Bacterial meningitis

MENINGITIS is a rare but serious infection of the brain and spinal cord membranes (meninges),^1,2 which, if left untreated, can be fatal in up to 50% of cases.³ Meningitis can be caused by infective pathogens such as viruses, fungi or bacteria, or by non-infective means such as certain cancers, autoimmune disorders and injury. 

Several different types of bacteria can cause meningitis, though the most common causes are Streptococcus pneumoniae, Haemophilus influenzae type b (Hib), and Neisseria meningitidis.^1,2 Infections caused by N. meningitides are known as meningococcal disease, and infections from S. pneumoniae are referred to as pneumococcal disease. 

While meningitis is rare, Ireland has the highest prevalence of meningococcal disease in Europe.⁴ On average there are 200 cases of meningitis in Ireland each year.⁴ About half of all cases occur in children aged under five years of age⁴, with approximately one in 12 cases in children and one in five cases in adults resulting in death.² The epidemiology of bacterial meningitis has changed considerably over the past two decades due to the introduction of widespread vaccination programmes. The Hib vaccine has reduced cases by more than 99%.² This decline is most obvious in the youngest (children aged two years and younger have reduced by 64%) and the oldest (those older than 65 years have reduced by 54%).²

Bacterial meningitis is transmitted person-to-person through droplets of respiratory or throat secretions from carriers.³ The virus does not survive for long outside of the body and is therefore generally only passed on to people through close or prolonged contact. The average incubation period is four days but can range anywhere between two and 10 days.³

Risk factors

The bacteria that cause meningitis are common and are present in the upper respiratory tract.¹ It is estimated that 5-11% of adults and 25% of adolescents are carriers. That is that they have the bacteria in their throat or nose without any signs or symptoms of illness.⁵ It is only when the bacteria are acquired by a susceptible person that this causes invasive disease.¹

It is not fully understood why some people are more vulnerable to developing meningitis. Key risk factors however include age (those younger than five or older than 65 years of age), non-immunised infants, people who have no spleen (increases the risk of overwhelming bacterial infection), people with reduced immune system function or underlying medical conditions (such as sickle cell disease).²

Environmental effects can also have an influence on the development of meningitis. These factors include the particular season (meningitis is more common in the winter months), lower socio-economic status, exposure to pathogens (such as having a close contact who has meningitis), smoking, and living in ‘closed’ or ‘semi-closed’ communities such as university halls or military barracks.⁵

Complications

Acute bacterial meningitis is one of the top 10 causes of infection-related death worldwide. For those who survive 30-50% experience permanent neurological damage ranging from minor coordination and movement problems, to epilepsy, paralysis and severe mental impairment.⁴ Although overall mortality has fallen in recent years, the rate of complications have not. 

The most common complications are: hearing loss (33.6%), seizures (12.6%), motor deficit (11.6%), cognitive impairment (9.1%), hydrocephalus (7.1%) and visual disturbance (6.3%). 

In the most severe cases, meningitis can result in brain damage through injured or destroyed nerve cells; the nerve cells become damaged from poisons produced by the bacteria, the increased pressure on the brain and reduced blood supply.⁴ If septicaemia develops, blood clots can develop, which restricts oxygen to tissues, resulting in necrosis. This can lead to widespread scarring and even the need for limb amputation. 

During the first few days of treatment it is often possible to determine whether there will be any permanent damage, and in most cases any serious problems become apparent while the patient is still in hospital.⁴

Prevention

Currently, there are three main types of vaccinations freely available to the public to prevent meningococcal disease.³ These are:

•
Polysaccharide vaccines, which cover combinations of A, C, Y and W forms

•
Meningococcal conjugate vaccines, which protect against group C 

•
The most recently developed Bexsero vaccine, which protects against capsular group B3.

There is also a vaccination available to protect against pneumococcal disease called PCV (pneumococcal conjugate vaccine), which can target up to 13 of the most prevalent serotypes.⁶ Vaccination against meningitis is provided with the routine childhood immunisation programme. For further information see: www.hse.ie/eng/health/immunisation/hcpinfo/guidelines/immunisationguidelines.html

Adverse reactions

Adverse reactions following immunisation are common. Pain, tenderness, swelling or redness at the injection site are common in all age groups. Crying, irritability, drowsiness, impaired sleep, diarrhoea and vomiting are commonly seen in infants and toddlers, and muscle pains (myalgia), headaches and drowsiness are frequently seen in older children and adults. Neurological reactions such as dizziness, febrile seizures, faints and numbness following MenC conjugate vaccination are very rare.⁵

Diagnosis

Diagnosing meningitis can be difficult as it normally presents with common, non-specific features. The classic symptoms of meningitis are: a non-blanching rash, a stiff neck, unusual skin colour, shock and hypotension, slow capillary refill time (resulting in cold hands and feet) and back rigidity.

However those at the highest risk such as the very young, old and immunocompromised may not have these ‘classic’ symptoms and instead tend to present with so-called ‘atypical’ or non-specific symptoms. Common non-specific symptoms include: fever, nausea/vomiting, lethargy, irritability, ill appearance, headache, refusing food and drink, muscle aches and respiratory signs. 

