What is Bacterial Meningitis (Meningitis)?
Bacterial meningitis is when the protective layer around the brain and spinal cord, called the meninges, gets infected by bacteria, leading to inflammation. It’s a severe and potentially fatal condition that demands quick identification and treatment.
What Causes Bacterial Meningitis (Meningitis)?
Bacterial meningitis is an inflammation of the brain and spinal cord coverings, caused by bacterial infection. This can occur from bacteria that enters the body and travels through the bloodstream or spreads from a nearby infection. Bacteria causing this condition can either come from within the community or from a hospital setting.
Different types of bacteria are responsible for this condition depending on a person’s age. For example, Group B Streptococcus bacteria commonly cause this condition in infants under 2 months old, while Streptococcus pneumoniae bacteria most often cause it in all other age groups. The exception is in ages 11 to 17, where Neisseria meningitidis bacteria is the most common cause.
Other less common culprits of bacterial meningitis include Listeria monocytogenes and several strains of bacteria like Escherichia coli, Klebsiella, Enterobacter, and Pseudomonas aeruginosa. Hemophilus influenzae bacteria can sometimes cause meningitis in people who have not been vaccinated. Hospital-acquired infections are typically due to S. pneumonia, Staphylococcus aureus, Staphylococcus albus, and some types of gram-negative bacteria.
Data gathered from 2003 to 2007 stated that among 1670 cases of meningitis in the U.S., S. pneumoniae bacteria was the most common cause (58.0%) of the disease, followed by Group B Streptococcus (18.1%), N. meningitidis (13.9%), H. influenzae (6.7%), and L. monocytogenes (3.4%).
In addition, infectious meningitis could be caused by viruses, fungi, and protozoa. Some types of meningitis might not be infectious and could be caused by cancer, medicines, or inflammatory conditions.
Risk Factors and Frequency for Bacterial Meningitis (Meningitis)
Bacterial meningitis used to be more common in children, but due to the development and use of vaccines, it has become less prevalent. Vaccines have also changed the microorganisms that cause the disease and increased the median age of those infected. In 2006, there were 72,000 hospital stays related to meningitis in the United States, with majority of these cases being caused by a virus.
- Viral infections: 54.6%
- Bacterial infections: 21.8%
- Fungal and parasitic infections: 7.3%
- Unspecified cause: 17.2%
Unfortunately, 8% of people in the hospital with bacterial meningitis died. This rate significantly increased for those older than 45. However, the yearly number of meningitis cases in the United States has dropped from 2.00 per 100,000 people in 1998-1999 to 1.38 per 100,000 people in 2006-2007. At the same time, the average age of patients increased from 30.3 to 41.9. Even more promising, there has been a steady decline in meningococcal disease, a type of bacterial meningitis, since the late 1990s. In 2017, only about 350 cases were reported across the country.
Several risk factors for bacterial meningitis have been identified. Individuals are at a higher risk if they have an abnormal link between the nasopharynx and the subarachnoid space (areas in your head), whether it’s a birth defect or a result of an accident. Having had brain surgery, skull fractures, or cochlear implants also increases the risk. People with weakened immune systems and those living in close quarters like college dorms or military barracks are also more vulnerable.
Signs and Symptoms of Bacterial Meningitis (Meningitis)
Meningitis is a disease where the tissues around the brain and spinal cord become inflamed. While the most common symptoms are fever, a stiff neck, and changes in mental state, such as confusion, these are present in only 41% of bacterial meningitis cases. These symptoms are more likely in older patients. At least one of these symptoms will be experienced by 70% of patients. Other early symptoms can include headaches, increasing confusion, drowsiness, specific nervous system symptoms (focal neuro deficits), and seizures.
Doctors will usually ask about any recent operations on the brain or spine, vaccination history, and living conditions. They will also perform a physical examination, possibly finding neck stiffness or positive signs of Kernig or Brudzinski. It’s important to note, though, that not finding these signs doesn’t mean the patient doesn’t have meningitis.
Brudzinski’s sign is when the patient’s knee bends involuntarily when the neck is gently bent forward. Kernig’s sign is when extending the patient’s knee causes resistance or pain when the patient is lying flat with the hip bent to a right angle. These signs indicate that the tissues surrounding the brain and spinal cord may be irritated. A check of the patient’s eyes may show swelling of the optic nerve due to increased pressure inside the skull. A rash that spreads quickly and looks like tiny purple or red spots, known as purpura fulminans, might indicate an infection with meningococcus bacteria.
- Fever
- Stiff neck
- Changes in mental state (like confusion)
- Headache
- Increasing confusion
- Drowsiness
- Specific nervous system symptoms
- Seizures
- Brudzinski’s sign (knee bends involuntary when neck is bent)
- Kernig’s sign (resistance or pain when extending the knee)
- Swelling of the optic nerve (indicating increased skull pressure)
- Fast-spreading purpura fulminans rash (indicating bacterial infection)
Testing for Bacterial Meningitis (Meningitis)
When bacterial meningitis is suspected, doctors typically perform a procedure called a lumbar puncture. In this procedure, a sample of cerebrospinal fluid (CSF), which surrounds your brain and spinal cord, is taken for testing. Tests may include a Gram stain (to look for bacteria under a microscope), a culture to grow any bacteria present, a cell count, and tests to measure the glucose (sugar) and protein levels in the fluid.
