Meningitis Flashcards
Why must meningitis be urgently diagnosed ?
It is close in proximity to the brain and spinal cord. Damage to these areas can cause serious neurological damage or potential death.
What conditions mimic Meningitis?
Conditions such as sub-arachnoid haemorrhage and stroke mimic Meningitis.
Outline the steps in diagnosing Meningitis?
- Lumbar puncture
- Processing of the CSF
- Appearance of the sample
- Cell count
- Centrifugation
- Gram stain and microscopy
- Culture
- Further tests based on microscopy results
How is a lumbar puncture carried out and what is its purpose?
a. Allows samples of cerebrospinal fluid to be obtained
b. A spinal needle is inserted between the 3rd and 4th lower vertebrae to obtain samples.
Where is a lumbar puncture sample taken from?
Between the 3rd and 4th lower vertebrae.
Outline what happens with each of the 4 lumbar samples taken to diagnose Meningitis.
- Chemistry, serology
- Gram staining, AFB staining, India ink preparation, bacterial / fungal culturing, culture for tuberculosis
- Total cell count, differential count
- Cytology, immunology, additional tests
For what are CSF samples assessed in terms of their appearance when diagnosing Meningitis ?
Examined for turbidity, coloration and clots.
Healthy is clear and colourless
What is the purpose of a cell count in Meningitis diagnosis ?
Number and type of cells help determine if Meningitis is present and a possible cause.
When does centrifugation of CSF samples occur in Meningitis diagnosis ?
Once cell counts have been determined.
On what samples is centrifugation done in meningitis diagnosis?
Only applies to >0.5ml samples
What is the purpose of sample centrifugation in Meningitis diagnosis?
Used to identify the difference between markedly blood stained and mildly stained samples. This becomes obvious when the supernatant is formed.
What is the importance of sample centrifugation in Meningitis diagnosis?
i. Concentrates the samples
ii. Increases sensitivity Gram stains and culturing meaning you are more likely to isolate the pathogen
If tuberculosis meningitis is suspected, what type of staining is done and why?
b. In tuberculosis meningitis is suspected then acid-alcohol-fast bacilli staining is done at the same time. This is needed because microbacterium tuberculosis have a waxy envelope so don’t adhere to Gram staining.
What happens in culturing of CSF samples in Meningitis diagnosis?
Supernatant inoculated onto Chocolate agar and incubated in Carbon Dioxide for 48 hours.
Why is chocolate agar used for culturing in Meningitis diagnosis?
All potential pathogens that are being isolated grow on Chocolate agar.
What are the 5 potential pathogens that cause Meningitis?
- Haemophilus influenzae
- Neisseria meningitidis
- Streptococcus pneumoniae
- Listeria monocytogenes
- Strep Group B
Why isn’t enrichment broth used in the culturing of samples used to diagnose Meningitis?
Enrichment broth is not advisable because it hardly ever works and there is risk of contamination.
What types of further testing may be done on CSF samples to diagnose Meningitis?
Antigen testing Molecular testing Viral meningitis testing Tuberculosis testing Cryptococcal meningitis testing
When may molecular testing be used to diagnose Meningitis?
Considered optimal for patient management where no causative agent can be found.
Describe the symptoms of viral meningitis.
Symptoms often mild and not diagnosed.
Describe the levels of white cells, glucose and protein in viral meningitis.
Increased white cells, glucose levels are normal but protein levels will be raised.
Which part of the CSF sample can be used for virological analysis to diagnose meningitis?
Supernatant
When may antigen testing be used to diagnose Meningitis?
In cases where neutrophils are high and protein may be high but no bacteria has been isolated.
In some cases of bacterial Meningitis, why is the bacteria often not found?
Bacteria may not have been isolated because patients may have already received antibiotics or early meningitis may mean that insufficient microorganisms are present.
Describe how commercial antigen kits work to diagnose Meningitis and identify bacteria present in a sample
Commercial antigen kits. Antigens against pathogen capsules which are highly antigenic allow agglutination tests against the pathogen to be used. Give a +ve where microscopy and culture are -ve.
What is often used to aid diagnosis of tuberculosis meningitis and why?
PCR is used more often as it provides fast, specific and sensitive results.
In what patients does Cryptococcal meningitis usually occur?
Typically occurs in immunosuppressed patients or patients with cell-mediated immunity defects
How is Cryptococcal meningitis often diagnosed?
