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Bacterial meningitis

Overview

A bacterial infection which results in inflammation of the meninges of the brain. The meninges are the membranes that cover the brain and spinal cord. Serious cases can result in brain damage or even death. The condition most commonly affects young children.

Symptoms - Bacterial meningitis

  • Tachypnea 
  • Fever
  • Tachycardia 
  • Hypoxemia 
  • Diaphoresis 
  • Hypothermia
  • Rigors
  • Weakness 
  • Photophobia 
  • Seizures 
  • Fever 
  • Headache 
  • Stiff neck 
  • Aching muscles 
  • Nausea 
  • Vomiting

Causes - Bacterial meningitis

Bacteria that enter the bloodstream and travel to the brain and spinal cord cause acute bacterial meningitis. But it can also occur when bacteria directly invade the meninges. This may be caused by an ear or sinus infection, a skull fracture, or, rarely, after some surgeries.

Several strains of bacteria can cause acute bacterial meningitis, most commonly:

  • Streptococcus pneumoniae (pneumococcus). This bacterium is the most common cause of bacterial meningitis in infants, young children and adults in the United States. It more commonly causes pneumonia or ear or sinus infections. A vaccine can help prevent this infection.
  • Neisseria meningitidis (meningococcus). This bacterium is another leading cause of bacterial meningitis. These bacteria commonly cause an upper respiratory infection but can cause meningococcal meningitis when they enter the bloodstream. This is a highly contagious infection that affects mainly teenagers and young adults. It may cause local epidemics in college dormitories, boarding schools and military bases. A vaccine can help prevent infection.
  • Haemophilus influenzae (haemophilus). Haemophilus influenzae type b (Hib) bacterium was once the leading cause of bacterial meningitis in children. But new Hib vaccines have greatly reduced the number of cases of this type of meningitis.
  • Listeria monocytogenes (listeria). These bacteria can be found in unpasteurized cheeses, hot dogs and luncheon meats. Pregnant women, newborns, older adults and people with weakened immune systems are most susceptible. Listeria can cross the placental barrier, and infections in late pregnancy may be fatal to the baby.

Prevention - Bacterial meningitis

Bacteria that can cause meningitis can spread through coughing, sneezing, kissing, or sharing eating utensils, a toothbrush or a cigarette.

These steps can help prevent meningitis:

  • Wash your hands. Careful hand-washing helps prevent germs. Teach children to wash their hands often, especially before eating and after using the toilet, spending time in a crowded public place or petting animals. Show them how to vigorously and thoroughly wash and rinse their hands.
  • Practice good hygiene. Don't share drinks, foods, straws, eating utensils, lip balms or toothbrushes with anyone else. Teach children and teens to avoid sharing these items too.
  • Stay healthy. Maintain your immune system by getting enough rest, exercising regularly, and eating a healthy diet with plenty of fresh fruits, vegetables and whole grains.
  • Cover your mouth. When you need to cough or sneeze, be sure to cover your mouth and nose.
  • If you're pregnant, take care with food. Reduce your risk of listeriosis by cooking meat, including hot dogs and deli meat, to 165 F (74 C). Avoid cheeses made from unpasteurized milk. Choose cheeses that are clearly labeled as being made with pasteurized milk.
 
Some forms of bacterial meningitis are preventable with the following vaccinations:
  • Haemophilus influenzae type b (Hib) vaccine
  • Pneumococcal conjugate vaccine (PCV13)
  • Pneumococcal polysaccharide vaccine (PPSV23)
  • Meningococcal conjugate vaccine

Short-term antibiotic prophylaxis is another method of prevention, particularly of meningococcal meningitis. In cases of meningococcal meningitis, prophylactic treatment of close contacts with antibiotics (e.g. rifampicin, ciprofloxacin or ceftriaxone) can reduce their risk of contracting the condition, but does not protect against future infections.

While antibiotics are frequently used in an attempt to prevent meningitis in those with a basilar skull fracture there is insufficient evidence to determine whether this is beneficial or harmful. This applies to those with or without a CSF leak.

