Prevention Strategies For Bacterial Meningitis

Overview

Meningitis is described as an inflammation, which occurs on the membranes that protect the brain and spinal cord, known as meninges, and it is caused by an infection.^1,2 There are two types of meningitis, namely, viral meningitis and bacterial meningitis.¹ Viral meningitis is usually caused by different viruses, but most commonly it is caused by enteroviruses (EVs) (kohil). Viral meningitis typically has a very good prognosis and the treatment is relatively simple without the need for hospitalisation.^2,3 On the other hand, bacterial meningitis is considered a life-threatening infection, which affects 1.2 million people every year and is responsible for 135,000 deaths yearly.³ The situation is worse for low-income countries, where the incidence rate is 80 per 100,000 people compared to the high-income countries' incidence rate of 0.9 per 100,000 people.⁴ Moreover, in low-income countries, 54% of individuals die of the disease and approximately 24% are shown to acquire neurological complications, such as speech, vision and hearing problems.⁴ 

Causes of bacterial meningitis 

Several types of bacteria cause bacterial meningitis. The study provided a detailed report on which bacteria is responsible for causing bacterial meningitis in different age groups and regions by reviewing the available studies.⁵ Overall, the infection was mainly caused by three bacteria species, specifically Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae. S. pneumoniae was found to cause bacterial meningitis in children between the ages of 6 and 18 and in newborns in all regions. For the newborns in Africa, the main pathogens for the infection were S. pneumoniae and Escherichia coli. In Europe, children in the age group 1-5 years were mainly infected by N. meningitidis. Before the vaccine was developed H. influenzae was the leading pathogen to cause bacterial meningitis.⁶ Despite this, in low-income countries, where vaccination is limited, it remains a significant bacterium to cause the disease.⁶ 

The infection that causes meningitis can get to our body typically through the respiratory system, but it also can be an entering infection when bacteria access the gastrointestinal tract.^7,8 For example, through contaminated water and food.⁷ Bacterial meningitis is also divided into types based on how it was acquired. If the person develops it spontaneously within the community, it is known as community-acquired meningitis. However, if it was a result of hospitalisation due to some operations or head trauma, it is called nosocomial bacterial meningitis.⁸

Symptoms of bacterial meningitis

The symptoms or clinical signs and presentation of bacterial meningitis that are seen in patients are usually as follows:^{9, 10}

• Fever
• Anorexia
• Vomiting 
• Fatigue
• Dizziness 
• Purpuric rash
• Neck stiffness
• Severe headache 
• Photophobia 
• Confusion 
• Abnormal behaviour 
• Drowsiness
• Sometimes seizures 

Complications of bacterial meningitis

Besides bacterial meningitis being responsible for many deaths, in surviving patients, it can also lead to many severe complications, including:^{11, 12, 13, 14} 

• Sensorineural hearing loss
• Motor deficits 
• Epilepsy
• Developmental delay 
• Seizures 
• Stroke 
• Hydrocephalus
• Vision loss
• Cognitive and behavioural issues 
• Cerebral venous thrombosis (CVT)
• Septicaemia
• Respiratory failure 
• Circulatory failure 
• Other organ failure (e.g., liver, kidney, gastrointestinal complications)

Moreover, researchers have been exploring the link between bacterial meningitis and dementia, as well as neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and Huntington’s disease.⁶ The bacteria can cause neuronal damage, which can increase the risk for the development of the neurodegenerative condition.⁶ In addition, bacteria and their components and our immune system in response to infection can induce vasculitis, intravascular coagulation, ischemic, apoptotic burst in the hippocampus, and necrotic brain injury in the cortex.⁶

The complications associated with bacterial meningitis were shown to be a significant determinant of the disease outcome. For example, scientists showed that seizures as a complication of bacterial meningitis, can be a risk factor for subdural empyema, brain abscess, septic sinus thrombosis and ventriculitis.¹¹ While gastrointestinal complications were associated with lethal outcomes.¹¹ A different study showed that the lethal outcomes were observed in patients with respiratory failure, circulatory failure and other organ failure, including gastrointestinal failure, as well as with central nervous system complications, specifically, brain herniation, brain injury, and intractable seizures.¹⁴

Risk factors for developing bacterial meningitis

Scientists explored the possible risk factors that lead to a higher predisposition to acquiring bacterial meningitis. For example, the risk factors that increase the possibility for new-borns to develop bacterial meningitis include:¹⁵

• Prolonged rupture of membranes 
• Maternal vaginitis
• Asymptomatic bacteriuria
• Prematurity 
• Low birth weights 
• Asphyxia 

