PMY3304- CNS INFECTION

What are most cases of bacterial meningitis and septicaemia caused by?

meningococcal bacteria

what causes septicaemia?

meningococcal bacteria multiply and produce poisons which attack blood vessel walls causing blood to leak out

what causes meningitis?

meningococcal bacteria cross from blood into lining of brain

what are the meninges?

membranes that protect the brain, there are three layers known as dura mater, arachnoid mater and pia mater

what are leptomeninges?

the two innermost layers of the meninges, arachnoid mater and pia mater

what is the function of the meninges?

protect the CNS from trauma injury, anchor the brain and provide a support system for blood vessels, nerves and lymphatic system

what is meningitis?

the inflammation of the meninges, associated with the presence of bacteria, viruses and fungi in the CNS, there is a high mortality rate and risk of serious sequelae in survivors

what is sequelae?

condition that is the consequence of a previous disease or injury

what is the most common cause of viral meningitis?

human enteroviruses

who does fungal meningitis mainly affect?

immunocompromised people 

what commonly causes fungal meningitis?

cryptococcus neoformans, which is found in the soil and candida albicans (mainly in premature babies)

what ages is bacterial meningitis common in?

the extremes of age, very old and very young

what are major causes of bacterial meningitis in neonates (<1 month)?

E. coli, streptococcus aggalactiae, listeria monnocytogenes, staphylococcus aureus

what are common causes in bacterial meningitis?

neisseria meningitidis, streptococcus pneumoniae, haemophilus influenzae type B (Hib)

what is the most common cause of meningococcal disease?

Neisseria meningitis

what is neisseria meningitis?

an aerobic, gram negative diplococcus

what is the function of the polysaccharide capsule of neisseria meningitis?

helps the pathogen resist phagocytosis and lysis

what is the most common type of meningitis in the UK and Europe?

MenB

how is N meningitidis transmitted?

most people carry N. meningitidis in their nasophorynx, usually without ill effects, however if it penetrates mucosal cells and enters the bloodstream , it can cross the BBB causing meningitis. It is transmitted via droplets or secretions from upper respiratory tract, requiring frequent or prolonged contact

how long is the incubation period of N. meningitidis?

2-7 days

what are the risk factors for meningococcal disease?

• extremes of age

• overcrowding

• smoking

• winter season

• organ dysfunction

• cancer

• sickle cell disease

• absent or non functioning spleen

• incomplete immunisation

• immunocompromised status

what is the role of the spleen?

role in immune systems filtering of bacteria and production of antibodies

what is the pathophysiology of meningococcal disease?

colonisation of nasopharynx and invasion of submucosa by overcoming host defences like physical barriers, local immunity,, phagocytes/ macrophages

Go through how meningococcal disease colonises in the body

1) invasion of blood stream

2) survival and multiplication

3) high levels of bacteriaemia

4) crossing of BBB

5) invasion of the meninges

6) bacteria induce an increased permeability of BBB

7) pleocytosis - abnormally large number of lymphocytes in CSF- host inflammatory response

8) oedema and increased intracranial pressure

9) release of proinflammatory compounds from infiltrated white blood cells and other host cells

10) neuronal injury, pus and abscess formation

what is pleocytosis?

increased cell count

what are the common, non-specific symptoms of meningitis?

• fever

• vomiting/nausea

• lethargy

• irritability

• ill appearance

• refusing food/drink

• muscle ache/ joint pain

• difficulty breathing/ respiratory symptoms

what are the less common, non- specific symptoms?

• chills/shivering

• diarrhoea

• abdominal pain/ distension

• sore throat or other ENT symptoms

what are the neurological signs of meningitis?

• bulging fontanelle

• stiff neck or back

• altered mental state

• photophobia

• kernig’s and brudzinksi’a signs 

• focal neurological deficit e.g. speech affected

What are the circulatory signs of meningitis?

• petechial/ purpuric rash (non-blanching)

• limb pain

• cold hands or feet

• unusual skin colour

• capillary refill time is more than two seconds

• shock and hypotension

what is a petechial/purpuric rash?

• starts as a cluster of pinprick blood spots (petechiae) that spread to form bruises under the skin (purpurae)

• they don’t blanch under pressure

• any patient with a petechial/ purpuric rash should be referred

what are signs and symptoms of meningitis in infants?

• absent

• fever, but cold hands and feet

• high pitched moaning or whimpering

• blank staring, inactivity, difficult to wake up

• poor feeding

• neck retraction with arching of back 

• pale and blotchy complexion

what is the prognosis of meningitis?

it spreads rapidly so if untreated can be fatal, complications can be neurological, physical, hydrocephalus, reduced quality of life, learning difficulties, emotional and behavioural difficulties

what are the potential neurological symptoms of meningitis?

hearing loss, seizures, cognitive impairment, motor deficits, visual impairments 

what are the potential physical complications of meningitis?

amputations, skin, scars

what is hydrocephalus?

accumulation of CSF in the brains ventricles

where is the diagnosis confirmed?

confirmed in secondary care by physical examination, monitoring vitals

what is assessed to confirm the diagnosis of meningitis?

consciousness level using Glasgow Coma Scale (GCS) or AVPU, HR and BP, RR, O2 sats, temperature, capillary refill time, blood tests for CRP and WBC, lumbar puncture with examination of CSF

Where is the CSF drawn from?

drawn from between the two vertebrae

what are the CSF features of bacterial meningitis?

• raised opening pressure (>20)

• appearance will be turbid, cloudy, purulent

• CSF white blood cell count will be raised typically >100

• predominant cell type is neutrophils

• CSF protein will be raised 

• CSF glucose and plasma: glucose ratio will be very low 

How should meningitis be managed?

1) urgent antibiotic treatment

2) adjunctive therapy

3) supportive therapy

how do you decide what antibiotic should be given for meningitis?

the antibiotic needs to be able to reach therapeutic conditions in the CSF, empiric therapy should be used to treat suspected meningococcal disease

what should be given to patients with suspected meningitis before urgent transfer to hospital?

a single dose of benzylpenicillin sodium (cefotaxime in penicillin allergy)

what antibiotic should be given when the causative organism is meningococci?

benzylpenicillin sodium or cefotaxime and suggested duration is 7 days

what antibiotic can be given if the causative organism is pneumococci?

cefotaxime (and dexamethasone), duration of 14 days

what antibiotic should be given if the causative organism is H.influenzae?