Bacterial meningitis: symptoms, causes, treatment, prognosis

What is bacterial meningitis?

Bacterial meningitis is a disease of the central nervous system caused by certain types of bacteria. Meningitis characterized by inflammation of the membranes around the brain or spinal cord. The inflammation can start suddenly (acute) or develop gradually (sub-acute). Major symptoms and signs may include fever, headache, and a stiff neck, sometimes with muscle pain. Patients may also experience nausea, vomiting, and other symptoms.

Signs and symptoms

Bacterial meningitis in adults and children is often preceded by respiratory illness or sore throat. Most forms of bacterial meningitis are acute. In its acute form, the disorder is characterized by sudden fever, headache, neck stiffness and vomiting. Adults can become seriously ill within 24 hours. In children, the course of the infection may be even shorter.

Symptoms in older children and adults can progress from irritability to confusion, drowsiness, and stupor, which can lead to coma. Distributed 

dehydration of the body. Other symptoms may include:

• chills;
• excessive sweating;
• weakness;
• loss of appetite;
• inability to tolerate bright light (photophobia).

Later symptoms may include hydrocephalus (dropsy of the brain [accumulation of fluid in the brain cavity]), paralysis on one side of the body (hemiparesis), hearing loss, or other neurological disorder.

Among children aged 3 months to 2 years fever, refusal to feed, vomiting, irritability, and epilepsy. A piercing cry and a raised or hard soft spot (fontanelle) on the top of the head (where parts of the bones that have not yet hardened meet). As the incidence of meningitis is the highest in this age group, any unexplained fever should be investigated. After a few days, cerebral fluid can build up inside the tough outer membrane that covers the brain (subdural effusion). Typical signs of meningitis include seizures, persistent fever, and an increase in head size. You may also experience brain abscess or accumulation of subdural pus.

Neonatal bacterial meningitis in newborns up to 4 weeks old can be caused by infections in parts of the body other than the brain or spine. Some cases may arise due to complications arising at birth. The disorder is characterized by subtle and nonspecific features such as tremors, intermittent breathing (apnea), vomit, diarrhea and yellowish skin color (jaundice). Signs of infection in other parts of the body are usually also present (for example, otitis media of the middle ear).

Bacterial meningitis caused by group B pneumococcal bacteria may be present in the first 10 days of life when it often accompanies lung disease. Usually, however, this form of meningitis occurs after 10 days of age as an isolated disease.

Causes

Bacterial meningitis is the most common type of meningitis. Three types of bacteria are responsible for 80% of all bacterial meningitis.

• Hemophilus influenzae type B (Haemophilus influenzae type B),
• Streptococcus pneumoniae (Pneumococcal infection/Пневмококк)
• Neisseria meningitidis (Meningococcal infection/Менингококк).

All three types are most common in winter.

Gram-negative bacteria such as Escherichia coli (E. coli), Klebsiella (Klebsiella), or Pseudomonas (Pseudomonas) often cause bacterial meningitis in newborns. Other types of bacteria that can cause the disorder are streptococci, staphylococci (Staphylococcus aureus) or Listeria monocytogenes, which causes listeriosis.

Bacterial meningitis, caused by Haemophilus influenzae type B bacteria, is most common in children over 1 month old and young children. It usually does not occur in adults, except in connection with another condition, such as a head injury or impaired immunity. Bacterial meningitis caused by pneumococcus is most common in adults, especially with alcoholism, chronic otitis media (ear infection), sinusitis (inflammation of the lining of the sinuses), mastoiditis (infection of the bone behind the ear), closed head injury, recurrent meningitis, pneumococcal pneumonia, or sickle cell disease anemia.

Bacterial meningitis from gram-negative organisms such as Escherichia coli and Klebsiella-Enterobacter is called gram-negative meningitis and often occurs after injury or surgery on the central nervous system, or as a result blood poisoning. Newborns or immunocompromised people can also become infected.

Staphylococcal meningitis, another form of bacterial meningitis, occurs after blood poisoning (for example, due to endocarditiswhich is inflammation of the inner lining of the heart), open head injury, or neurosurgery.

