(26) Bacterial and fungal meningitis Flashcards
1
Q
Give 4 types of CNS infections
A
- meningitis
- encephalitis
- brain abscesses
- toxin mediated CNS infections eg. tetanus
2
Q
What is meningitis?
A
Infection of the meninges/CSF
3
Q
What are the main characteristics of meningitis?
A
- actue fever, headache, neck stiffness, +/- rash
- fully conscious, no focal neurological signs
- usually viral by may be bacterial
4
Q
What is encephalitis?
A
Infection of the brain tissue
5
Q
What are the main characteristic of encephalitis?
A
- acute fever, headache, neck stiffness
- altered conscious level, seizures +/- focal neurological signs
- usually viral
6
Q
What are the main features of brain abscesses?
A
- insidious onset of fever, headache, +/- neck stiffness
- +/- altered conscious level, seizures, focal neurological signs
- usually bacterial, may be parasitic
7
Q
What are the rigid containers that encase the brain and spinal cord?
A
Skull and vertebral column
8
Q
How do the skull and vertebral column protect the brain and spinal cord?
A
Protect against mechanical pressure and also the spread of infection
9
Q
Invasion by microorganisms into brain/spinal cord may occur via…
A
Blood-borne invasion
- blood-brain barrier
- blood-CSF barrier
Peripheral nerves
10
Q
Give 4 different types/causes of meningitis
A
- bacterial
- viral
- TB
- cryptococcus
11
Q
What is the cell type found in the different types of meningitis?
A
bacterial = polymorphs
viral = lymphocytes
TB = lymphocytes
cryptococcus = lymphocytes
12
Q
What is the cell count in different types of meningitis?
A
Normal = less than 5
bacterial = over 200
viral = 20-200
TB = 20-200
cryptococcus = 20-200
13
Q
What is the glucose level in different types of meningitis?
A
normal = 2.5-4.0 mmol/L
bacterial = less than 2.0 mmol/L
viral = normal or reduced
TB = reduced
cryptococcus = normal or reduced
14
Q
What is the protein level in different types of meningitis?
A
normal = 0.15-0.4 g/L
bacterial = increased
viral = normal or increased
tb = increased
cryptococcus = increased
15
Q
What type of organism is Neisseria meningitidis?
A
Intracellular, gram-negative, diplococci
may be seen on gram stain in CSF sample
16
Q
What do Neisseria meningitidis require for growth?
A
Blood (chocolate agar)
17
Q
There are 13 capsular types of Neisseria meningitidis. Name the most common ones
A
- A
- B
- C
- W135
- Y
18
Q
How else may Neisseria meningitidis be detected?
A
By nucleic acid amplification (PCR)
19
Q
Where in the body does Neisseria meningitidis have a natural habitat?
A
In the nasopharynx
20
Q
Can you be a carrier of Neisseria meningitidis?
A
- 5-20% carriers (increased in smokers)
- half carried strains non-capsulate
- in outbreak communities carriage 20-90%
21
Q
What are the factors that affect intravascular survival of Neisseria meningitidis?
A
- capsule (protects against complement-mediated bacteriolysis and phagocytosis)
- acquisition of iron from transferrin
22
Q
Neisseria meningitidis - endotoxin and other cell components leads to what defences?
A
- host-cell cytokine production
- alternative complement pathway
23
Q
Neisseria meningitidis - endotoxin and other cell components leads to host cell cytokine production. Which cytokines?
A
Inflammatory cytokines
- TNFa
- IL-1b
- IL-6
- IL-8
Anti-inflammatory cytokines
- IL-10
24
Q
Can Neisseria meningitidis cross the blood-brain barrier?
A
Crosses the blood-brain endothelium
Multiplication in subarachnoid space
25
At what age between 0-19 is meningococcal infection most common?
Around 6 months
26
What type of diseases can Neisseria meningitidis cause?
- fulminant septicaemia
- septicaemia with purpuric rash
- septicaemia with meningitis
- pyogenic meningitis with no rash
- chronic meningococcal bacteraemia with arthralgia
- focal sepsis
- conjunctivitis, endophthalmitis
27
What is the treatment for Neisseria meningitidis?
- ceftriaxone, cefotaxime
- penicillin
- early treatment
- intensive care
28
How can Neisseria meningitidis infection be prevented?