- Gram stain of the CSF – presence of typical yeast cells
- Confirmed by india ink preparation
- Antigen tests can also be carried out
How would you expect blood in the CSF to look after a Traumatic lumbar puncture ?
Blood more in initial tubes as compared to later tubes.
Blood clots on standing.
How would you expect blood in the CSF to look after a Subarchnoid haemorrhage?
Blood uniform in all tubes; blood does not clot on standing.
How would you expect supernatant after centrifugation look within 1 hour of collection in the case of a traumatic lumbar puncture ?
Clear
How would you expect supernatant after centrifugation look within 1 hour of collection in the case of a Subarachnoid haemorrhage?
Pink or yellow (Xanthochromia): yellow Xanthochromia develops 12 hours after haemorrhage.
How would you expect a microscopy sample of blood from a CSF sample to look in the case of a traumatic lumbar puncture?
Progressive decrease of red cell counts in later tubes.
How would you expect a microscopy sample of blood from a CSF sample to look in the case of a Subarachnoid haemorrhage ?
Red cell counts uniform in all tubes; haemosiderin-laden macrohages present.
Describe the CSF pressure and CSF protein levels in a traumatic lumbar puncture sample
Both normal
Describe the CSF pressure and CSF protein levels in a Subarachnoid haemorrhage sample.
Both increased
Describe the health and safety requirements when working with N. meningitidis.
All suspected N. meningitidis must be handled in a Class II safety cabinet
What is meant by the term sequelae ?
A condition which is the consequence of a previous disease or injury
What may occur if Meningococcal tissue damage is untreated?
If untreated may become necrotic and amputation may be necessary
What is necrotic tissue and why does it occur?
Having necrotic tissue is a medical condition in which there are dead cells in your body organ. The death of the cells happens due to lack of oxygen and interrupted blood supply
In what type of areas is meningitis likely to have a high prevalence?
- Overcrowding – large number of people in close proximity
o Halls of residence
o Pilgrimage
o Barracks
In what Geographical locations is Meninigits highly prevalent?
o High association of Strep pneumonia with HIV in sub Saharan Africa
o Neisseria meningitidis epidemics common in sub Saharan Africa
o TB meningitis in South East Asia
In what age groups does Meningitis have a high prevalence?
o Neonates particularly susceptible o Toddlers o Young adults o Elderly As well as the immunocompromised and pregnant.
In what people is Neisseria meningitidis common?
Common in very young (<2 years old) and the elderly
How are the different types of Neisseria meningitidis divided?
Divided into serogroups according to polysaccharide outer capsule
In what region are Neisseria meninditidis commensal?
In the upper respiratory tract, specifically the back of the throat
What is peak season for contracting N.meningitidis in the UK?
Jan to March
When does infection with N.meningitidis become life threatening?
When bacteria invade the CSF or blood.
How is N.meningitidis spread in the UK?
Spread among people living in close contact.
What is the major cause of death in terms of Meningococcal disease?
Sepsis
Where are H.influenzae commensal and what is their resevoir?
Commensals of the throat.
Man is resevoir.
How are H.influenzae virulent?
They impede phagocytosis
How is Haemophilus influenzae transmitted?
Droplets
Why are the numbers of viral meningitiis unreliable?
Very few are diagnosed so figures are difficult to obtain. Under-reported because symptoms can be very mild. So the numbers obtained are only from severe cases.
What are the symptoms of Meningitis?
- Vomiting
- Headache
- Lethargy
- Confusion / Altered mental status
- Stiff neck
- Fever
What are the symptoms of Meningococcal Septicaemia?
- Headache
- Neck stiffness
- Photophobia – may be absent but the rash may be extensive
- Bleeding can occur
- May become comatose
When was the MenC vaccine released in the UK?
1999
Who does the MenC vaccine target?
o It was first targeted to everybody up to the age of 18, and to all first year University students.
o This has since extended to include everybody under the age of 25 and people with an increased risk of infection.
How many MenC vaccines are used in the UK?
3
What does MenC vaccine protect against?
- The MenC vaccines only protects against meningococcal diseases caused by serogroup C.
Who is the MenB vaccine offered to?
The MenB vaccine is offered to babies alongside their routine vaccines at 2, 4 and 12 months.
Who is the Men ACWY vaccine offered to ?
Offered to the NHS, teenagers and first-time students
WHat are the clinical compilations of the Haemophilus influenzae vaccination ?
o Hearing loss
o Delayed language
o Mental retardation
o Seizures