Listeria meningitis is another form of meningitis that occurs in newborns, in patients with chronic renal failure or in adults taking immunosuppressants (eg, organ transplant patients).

Intravenous injection of drugs through unsterilized needles can cause blood poisoning, which can lead to bacterial meningitis.

Of all the bacteria that cause bacterial meningitis, Hemophilus influenza type B is the most common and represents nearly half of all cases of bacterial meningitis. Meningococcal meningitis is about 27 percent and pneumococcal meningitis is about 11 percent.

It is believed that the bacteria that cause bacterial meningitis are carried by about ten percent of the population in their throats. It is unclear why only a very small percentage of people develop this disease.

Affected populations

About 2,600 sporadic cases of bacterial meningitis are reported each year in the United States alone. Meningitis due to pneumococcal infections affects approximately 1.1 people in 100,000. Haemophilus influenzae meningitis affects approximately 0.2 in 100,000 people. About 70 percent of all bacterial meningitis occurs in children under 5 years of age. Children under 2 years of age are at greatest risk of infection, and men are more likely to be affected than women. Bacterial meningitis in general most often occurs during the first month of a newborn's life and usually caused by gram-negative bacteria such as Escherichia coli or group streptococci B. Bacterial meningitis due to Hemophilus influenzae type B is most common in children over 1 month old and young children. Bacterial meningitis, caused by pneumococcal bacteria, is most common in adults, but an estimated 1,400 cases of pneumococcal disease occur annually in children under five years of age. meningitis.

Symptomatic disorders

Symptoms of the following disorders may mimic those of bacterial meningitis. Comparisons can be useful for differential diagnosis:

• Meningitischaracterized by inflammation of the membranes around the brain or spinal cord. This inflammation can be caused by various types of bacteria, viruses, fungi, cancers, or chemical reactions to certain injections into the spinal canal.
• Encephalitis - a brain infection. There are different types of this disorder which are caused by different types of viruses. Encephalitis can also be caused by hypersensitivity caused by a virus or other protein that is foreign to the body. Symptoms may include headache, drowsiness, hyperactivity, and / or general weakness. This disorder may have some symptoms that are similar to those of all meningitis, such as stiffness occipital muscles, altered reflexes, confusion, speech disorders, possible seizures, paralysis and coma.
• Primary amoebic meningoencephalitis (PAM) - brain infection. PAM is characterized by severe headache, high fever, nausea, vomiting, a stiff neck, and, in some cases, hallucinations. Some sufferers may experience seizures, coma and other life-threatening complications. SAM occurs in people who have inhaled water from lakes, ponds, rivers, or streams contaminated with the microorganism Naegleria fowleri amoebae. Infection most often occurs in warm areas during the summer months. AMP cases have been reported primarily in the southern and central United States, Russia, southern Australia, New Zealand, Europe, Africa, and Central America. A diagnosis of AMP can be suspected on the basis of careful clinical evaluation and the patient's detailed history.

Diagnostics

If a child under 2 years of age has a fever and the parents notice that the child has become inexplicably irritable, or drowsy, contact a doctor immediately, especially if symptoms persist after an appropriate dose acetaminophen.

Children need immediate medical attention, most often in the emergency room, if they have any of the following symptoms:

• the child is extremely irritable or unusually sleepy;
• body temperature is lowered;
• he refuses to eat;
• convulsions appear;
• stiff neck.

Emergency medical care is needed for adults if:

• the appearance of headache and stiff neck muscles, especially at high temperatures;
• confusion and decreased concentration;
• lethargy or apathy;
• convulsive seizures;
• rash with fever or a stiff neck

During the physical examination, your doctor checks for typical signs of meningitis, especially a stiff neck. He will also check for rashes, especially in children, adolescents, and young adults, and other symptoms that may indicate a cause. The doctor may suspect bacterial meningitis based on symptoms and test results, but to confirm the diagnosis, it is necessary to carry out tests and establish the presence of specific bacteria that caused disease.