In adults, different risk factors were established that increase the susceptibility to bacterial meningitis. Those include:^{16, 17}

• Alcoholism
• Diabetes
• Cerebrospinal fluid leakage
• History of cancer 
• History of cardiac failure
• Immunosuppressant drug use
• History of chronic renal failure
• History of splenectomy
• Human immunodeficiency virus (HIV)
• Indoor air pollution
• Overcrowded houses 
• Malnutrition
• Sickle cell anaemia

In addition, in a different study, researchers also found that gender correlates with the risk of developing bacterial meningitis in adults. They discovered that men have a higher risk of acquiring the disease, which is potentially because men are more exposed to smoking, alcohol and illnesses that weaken the body. Together these factors increase the susceptibility to infections.¹⁸

Scientists also explored recurrent bacterial meningitis, but the exact risk factors were not identified. However, they noted some predisposing factors that were associated with developing recurrent bacterial meningitis, such as:¹⁹

• Ear or sinus infections
• Cerebrospinal fluid leakage

Prevention strategies for bacterial meningitis 

From the above, it is possible to see that bacterial meningitis is a devastating infection, making it a significant issue within the medical industry. Therefore, the invention and introduction of prevention strategies are of great importance. Currently, there are two main strategies to prevent this disease:

• Vaccination 
• Chemoprophylaxis

The main prevention strategy, which was found to be very effective against the development of neurological complications, is the vaccination routines for infants and children.²⁰ There are vaccines developed and available for the main bacteria species that cause meningitis. The Hib conjugate vaccine (HibCVs) protects against Type B H. influenzae.^{20, 21} When it comes to the N. meningitidis, there is also a conjugate vaccine against the A, C, W and Y groups, known as NmCVs.^{20, 21} However, for Group B N. meningitidis, there are two licensed vaccines available, but they are protein-based vaccines instead of conjugated vaccines.^{20, 21} Furthermore, the vaccines against S. pneumoniae are also conjugated-type vaccines. There are three vaccines currently developed and available, namely, PVC 10, PVC 13 and PVC 23. The numbers indicate the amounts of groups of S. pneumoniae against which the vaccine will protect. The PVC 1- and PVC 13 are used routinely for children.²⁰ Whereas, PVC 23 is only used in adults, which have a high risk of developing bacterial meningitis. 

Moreover, scientists are developing an improved version that will include 24 groups of S. pneumoniae.²¹ The inclusion of many groups of S. pneumoniae is very important since there are more than 90 groups of this bacteria in total.²⁰  These vaccines against the three bacterial species showed a great decline in bacterial meningitis worldwide.^{22, 23} A different vaccine was developed to specifically target group A N. meningitidis, which was affecting many people in the sub-Saharan area of Africa. The vaccine is another conjugated one, known as MenAfriVac. The vaccination program was introduced using this vaccine for 1-29 years old individuals, as well as for infants and toddlers. The MenAfriVac was found to be very effective in preventing the development, carriage and spread of bacterial meningitis, leading to the almost complete disappearance of this group-type infection.²⁴ 

Although vaccines ensured great progress in battling bacterial meningitis, some challenges are yet to be overcome, such as:^21,25

• The evolving different groups of bacteria
• Other bacterial species, which cause the disease but cannot be tackled with vaccines 
• Access to affordable vaccines in low-income countries 

Another strategy that is significant in preventing bacterial meningitis is known as chemoprophylaxis. In this strategy, chemoprophylactic antibiotics are employed. They are administered to individuals who were in close contact with other individuals or individuals diagnosed with bacterial meningitis.²⁶ For example, for H. influenzae, the antibiotic rifampin is mainly prescribed.²⁶ Whereas, in the case of N. meningitis and S. pneumoniae, ceftriaxone and ciprofloxacin are available, as well as rifampin.^{20, 26, 27}  In addition, antibiotics are used for people to prevent bacterial meningitis as a secondary disease, usually for high-risk individuals who at first underwent treatment for a different infection.⁵

Summary 

Meningitis is described as an inflammation that occurs on the membranes that protect the brain and spinal cord, known as meninges, and is caused by infection. Bacterial meningitis is considered a life-threatening infection, which affects 1.2 million people every year and is responsible for 135,000 deaths yearly. Therefore, it is essential to follow the recommended prevention strategies to minimise the spread of disease. The main and most important ones are the vaccination programs, as well as ensuring to complete the chemoprophylaxis for individuals being in close contact with patients diagnosed with bacterial meningitis and high-risk individuals.