bacteria invading the cerebrospinal fluid and circulating through the central nervous system. The classic presentation of meningitis includes fever, neck stiffness, and altered mental status; however these symptoms are typically present in less than 50% of cases. Symptoms also differentiate between age groups, with older individuals presenting with altered mental status and localized neurological impairments and younger children showing general symptoms such as irritability, lethargy, or inability to feed.Atypical types of meningococcal disease
N. meningitidis can also result in atypical presentations throughout the body. Atypical types of meningococcal disease include septic arthritis, meningococcal pneumonia, pericarditis and acute gastrointestinal or GI symptoms.GI symptoms from meningococcal disease includes nausea, vomiting and abdominal pain. These symptoms are rare but can occur during the initial phases of infection. These symptoms can often be misdiagnosed as gastroenteritis, also known as a inflammation of the stomach and intestines.
Septic arthritic is also associated with meningococcal disease. Septic arthritis caused by Neisseria meningitidis can appear as joint pain, redness, warmth, and limited movement. It typically affects just one joint—most often the knee—and is more common in very young or older individuals.
Meningococcal pneumonia can appear during influenza pandemics and in military camps. This is a multi-lobar, rapidly evolving pneumonia, sometimes associated with septic shock. With prompt treatment, the prognosis is excellent. Meningococcal pneumonia typical occurs in older individuals and found to be associated with serotype W of N. meningitidis. Although rare, meningococcal pericarditis can occur.
Signs and symptoms
Meningitis
The patient with meningococcal meningitis typically presents with high fever, nuchal rigidity, Kernig's sign, severe headache, vomiting, purpura, photophobia, and sometimes chills, altered mental status, or seizures. Diarrhea or respiratory symptoms are less common. Petechiae are often also present, but do not always occur; their absence does not negate a diagnosis of meningococcal disease. Anyone with symptoms of meningococcal meningitis should receive intravenous antibiotics prior to the results of lumbar puncture being known, as delay in treatment can greatly worsen the prognosis.Meningococcemia
Symptoms of meningococcemia are, at least initially, similar to those of influenza. Typically, the first symptoms include fever, nausea, myalgia, headache, arthralgia, chills, diarrhea, stiff neck, and malaise. Later symptoms include septic shock, purpura, hypotension, cyanosis, petechiae, seizures, anxiety, and multiple organ dysfunction syndrome. Acute respiratory distress syndrome and altered mental status may also occur. The petechial rash appear with the 'star-like' shape. Meningococcal sepsis has a greater mortality rate than meningococcal meningitis, but the risk of neurologic sequelae is much lower.Diagnosis
Diagnosing meningococcal disease is vital; death can occur in a person within 6-12 hours with initial signs and symptoms.Diagnosis includes clinical evaluation based on symptoms blood cultures, cerebrospinal fluid analysis, basic metabolic panel, and possibly imaging.
Lumbar puncture is the gold standard for identifying a person has meningitis and rule out other causes of infection. This fluid covers the brain and spinal cord. This test should be completed unless a person has increased pressure in the brain such as swelling in the optic nerve or altered mental status.
Computer tomography can be used if diagnosis is unclear and if a person has depressed mental status.
Prevention
The most effective method of prevention is a vaccine against N. meningitidis. Different countries have different strains of the bacteria and therefore use different vaccines. Twelve serogroups exist, with six having the potential to cause a major epidemic - A, B, C, X, Y and W135 are responsible for virtually all cases of the disease in humans. Vaccines are currently available against all six strains, including a newer vaccine against serogroup B. The first vaccine to prevent meningococcal serogroup B disease was approved by the European Commission on 22 January 2013.Vaccines offer significant protection from three to five years to more than eight years.