Diagnosis - Bacterial meningitis

The list of diagnostic tests mentioned in various sources as used in the diagnosis of bacterial meningitis includes: 

  • Lumbar puncture (spinal tap) - spinal tap to collect cerebrospinal fluid (CSF). In people with meningitis, the CSF often shows a low glucose level along with an increased white blood cell count and increased protein.
  • Blood culture - blood tests for bacteria 
  • Meningococcal rash pressure test - test a skin rash for the "failure to whiten under pressure" property of a meningococcal rash.

Prognosis - Bacterial meningitis

With prompt treatment, patients can have good recovery. However, bacterial meningitis can be fatal within days without prompt antibiotic treatment. Delayed treatment increases the risk of permanent brain damage or other complications such as seizures, hearing loss, memory difficulty and learning disabilities.

Treatment - Bacterial meningitis

Antibiotics

Empiric antibiotics (treatment without exact diagnosis) should be started immediately, even before the results of the lumbar puncture and CSF analysis are known. The choice of initial treatment depends largely on the kind of bacteria that cause meningitis in a particular place and population. For instance, in the United Kingdom empirical treatment consists of a third-generation cefalosporin such as cefotaxime or ceftriaxone. In the USA, where resistance to cefalosporins is increasingly found in streptococci, addition of vancomycin to the initial treatment is recommended. Chloramphenicol, either alone or in combination with ampicillin, however, appears to work equally well.

Empirical therapy may be chosen on the basis of the person's age, whether the infection was preceded by a head injury, whether the person has undergone recent neurosurgery and whether or not a cerebral shunt is present. In young children and those over 50 years of age, as well as those who are immunocompromised, the addition of ampicillin is recommended to cover Listeria monocytogenes. Once the Gram stain results become available, and the broad type of bacterial cause is known, it may be possible to change the antibiotics to those likely to deal with the presumed group of pathogens. The results of the CSF culture generally take longer to become available (24–48 hours). Once they do, empiric therapy may be switched to specific antibiotic therapy targeted to the specific causative organism and its sensitivities to antibiotics. For an antibiotic to be effective in meningitis it must not only be active against the pathogenic bacterium but also reach the meninges in adequate quantities; some antibiotics have inadequate penetrance and therefore have little use in meningitis. Most of the antibiotics used in meningitis have not been tested directly on people with meningitis in clinical trials. Rather, the relevant knowledge has mostly derived from laboratory studies in rabbits. Tuberculous meningitis requires prolonged treatment with antibiotics. While tuberculosis of the lungs is typically treated for six months, those with tuberculous meningitis are typically treated for a year or longer.

Steroids

Adjuvant treatment with corticosteroids (usually dexamethasone) has shown some benefits, such as a reduction of hearing loss, and better short term neurological outcomes in adolescents and adults from high-income countries with low rates of HIV. Some research has found reduced rates of death while other research has not. They also appear to be beneficial in those with tuberculosis meningitis, at least in those who are HIV negative.

Professional guidelines therefore recommend the commencement of dexamethasone or a similar corticosteroid just before the first dose of antibiotics is given, and continued for four days. Given that most of the benefit of the treatment is confined to those with pneumococcal meningitis, some guidelines suggest that dexamethasone be discontinued if another cause for meningitis is identified. The likely mechanism is suppression of overactive inflammation.

Adjuvant corticosteroids have a different role in children than in adults. Though the benefit of corticosteroids has been demonstrated in adults as well as in children from high-income countries, their use in children from low-income countries is not supported by the evidence; the reason for this discrepancy is not clear. Even in high-income countries, the benefit of corticosteroids is only seen when they are given prior to the first dose of antibiotics, and is greatest in cases of H. influenzae meningitis, the incidence of which has decreased dramatically since the introduction of the Hib vaccine. Thus, corticosteroids are recommended in the treatment of pediatric meningitis if the cause is H. influenzae, and only if given prior to the first dose of antibiotics; other uses are controversial.

Resources - Bacterial meningitis

  • NIH 


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