As soon as doctors suspect bacterial meningitis, the first thing they do is take a blood sample for culture (cultivation) in the laboratory and analysis. Then, treatment with antibiotics and corticosteroids is immediately prescribed, without waiting for the test results, due to the rapid progression of the disease.

- Surveys.

After starting treatment, doctors quickly do a lumbar puncture (lumbar puncture), if safe, to confirm the diagnosis.

However, if there is a suspicion of increased intracranial pressure (for example, due to an abscess, tumor, or other mass in the head brain), then first you need to perform computed tomography (CT) or magnetic resonance imaging (MRI) to exclude the presence of volumetric education. Prescribing a lumbar puncture with increased intracranial pressure can be dangerous. Parts of the brain can move downward. If these parts are forced through small holes in the tissues that divide the brain into sections, a life-threatening pathology called a hernia of the brain occurs. After a decrease in intracranial pressure or if the absence of a mass is detected, a lumbar puncture is performed and doctors adjust treatment, if necessary, after receiving results.

In a lumbar puncture, a thin needle is inserted between two bones (vertebrae) in the lower spine to collect cerebrospinal fluid.

Then the following actions are performed:

• The cerebrospinal fluid is carefully examined: it should be clear, but in patients with meningitis, the fluid becomes cloudy.
• The pressure in the subarachnoid space (containing the cerebrospinal fluid) is measured during the collection of the cerebrospinal fluid: usually with meningitis, the pressure is high.
• An analysis of cerebrospinal fluid is carried out in a laboratory: the level of sugar and protein is measured, as well as the number and type of leukocytes in the fluid. This information helps the doctor diagnose meningitis and distinguish between the bacterial or viral form of the disease.
• Cerebrospinal fluid is examined under a microscope to check for the presence and identification of bacteria. A special stain (called Gram stain) is used to show bacteria more clearly and to better identify them.
• Other examinations.

For quick identification of certain bacteria, for example, meningococcus and pneumococcus, other assays may be used. Some of these tests identify specific bacteria by recognizing specific proteins (antigens) on the surface of such bacteria. The method can be used to identify the unique DNA sequence of a bacterium polymerase chain reaction (PCR), which creates a large number of copies of the gene. Some tests can quickly analyze large sections of genetic material. These tests can identify organisms in the cerebrospinal fluid that cannot be detected by other methods. However, such analyzes are not always available.

Cerebrospinal fluid culture (to grow bacteria) is also done. Culture helps the doctor determine the presence of bacteria and, if positive, identify the type of bacteria and antibiotics that may be most effective against them. Sowing usually takes 24 hours or more. If culture or other tests identify bacteria in the cerebrospinal fluid, the diagnosis of bacterial meningitis is confirmed.

Before a diagnosis of meningitis is confirmed, cerebrospinal fluid or blood may be used to check for viruses, fungi, cancer cells and other substances that may not be detected in standard tests. It is especially important to be tested for the herpes simplex virus, which can infect the brain (causing encephalitis).

The doctor also tests blood, urine, and mucus from the nose or throat. If the patient has a rash, using a small needle, the doctor takes a sample of fluid and tissue from the areas of the skin under the rash. These samples are cultured and examined under a microscope for the presence of bacteria.

Standard treatments

Because acute bacterial meningitis can cause permanent brain damage, nerve damage, or death within hours, treatment should be started as soon as possible, without waiting for the results of diagnostic tests and, most often, even before performing a spinal cord puncture.

At this stage, the doctor probably does not know about the specific bacteria that caused the disease, and therefore does not know which antibiotics will be most effective. Therefore, he chooses the antibiotic that is most effective against the bacteria most likely to cause the infection. The doctor will usually use two or more antibiotics that are effective against many bacteria. The antibiotic is given intravenously. Because inflammation of the brain (encephalitis) from the herpes virus can be similar to bacterial meningitis, antiviral drugs are often prescribed to work against the virus. Immediately after identification of the infectious microorganism, as a rule, a specific type of bacteria, antibiotics are replaced with other, more effective ones. The use of unnecessary antibiotics and antiviral drugs is being phased out.