The very nature of these non-specific symptoms can make it difficult to rule out other possible viral infections such as enteroviruses. It is therefore imperative that a careful history should be taken including immunisation history. Clinical judgment should be used, taking into account parental or carer concern relating to the progression of the illness and overall severity.

Assessment

If bacterial meningitis is suspected, it is important to check and document the following vital signs: conscious level, heart rate and blood pressure, respiratory rate, temperature and capillary refill time. The person should also be closely monitored for any signs or features of shock such as unusual skin colour, tachycardia, hypotension, respiratory problems, leg pain, altered mental or toxic state, or poor urine output. 

If a rash is present, it may appear as a scanty petechial rash (red or purple non-blanching macules smaller than 2mm in diameter) or a purpuric rash (spots larger than 2mm in diameter). The rash is most typically associated with meningococcal meningitis, and is noted in 80-90% of patients.²

The rash normally appears between four to 18 hours after the initial symptoms of illness, but the disease can be in the advanced stages before the rash starts to appear, and a rapidly evolving petechial or purpuric rash is a sign of very severe infection. 

If meningitis is suspected, all cases should be urgently referred to secondary care as an emergency by dialling 999.¹

Management

For cases where a non-blanching rash is present, parental (IV) antibiotics should be given at the earliest opportunity, provided this does not delay referral. 

In cases where a rash is not present, antibiotics should not be given unless urgent referral is not possible; delaying antibiotic administration until the patient is in secondary care is recommended in less severe cases as the rate of progression of the disease is slower when compared to septicaemia. 

For all cases, a lumbar puncture should be performed in secondary care to extract cerebrospinal fluid (CSF) unless this is contraindicated. CSF is used to confirm diagnosis and determine what bacteria are present, which will ensure that the appropriate antibiotic is used.^1,3 

Although the initial diagnosis can be made following a clinical examination it is impossible to differentiate between viral and bacterial meningitis without a culture of CSF.

Once admitted, patients should be closely monitored for signs of deterioration as meningococcal disease can worsen rapidly, regardless of any initial assessment of severity.¹

While the risk to close contacts is low, and 97% of cases are isolated incidents,⁴ households of those who have developed the infection are at higher risk of developing the disease. 

The risk is highest in the first seven days following onset, and can persist for at least four weeks.⁵ This risk of meningitis can be reduced by providing prophylactic treatments to those people identified as being at high risk.

These include people who have had prolonged contact with the original index case in a household or those who have been exposed to large particle droplets/secretions from the respiratory tract of the infected individual. 

A seven day course of prophylactic antibiotics² should be provided to close contacts of the patient as soon as possible, ideally within 24 hours of diagnosis, and vaccinations arranged where necessary. The MenB vaccine however is not currently recommended as a prophylactic treatment for household contacts of an index case or for contacts in an educational setting.⁵

It is important to note that meningitis is a notifiable disease in Ireland, and all cases should be reported to the director of public health/medical officer of health for the area of residence of the patient.⁷

Follow up

Individual care plans should be created for the patient before they leave hospital to coordinate rehabilitation when it is needed.⁴ Once discharged, all patients should be monitored closely and assessed for any signs of complications.¹ Children and young people who have had bacterial meningitis should be offered a review by a paediatrician, with their hearing tested either before or within four weeks of discharge.

This is especially important as it provides an assessment of their need for a cochlear implant, which if required, should be placed as soon as the child has recovered from the acute stage of the disease.² Other complications considered during this assessment should include cognitive impairment, seizures, motor problems, hydrocephalus, visual disturbances and renal failure. 

Information and support should be provided to the person and family members from support groups and charities; some people may also find it helpful to talk with someone who has been through a similar situation. Support groups such as Meningitis Research Foundation (www.meningitis.org/ireland) and Act for Meningitis (http://actformeningitis.ie/) provide support services and helplines for those affected by the disease. 

References

1. National Institute for Health and Care Excellence. Meningitis (bacterial) and meningococcal septicaemia in under 16s: recognition, diagnosis and management [CG102]. Published 2010. Available from: https://www.nice.org.uk/guidance/cg102/chapter/Introduction [Accessed August 29, 2016]
2. BMJ Best Practice. Bacterial meningitis. Published 2016. Available from: http://bestpractice.bmj.com [Accessed August 29, 2016]
3. WHO. Meningococcal meningitis. Published 2015. Available from: http://www.who.int/mediacentre/factsheets/fs141/en/ [Accessed August 29,2016]
4. Meningitis Research Foundation. http://www.meningitis.org/ireland [Accessed August 29, 2016]
5. PHE. The Green Book. Meningococcal. Published 2016. Available from: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/545629/Green_Book_Chapter_22.pdf [Accessed August 29, 2016]
6. WHO Pneumococcal disease. Published 2014. Available from: http://www.who.int/immunization/diseases/pneumococcal/en/ [Accessed August 29, 2016]
7. Health Protection Surveillance Centre. Published 2016. Available from: http://www.hpsc.ie/NotifiableDiseases/Whotonotify/