Neisseria meningitidis is a bacterium that commonly resides in the human upper respiratory tract. This microorganism can live in the nose and throat of individuals without causing any illness, a state known as asymptomatic carriage. While many people carry it harmlessly, the bacterium has the potential to invade the body and cause severe, life-threatening infections.
Meningococcal Disease Manifestations
When Neisseria meningitidis causes illness, it manifests in two main forms. Meningococcal meningitis involves an infection of the meninges, the protective membranes surrounding the brain and spinal cord. Individuals often experience a sudden onset of symptoms, including fever, headache, and a stiff neck. Other signs include nausea, vomiting, increased sensitivity to light (photophobia), and changes in mental state, such as confusion or drowsiness.
Meningococcemia is a bloodstream infection. Symptoms include fatigue, cold hands and feet, and severe aches in muscles, joints, or the abdomen. Rapid breathing, diarrhea, and vomiting may also occur. A distinguishing feature is a dark purple rash (petechiae or purpura) resulting from bleeding under the skin. The rash can start as small, pinprick-like spots and quickly enlarge to resemble bruises, signaling a medical emergency.
Transmission and High-Risk Populations
The Neisseria meningitidis spreads from person to person through respiratory and throat secretions, such as saliva or spit. Transmission occurs during close or lengthy contact with an infected individual. Examples include kissing, sharing eating utensils or drinking glasses, or being exposed to coughs and sneezes. The bacteria are not as easily spread as common cold or flu viruses, requiring more intimate interaction.
Certain populations have a higher likelihood of contracting meningococcal disease, including:
- Infants younger than one year old.
- Adolescents and young adults, particularly those aged 16 through 23 years.
- Individuals living in crowded environments, such as college dormitories or military barracks.
- People with specific medical conditions, including spleen damage or removal, or certain immune system deficiencies like complement component deficiencies.
Prevention Through Vaccination
Vaccination offers the most effective strategy to prevent meningococcal disease. Several types of vaccines are available, targeting different strains of the bacteria, known as serogroups. There are at least 12 identified serogroups of N. meningitidis, but serogroups A, B, C, W, and Y are most frequently associated with disease.
Two main types of meningococcal vaccines are used in the United States to protect against these serogroups. MenACWY vaccines provide protection against serogroups A, C, W, and Y. These vaccines are routinely recommended for preteens at 11 or 12 years of age, with a booster dose advised at age 16 to maintain protection.
Separate MenB vaccines are available to protect against serogroup B. These are recommended for adolescents and young adults aged 16 through 23 years based on individual clinical decision-making. MenB vaccines are also recommended for individuals aged 10 years or older who are at increased risk for serogroup B meningococcal disease, such as during outbreaks or for those with certain underlying medical conditions.
Diagnosis and Medical Interventions
When meningococcal disease is suspected, it requires immediate medical attention and hospitalization due to its rapid progression. Healthcare providers diagnose the infection through a combination of medical history, physical examination, and specific laboratory tests.
Key diagnostic tests include blood cultures to grow the bacteria from a blood sample. A spinal tap (lumbar puncture) is often performed to collect and analyze cerebrospinal fluid (CSF) for the presence of Neisseria meningitidis. Polymerase chain reaction (PCR) tests can also detect bacterial genetic material in blood or CSF, and Gram stains may reveal the bacteria under a microscope.
Treatment involves the prompt administration of antibiotics, often initiated even before diagnostic test results confirm the infection, given the swift and severe nature of the disease. Third-generation cephalosporins like ceftriaxone or cefotaxime are commonly used. Patients also receive supportive care in the hospital, which may include intravenous fluids, oxygen therapy, and medications to manage complications such as low blood pressure.