Chemoprophylaxis of contacts of invasive disease
- rifampicin
- ciprofloxcin
29
Which vaccinations are available for Neisseria meningitidis?
- active against group A and C and W135
| - no vaccine against group B
30
Incidence of Neisseria meningitidis fluctuates over time. Where are there peaks?
- winter peaks
| - variable serogroup predominance
31
There can be local outbreaks of Neisseria meningitidis. What do these depend on?
- population of susceptible individuals
- high transmission rate
- virulent, capsulate strain
32
When was the Neisseria meningitidis group C vaccine introduced and what happened as a result?
Introduced in November 1999
Marked reduction in group C disease in the UK as a result
33
What is the African Meningitis belt?
Area of sub-Saharan Africa where there is substantial meningococcal disease - massive epidemics
34
Which strain of Neisseria meningitidis is usually seen in the African meningitis belt?
Usually group A
W135 in Burkina Faso
35
What do haemophilus influenza need to grow?
"blood-loving"
Unable to grow in the absence of blood or certain constituents of blood
36
What was haemophilus influenzae initially thought to be the cause of?
Influenza
37
What type or organism is haemophilus influenzae?
Small, pleomorphic Gram-negative cocci-bacilli or bacilli
38
What do some strains of haemophilus influenzae produce?
A polysaccharide capsule
39
What are the different types of haemophilus influenzae?
Six antigenic types a-f
40
Which type of haemophilus influenzae causes the most invasive disease?
Type b
41
Describe the normal carriage of haemophilus influenzae
- restricted to humans
- 25-80% carry non-capsulate strain
- 5-10% carry capsulate strains
42
What can happen when haemophilus influenzae is carried in the throat?
- invasion of submucosa
| - enters blood stream
43
Describe the invasive infection caused by haemophilus influenzae
- meningitis
- infants
- aged 2 months-2 years
44
What are the virulence factors of haemophilus influenzae?
- type b capsule
- fimbriae
- IgA proteases
- outer membrane proteins/lipopolysaccharide
- (intercurrent viral infection)
45
What is the treatment for haemophilus influenzae?
- ceftriaxone, cefotaxime
- ampicillin
- B-lactamase producing strains common
46
What is used as chemoprophylaxis for haemophilus influenzae?
- rifampicin
47
What vaccines exist against haemophilus influenzae?
H. influenzae type b conjugate vaccines
- dramatic reduction in the incidence of invasive disease
48
What type of organism is streptococcus pneumoniae?
Gram-positive cocci
Tends to exist in pairs of cells
49
What does streptococcus pneumoniae require for growth?
Blood or serum
50
What type of haemolytic activity does strep pneumoniae have on agar and how is this seen?
a-haemolytic activity on blood agar - turns it a green colour
51
What type of capsule does strep pneumoniae have and how many capsular types are there?
Polysaccharide capsule - 95 capsular types
52
Where is the normal habitat for strep pneumoniae?
Human respiratory tract
53
How is strep pneumoniae transmitted?
Via droplet spread
54
Why is the Optochin test used?
Optochin (or ethylhydrocupreine) is a chemical used for the identification of Streptococcus pneumoniae, which is optochin-sensitive, from other alpha-hemolytic streptococci such as Streptococcus viridans, which are resistant
55
Who is affected by strep pneumoniae?
All ages
More common and more severe in the elderly
More common in the immunocompromised eg. HIV
56
What is the treatment used for strep pneumoniae?
- ceftriaxone, cefotaxime
| - penicillin resistant common in some parts of the world
57
Is there chemoprophylaxis for strep pneumoniae?
No chemoprophylaxis of contacts of invasive disease
58
Is there a vaccine for strep pneumoniae?
Conjugate vaccine available against common serotypes
59
What happened when the conjugate vaccine for strep pneumonia was introduced in the US?
Marked reduction in the incidence of invasive disease in children
60
What were the results of a trial on steroids for meningitis in adults?
Meta-analysis of 5 trials, n=623
mortality:
dexamethasone group = 12%
control group = 22%
61
At what time must steroids be given in meningitis?
Shortly before or with first dose of antibiotics
62
Describe the dose of steroids used in meningitis
Dexamethasone 0.15mg/kg IV every 6 hours x 2-4 days
63
What is a caution when using dexamethasone in meningitis?
