Week 12 - Meningitis Flashcards
What is meningitis
Inflammation of the meninges (tissue surrounding the brain)
What are the causes of meningitis
- Bacterial
- Viral
- Fungal
- Parasitic
- Trauma
List the potential bacterias that can cause bacterial meningitis
All of them can be found in many diff. places of the body
- Streptococcus / Strep.
- Streptococcus pneumonaie
- gram-POSITIVE
- has a CAPSULE
- non-motile
- non-spore forming
- diplococcus (presents as 2 joined cells) - Neisseria menningitidis
- gram-NEGATIVE
- has a CAPSULE
- non-spore forming
- non-motile - Heamophilius influenzae B (HIB)
- gram-NEGATIVE
- may have CAPSULE
- non-motile
- non-spore forming
- NOTE: doesnt cause influenza
Pathogenesis of Bacterial Meningitis: how the bacteria causes meningitis
- Nasopharynx colonisation + adherance
(nasal / pharynx ~ top of throat)- bacterias are usually found here
- can be exposed to bacteria but does NOT mean will get meningitis
- bacteria binds to IG receptors on host membrane surface
- Invasion of Intravascular space
- via transcytosis
- Survival in the bloodstream
- this is how sepsis can occur
- bacteria has to overcome host defence mechanisms to survive which the capsule enables
- Cross the BBB
- via transcytosis through BBB
- bacteria binds to surface host = increased expression of PAF receptor
- PAF receptor binds to ligand on bacteria cell wall = endocytosis of bacteria
- bacteria is released into CSF - Survival in the subarachnoid space
- bacteria can survive due to minimal immune defence in CSF
- bacteria multiplies in CSF (CSF contains all nutirents required for this)
- Immune activation and Inflammation
- ↑ no. of bacteria alerts immune system = send WBC etc. = build up of pressure around brain = INFLAMMATION + brain damage
- Brain damage due to activated leucocytes releasing MMPs (enzyme) which causes direct tissue damage
Transmitted to other via droplets
- e.g. snezzing, coughing
What are the risk factors for bacterial meningitis
- Age
- is a disease of children (form newborns to older adults)
- Underlying illness
- If recently travelled to a country with high prevelance of cases
- Smoking
Explain the epidemiology of bacterial meningitis
epidemiology - occurence, distribution (spread) and control of diseases
- Viral meningitis isn’t as serious as bacterial
- Bacterial meningitis in UK has become rare
- due to development of vaccines
- rare but severe disease
- prevelance has declined over last 20 years
- Higher incidence in parts of Africa (known as meningitis belt)
What are the symptoms and complications of bacterial meningitis
SYMPTOMS:
- Rash
- Fever
- Vomitting
- Headache
- Stiff Neck, severe muscle pain
- Photosensitivity (bright light causes discomfort)
- Convulsions / seizures
- Drowsy
- Babies: unusal cru, bulging fontanelle
COMPLICATIONS:
- Death
- Brain damage
- Loss of hearing
- Loss of limbs / disabilities
- Cognitive impairments
- Learning difficulties
- Paralysis
- Generalised weakness
How is meningitis diagnosed
- Diagnostic tests
- lumbar puncture to sample CSF
- IF CSF: cloudy, ↑ WBC count (neutruophiils), ↑ CRP (protein = inflammation), ↓ glucose levels, gram staining
- Culture and Sensitivity Testing
- determine if bacetria species is -ive or +ive
- result tdetermine antimicrobial treatment
- grow CSF sample on agar plates
- Joint tests (patient lays flat on back)
- when lift head up, the knees will also involuntarily lift up = BRUDZINSKI
- when leg is raised in air will feel a lot of pain / discomfort if try to straighten it = KERNIG
- Tumbler (glass) test
- if patient has a non-blanching rash
- when roll glass over rash if area doesnt go white / lose its colour = sign of sepsis
- Blood tests
- see if bacterial or viral
- looking for inflammation markers e.g. CRP, WBC, neutrophils - CT scan
- check for swelling - Buildup of fluid in subarachnoid space
- Buildup of pus (dead white cells) in subarachnoid space
- Inflammation of walls + blood vessels
- Obstructed CSF flow (due to buildup)
How is bacterial meningitis treated: NICE
Will start broad spectrum antibiotics once it is suspected (started before diganosis is confirmed as it can be life-threatening)
Treatment:
(in hospital)
- IV Antibiotics (10 days):
- 3 months + = IV ceftriaxone
- 3 months = Cefotaxime plus amoxicillin or ampicillin (oral, non-IV)
- amoxocillin not given on own due to poor CNS penetration
BOTH are cephlosporins
- Steroids:
- may be given to reduce inflammation / swelling
- IV Fluids
- Analgesics
- for pain releif, headaches
DISCHARGED When:
- Clinical improvement i.e. temp < 37ºC
-
NOTE:
Can treat viral meningitis at home (unless its severe)
- take painkillers, anti-sickness
- get plenty rest
What are virulence factors involved in bacterial meningitis
- Capsule
- is a polysaccaride that surrounds disease causing organism
- hard for immune system / WBC to deal with as it has strong antiphagocytic properties
- Pneumolysin
- binds to IgG and inactivates it
- enhances bacteria survival - IgA1 protease
- Psp (pneumococcal surface proteins)
How can we prevent bacterial meningitis
- Vaccinations
- Good personal hygiene
- Drinking pure water
- Healthy diet
- Vitamins
What are the vaccinations in place to prevent bacterial meningitis (in UK)
8 Weeks:
- Hib (H.influnzae B) vaccine
- intoruduced in 1993
- MenB (N.meningitidis)
- PCV (pneumococcal conjugate vaccine)
- capuslar vaccine
- conjugated to a protein to elicit protective immune response (if inject child with polysaccharide = bad immune response)
- conjugated vaccine ↑ immunogeneicity (in children)
12 weeks:
- Hib
16 weeks:
- MenB
1 yo:
- MenB booster
65 yo:
- PPV (pneumococcal polysaccharid vaccine)
- not conjugated
- targets pneumonia not meningitis
