Meningitis, bacterial

Infectious diseases of the central nervous system (CNS) can be caused by viral, bacterial and parasitic pathogens as well as fungi. In the case of bacterial meningitis, a bacterial infection causes inflammation of the membranes of the brain and spinal cord. If the inflammation also involves the brain, it is referred to as meningoencephalitis. Bacterial meningitis can also be purulent under certain circumstances. Bacterial meningitis is still a serious disease, despite optimal treatment, and around 15 to 20 % of pneumococcal meningitis cases are fatal.

Infection of the membranes of the brain and spinal cord (meninges) can occur either through pathogen transmission via the blood or through direct infection from the paranasal sinuses or the ear.

Severe bacterial meningitis often leads to involvement of the brain, resulting in so-called meningoencephalitis.

The most common pathogens causing bacterial meningitis are

• meningococci

• pneumococci

• listeria

• Staphylococci

• Haemophilus influenzae

The leading symptoms of bacterial meningitis are

• Headache (in 83 to 87% of cases)

• Meningismus (in 75 to 83 % of cases)

• Fever (in 77% of cases)

• Vigilance disorder (in around 69% of cases)

Other symptoms that often occur in the course of bacterial meningitis are

• Nausea

• vomiting

• Photophobia (shyness)

• Confusion

• Epileptic seizures

• Skin hemorrhages (petechiae)

• Impaired consciousness up to loss of consciousness

The symptoms develop within a few hours to a few days. The typical symptoms of meningitis are often absent in infants and young children. The symptoms of viral meningitis are also much more variable and meningeal irritation signs are often less pronounced.

Serious complications can occur during the course of bacterial meningitis in particular. Examples of complications include organ infarctions, bleeding, cerebral edema, thrombosis or inflammation-related swelling of the brain parenchyma.

Meningitis is often diagnosed with the help of a detailed medical history, a physical examination, a cerebrospinal fluid puncture, a blood test and various imaging procedures (e.g. computer tomography or magnetic resonance imaging). With the help of computer tomography (CT), for example, complications (e.g. brain abscesses) can be quickly identified and, if necessary, treated.

During a lumbar puncture (cerebrospinal fluid puncture), cerebrospinal fluid is removed from the patient's spinal canal using a cannula. These samples can then be further examined for various pathogens and signs of inflammation.

The blood test for meningitis usually includes a bacterial culture, a complete blood count, signs of inflammation, glucose and possibly other laboratory values. In the case of bacterial meningitis, the blood count often shows an increase in white blood cells (leukocytosis) and an increase in C-reactive protein (CRP). A procalcitonin determination can help to differentiate between bacterial and viral meningitis.

Bacterial meningitis can also lead to hearing and balance disorders, which can be checked using audiometric hearing tests, auditory evoked potentials (brainstem audiometry, AEP) and balance tests.

Common pathogens

The most common pathogens causing bacterial meningitis in adults and children are pneumococci and meningococci. Rarer pathogens are listeria (< 5 %), staphylococci (< 5 %) and pseudomonads or gram-negative enterobacteria. Due to the high vaccination rate of children against H. influenzae, Haemophilus meningitis has become much rarer than in the past.

In newborns, around 70 % of meningitis is caused by group B streptococci. Various mixed infections with different pathogens can occur, particularly in patients with immune deficiencies (e.g. HIV, leukemia, various immunodeficiencies) or after open craniocerebral trauma. Splenectomies lead to an increased risk of meningitis caused by pneumococci, meningococci and H. influenzae.

It is crucial to start broad antibiotic therapy quickly if bacterial meningitis is clinically suspected. Treatment usually takes place in an inpatient setting. Antibiotics and glucocorticoids can thus be administered intravenously and quickly and effectively. The antibiotic should be able to cross the blood-brain barrier well. As soon as the exact meningitis pathogen has been identified via bacterial culture or CSF diagnostics, antibiotic therapy can be switched to targeted antibiotics.

Recommended antibiotic therapies for various pathogens:

The duration of antibiotic treatment varies depending on the pathogen. N. meningitidis (meningococcus) and H. influenzae should be treated with antibiotics for 7 to 10 days. Infections with L. monocytogenes (listeria) and gram-negative enterobacteria often require antibiotic therapy for 14 to 21 days.

According to current guidelines, dexamethasone therapy(glucocorticoid) is particularly recommended for adults with suspected community-acquired meningitis. The mortality rate of pneumococcal meningitis is lower with dexamethasone and hearing impairment in the course of meningitis caused by H. influenzae also occurs less frequently. The dosage is often 4 times 10 mg / day over a period of 4 days. It is started with the first course of antibiotics. This should always be accompanied by gastric protection (e.g. omeprazole) and thrombosis prophylaxis.

Particularly in the case of meningitis caused by pneumococci, a local spread of the pathogen with a new infectious focus (e.g. ear infection, sinusitis) must be considered, which may need to be surgically treated.

Acute bacterial meningitis is life-threatening and can lead to serious complications (e.g. cardiovascular shock). In the most severe cases, bacterial meningitis can lead to death within hours, which is why rapid medical diagnosis and treatment are extremely important.

Pneumococcal and listeria meningitis still have a mortality rate of 10 to 30 %, despite adequate medical treatment. In contrast, the mortality rate for meningitis caused by meningococci is around 3 to 8 %.

Brain abscesses are a serious complication of meningitis caused by the spread of pathogens via the blood or through the migration of pathogens to neighboring structures. In the case of a brain abscess, local, invasive relief is often indicated in addition to antibiotic therapy. Another dreaded complication is Waterhouse-Friderichsen syndrome (consumption coagulopathy, adrenal cortical insufficiency), which is usually fatal.

After surviving meningitis, around 10 to 40 % of those affected suffer from persistent sequelae, such as neurological damage, hearing impairment, concentration and memory disorders, paralysis and epilepsy.

Preventive measures against meningitis include vaccination against the various meningitis pathogens such as:

• Meningococcal vaccination

• pneumococcal vaccination

• Vaccination against Haemophilus influenzae