In bacterial meningitis, the fluid usually has a high protein level, a low glucose level, and a high number of immune cells, specifically a type of white blood cell called a neutrophil. It’s worth noting that because the glucose level in the CSF depends on the glucose level in the blood, the ratio of glucose in the CSF to the glucose in the blood is considered a more reliable measure for diagnosing bacterial meningitis than the absolute glucose level in the CSF itself.
Bacterial meningitis is confirmed when bacteria are seen under the microscope or are grown in the culture. Before doing a lumbar puncture, doctors may carry out a CT scan of the patient’s head without using a dye (a non-contrast CT scan), especially if the patient has any risk factors that might suggest their brain is under increased pressure. These risk factors can include symptoms like new-onset seizures, a specific type of eye sign known as papilledema, specific neurological issues, or a weakened immune system.
Sometimes, a lumbar puncture may be delayed. For instance, this can happen if the patient’s vital signs are unstable, they have abnormal blood clotting, or they’ve recently had a seizure. If testing is delayed, the doctor will start treatment with antibiotics right away because bacterial meningitis is a serious, life-threatening condition. In such cases, blood samples are typically taken to be cultured, since more than half of people with bacterial meningitis have bacteria present in their blood. Tests may also be done to measure the levels of certain proteins, such as C-reactive protein or procalcitonin, as these are typically higher when the cause of the meningitis is bacterial rather than viral.
Treatment Options for Bacterial Meningitis (Meningitis)
It’s crucial to administer antibiotics as quickly as possible when dealing with bacterial meningitis. If treatment is delayed by 3 to 6 hours, the patient’s chances of survival drop dramatically. What type of antibiotic is used depends on the bacterial strain causing the infection.
If the diagnosis is likely to take some time, doctors might begin treatment immediately with antibiotics such as ceftriaxone and vancomycin. Patients who are over 50 or have weakened immune systems should also be given ampicillin.
For people with bacterial meningitis due to a head trauma or after a neurosurgical procedure, there’s a need for treatment against specific bacteria that are resistant to multiple drugs and aerobic gram-negative organisms. Effective antibiotics in such cases could be vancomycin and ceftazidime, or cefepime. The antiviral drug acyclovir could be used to cover for Herpes Simplex Virus (HSV).
Once the type of bacteria causing the infection is confirmed by lab results, the antibiotic treatment can be adjusted to target the specific strain.
Dexamethasone, a type of steroid medication, might improve survival rate when given alongside antibiotics in cases of S. pneumoniae infections. However, it doesn’t seem to increase chances of recovery in meningitis caused by other types of bacteria.
Patients suspected of having meningitis caused by a specific bacteria, Neisseria meningitidis, should be kept away from others until they’ve had at least 24 hours of antibiotics. This is called ‘droplet precautions’ and helps to prevent the disease from spreading.
Close contacts of the patient should also receive preventative (prophylactic) treatment. This could include ciprofloxacin, rifampin or ceftriaxone. ‘Close contacts’ are defined as anyone who has been within about 3 feet of the patient for more than 8 hours in the week leading up to and 24 hours after the patient started antibiotics. This also includes anyone exposed to the patient’s saliva or other oral secretions during this time.
What else can Bacterial Meningitis (Meningitis) be?
When it comes to altered mental states and comas, doctors need to consider various potential causes:
- Brain Abscess: An infection in the brain that causes an accumulation of pus.
- Brain Tumors: Abnormal growths in the brain.
- Central Nervous System (CNS) Vasculitis: Inflammation of the blood vessels in the brain or spine.
- Delirium Tremens (DTs): A severe form of alcohol withdrawal causing confusion and hallucinations.
- Subarachnoid Hemorrhage: A type of stroke caused by bleeding on the surface of the brain.
- Encephalitis: Inflammation swelling of the brain usually due to a viral infection.
- Herpes Simplex Virus (HSV) in Emergency Medicine: A viral infection affecting the brain.
- Leptospirosis: A bacterial infection that can cause a wide range of symptoms, including changes in mental state.
- Meningeal Carcinomatosis: Cancer that has spread to the membranes surrounding the brain and spinal cord.
- Noninfectious Meningitis: Inflammation of the membranes surrounding the brain and spinal cord, not caused by an infection, sometimes due to medication.
- Pediatric Meningitis and Encephalitis: Inflammation of the brain or surrounding tissues in children, due to infection.
- Stroke: A condition that occurs when blood flow to part of the brain is cut off.
- Subdural Empyema: A collection of pus between the brain and its outer covering, usually due to a bacterial or fungal infection.
Upon identifying these possibilities, the healthcare provider would conduct suitable tests to ensure an accurate diagnosis.
What to expect with Bacterial Meningitis (Meningitis)
The death rate for bacterial meningitis is approximately 10-15%. The key to survival lies in early identification and treatment of this condition, which typically involves the use of appropriate antibiotics. If treatment is delayed, it can lead to increased pressure inside the skull, reducing blood flow to the brain. This could quickly lead to unconsciousness and possibly death.
Possible Complications When Diagnosed with Bacterial Meningitis (Meningitis)
About a quarter of people with meningococcal disease may experience complications. These complications can also occur in other types of bacterial meningitis and may range from mild to severe. Some people may face temporary issues while others may deal with permanent ones. Delays in treatment can lead to inflammation of the blood vessels in the brain, leading to a stroke. Some other long-term complications may include:
- Seizures
- Memory and concentration problems
- Issues with movement, balance, and coordination
- Learning difficulties
- Speech problems
- Vision loss
- Hearing loss