Dexamethasone (a corticosteroid) is used to reduce edema brain. It is given 15 minutes before or at the same time as the first dose of the antibiotic, as the swelling can worsen due to the breakdown of bacteria by the antibiotic. The use of dexamethasone continues for 4 days. Dexamethasone can also reduce intracranial pressure. In case of damage adrenal glands (as occurs with Waterhouse-Friederiksen syndrome) dexamethasone and others toorticosteroids can replace corticosteroids, which are produced by the adrenal glands.

Other infections that may or have been caused by meningitis also require treatment. Such infections include sepsis, pneumonia and a heart infection (bacterial endocarditis).

Fluid that is lost due to fever, sweating, vomiting, and poor appetite must be replenished, usually intravenously.

Most often, people with bacterial meningitis end up in the intensive care unit, as this disease affects many organs and causes serious complications.

- Treatment of complications.

Complications may require special treatment.

• Convulsions: Anticonvulsants are prescribed.
• Shock: to increase blood pressure and treat shockAs with Waterhouse-Friederiksen syndrome, additional fluids and some drugs (intravenously) are given.
• Coma: artificial ventilation of the lungs may be necessary.
• Dangerously high pressure inside the skull (intracranial hypertension): the head of the bed is raised and corticosteroids are used to reduce intracranial pressure. If the pressure needs to be reduced quickly, artificial ventilation is used. Artificial ventilation reduces the amount of carbon dioxide in the blood and thus quickly but briefly reduces the pressure in the cerebrospinal fluid. Mannitol can also be given intravenously. Mannitol removes fluid from the brain into the bloodstream and thus reduces intracranial pressure. Intracranial pressure is monitored using a small tube (catheter) connected to a measuring device. The catheter is inserted through a small hole drilled into the skull. The catheter can also be used to pump out cerebrospinal fluid, thus relieving pressure as needed.
• Subdural empyema: for a successful recovery, it may be necessary to drain the accumulated pus.

Forecast

When treatment is started early, most people with meningitis recover successfully. If treatment is delayed, the likelihood of permanent damage to the brain, nerves, and even death increases, especially in young children or people over 60.

For some people, seizures caused by meningitis require life-long treatment.

A person with meningitis may have problems such as a permanent decrease in mental performance, memory problems, and concentration, learning disabilities, behavioral problems, paralysis, double vision, and partial or complete loss hearing.

Prophylaxis

People with bacterial meningitis (especially meningococcal meningitis) are usually isolated until the infection is brought under control and infect others, usually within 24 hours.

For several forms of bacterial meningitis are available vaccines.

- Meningococcal meningitis.

One of the vaccines (meningococcal vaccine) helps prevent meningococcal meningitis. It is administered to the following people:

• children aged 2 months to 10 years if their immune system is weakened (for example, if they have an immunodeficiency state) or if they do not have a functioning spleen;
• all children aged 11 to 12 and a booster dose at age 16;
• older children and students living in dormitories, if they have not already been vaccinated;
• recruits if they have not yet been vaccinated;
• people traveling to countries or living in countries where this infection is common;
• people who may have constant contact with bacteria, such as laboratory technicians.

The vaccine is also used in the event of an epidemic outbreak or threat of an epidemic among a group of people living together in a limited area (for example, in a military barracks).

- Meningitis caused by pneumococcus.

The vaccine that protects against this infection (pneumococcal vaccine) is part of the childhood vaccination program.

- Meningitis caused by Haemophilus influenzae.

Children are now routinely immunized with Haemophilus influenzae type b vaccine. In developed countries, this vaccine has virtually eliminated the previously common cause of meningitis in children.

- Prevention after exposure to meningitis.

Family members, medical staff and others who are in close contact with patients with meningococcal meningitis, have to take an antibiotic (such as rifampin or oral ciprofloxacin or ceftriaxone by injection) for prevention. Prophylactic antibiotics are usually only needed for meningococcal meningitis and meningitis caused by Haemophilus influenzae.