This is the best known form of the disease. Various microorganisms that can cause this type of infection depend on the patient’s age and other factors as, for example, the immune status of the patient. This system is responsible for protecting the human body from external aggression as they are infections; malfunction involves a greater predisposition to allergies.
Of all the bacteria responsible for meningitis include:
- Streptococcus pneumoniae, or pneumococcus. It is the most common cause of meningitis. This bacterium colonizes the pharynx often people without giving any disease. It can be found in 5-10% of healthy adults and 20-40% of healthy children. However, occasionally, the immune system can not control their growth and reach the meninges through the blood, or directly by contiguity in case there is an infection of the sinuses (sinusitis) or middle ear (otitis average), or skull fracture after trauma. Pneumococcus can also be the cause of pneumonia (pneumonia) that occasionally can be associated with meningitis. Pneumococcal meningitis can occur at any age. It is more common to occur in people with certain immune deficiencies (eg treatment with immunosuppressive drugs, or people with disorders of the spleen), also in diabetics, alcoholics, people with kidney or liver failure, undernourished, or after trauma in which cranial fractures occur. Their mortality is very high. A vaccine that covers some pneumococcal serotypes and has lowered the incidence of pneumococcal meningitis in children.
- The Neisseria meningitidis or meningococcus, which is responsible for many outbreaks of meningitis, especially in children and youth. The meningococcus can colonize the pharynx of many people without giving disease. Meningitis can occur in people with a disorder of the immune system, but often also occurs in healthy people. There is an effective vaccine against meningococcus, but unfortunately does not cover all serotypes of this bacteria there.
- In newborns and elderly disease-causing, bacteria can be totally different from the rest of the population. For example, newborns can give meningitis bacteria called Streptococcus agalactiae (also called group B strep). This is a bacterium that colonizes the female genital tract and infect the newborn during delivery. Fortunately, study and eradication of bacteria in pregnant women has decreased the incidence of this complication. In children under five was prevalent meningococcal bacteria found in the respiratory tract called Haemophilus influenzae type b. The childhood immunization has greatly diminished this disease. Children, the elderly, pregnant women, and some immunocompromised persons may suffer meningitis bacteria called Listeria monocytogenes. It is often associated with the consumption of dairy products or some raw vegetables and has a poor prognosis.