Flashcards in Bacterial and fungal meningitis Deck (30)
What are the features of Neisseria meningitidis?
Gram negative diplococci
Require blood for growth (chocolate agar)
13 capsular types: A, B, C, W135, Y most common
Can also be detected by nucleic acid amplification (PCR)
What are the main differences between the clinical presentations on meningitis and encephalitis?
Focal neurology and confusion absent in meningitis; present in encephalitis.
What is the natural habitat of N. meningitidis?
Nasopharynx - not all strains encapsulated (capsule is a virulence factor)
What factors make N. meningitidis more likely to survive in the bloodstream?
Presence of capsule
Acquisition of iron from ferritin
What are the possible presentations of N. meningitidis infection?
Fulminant septicaemia (no CNS infection)
Septicaemia with purpuric rash (no CNS infection)
Septicaemia with meningitis
Pyogenic (purulent) meningitis with no rash
Chronic meningococcal bacteraemia with arthralgia
What treatment is given can be given for N. meningitidis infection?
Intensive care management
What chemoprophylaxis is given to close contacts of N. meningitidis infection?
What are the features of Haemophilus influenzae?
Small, pleomorphic, Gram negative cocco-bacilli or bacilli
Some strains produce a polysaccharide capsule
Six antigenic types a-f
Type b causes the most invasive disease
Cannot grow in the absence of blood
What is the normal carriage of H. influenzae?
Restricted to humans
25-80% carry non-capsulate strains
5-10% carry capsulate strains
How does H. influenzae reach the bloodstream?
Throat carriage – invasion of submucosa – blood stream
What are the H. influenzae virulence factors?
Type b capsule
Outer membrane proteins/lipolysaccharide
What treatment is given for H. influenzae?
β-lactamase producing strains common
What chemoprophylaxis is given to close contacts of H. influenzae patients?
What are the features of Streptococcus pneumoniae?
Gram positive cocci. Cells in pairs.
Requires blood or serum for growth. α-haemolytic activity on blood
agar (green colour)
Polysaccahride capusle: 95 capsular types
What is the normal habitat of S. pneumoniae?
Human respiratory tract - droplet spread
What treatment is given for S.pneumoniae meningitis?
Penicillin resistant common in some parts of the world
In what group of patients with meningitis should steroids be given?
If S. pneumonia is suspected
Which organisms cause neonatal meningitis?
Group B beta-haemolytic Streptococci
What are the clinical features of neonatal meningitis?
Neonatal infection. Variable onset
Early ( 5 days). Usually meningitis.
What treatment is given for neonatal meningitis?
Ampicillin and gentamicin
What are the complications of meningitis?
- Overwhelming sepsis
- Raised intracranial pressure
- Delayed development
What are the common causes of lymphocytic meningitis?
Virus (HSV etc)
What are the features of TB meningitis?
Epidemiological risk factor for TB:
- AFB often not seen on microscopy
- Delay in diagnosis leads to a worse prognosis
12 months standard TB treatment
What are the features of cryptococcal meningitis?
Cryptococcus is a yeast
Common problem in patients with late stage HIV
Yeast forms seen in CSF in Indian Ink stain
What treatment is given for cryptococcal meningitis?
Prolonged course of treatment with:
- amphotericin, flucytosine or fluconazole
What are the features of Clostridium tetani?
Gram positive spore forming bacillus
Terminal round spore (drumstick)
How does C. tetani produce disease?
- Toxin genes plasmid encoded
- Toxin spreads via bloodstream and retrograde transport
- Binds to ganglioside receptors and blocks release of inhibitory interneurones
- Convulsive contraction of voluntary muscles
What are the clinical features of tetanus?
Tonic muscle spasms
(sympathetic nervous system)
What treatment is given for tetanus?
Antitoxin (horse or human)
Penicillin or metronidazole
Drugs for spasms