Dexamethasone decreases vanco levels in the CSF; if vancomycin used, add rifampin
64
In what circumstances may steroids be given for meningitis?
If S. pneumoniae is suspected
No evidence of benefit in meningococcal meningitis
65
What is neonatal meningitis normally caused by?
- group B beta-haemolytic streptococci
- escherichia coli
- listeria monocytogenes
66
How is the onset of neonatal meningitis classified?
- early (5 days old) - usually meningitis
67
How is neonatal meningitis treated?
- cefotaxime
| - ampicillin and gentamicin
68
What are the complications of meningitis?
- death
- overwhelming sepsis
- raised intracranial pressure
- longer term problems
- deafness
- delayed development
- seizures
- stroke
- hydrocephalus
69
Give 3 different types of lymphocytic meningitis
- viral meningitis
- spirochete meningitis
- TB meningitis
70
State the characteristics of viral meningitis
- most common form of meningitis
- enteroviruses
- herpes simplex
- benign outcome
- symptomatic treatment
71
Which spirochete bacteria can cause meningitis?
- treponemal
| - borrelia
72
Can polio cause meningitis?
Polio virus can cause meningitis that may lead to paralysis
This is prevented by vaccination
73
State the characteristic of TB meningitis?
- important differential
- insidious onset
- epidemiological risk factors for TB = immunocompromised, alcoholic, comes from endemic area
74
Why is diagnosis of TB meningitis difficult?
- AFB often not seen on microscopy
| - delay in diagnosis leads to a worse prognosis
75
How is TB meningitis treated?
- 12 months standard TB treatment
| - steroids beneficial
76
How is TB directly detected?
- Ziehl-Neelsen stain
| - fluorescent antibody stain
77
What is the cause of brain abscess?
Usually bacterial
78
How are bacteria spread to cause brain abscess?
- spread of organisms from adjacent structures eg. middle ear, sinuses e.g.. step. anaerobes
- blood stream spread eg. staph. aureus
79
How would you confirm a diagnosis of brain abscess?
Brain imaging
80
How would you treat brain abscess?
Prolonged course of antibiotic therapy
81
What type of organisms is cryptococcus?
A yeast
82
Cryptococcal meningitis is a problem seen in who?
Patients with late stage HIV - insidious onset
83
What type of meningitis is cryptococcal meningitis?
Lymphocytic meningitis
84
What stain is used to see cryptococcus in cryptococcal meningitis?
Yeast forms seen in CSF in Indian ink stanin
85
What treatment is used for cryptococcal meningitis?
Prolonged course of treatment with
- amphotericin
- flucytosine
- fluconazole
86
What is the usual cause of encephalitis?
Usually viral
In the UK, herpes simplex is most common
87
What are the characteristic of encephalitis?
- involvement of the brain tissue
| - altered conscious level
88
What part of the brain does encephalitis usually affect?
Preferentially affects the temporal lobes
89
At what age does encephalitis occur?
Occurs at all ages
50% in the over 50s
90
How is encephalitis diagnosed?
By detecting viral nucleic acid in CSF (PCR)
91
What may encephalitis cause long-term?
May cause severe long term neurological problems
92
HSV is the most common cause of encephalitis in the UK but what is the most common cause worldwide?
Japanese encephalitis virus (an arbovirus)
93
Japanese encephalitis most commonly affects who?
Children
94
What is the prognosis in Japanese encephalitis?
- one third die in the acute illness
- one third left with severe long term neurological disability
- one third recover
95
Is Japanese encephalitis preventable?
Preventable by vaccination
96
How is rabies encephalitis caused?
Dog, fox, bat bites
Common still in many countries
97
What is the prognosis in rabies encephalitis?
100% mortality
98
Is rabies encephalitis preventable?
Preventable by vaccination
99
What type of organism is clostridium tetani?
- gram-positive spore forming bacillus
- terminal round spore (drumstick)
- strict anaerobe
100
Where is clostridium tetani found and how can it infect?
Widespread in the soil
- implantation of contaminated soil into a wound
- wound may be major or minor
101
Which toxin does clostridium tetani produce?
Clostridium tetani is non-invasive but produces tetanospasmin
102
Describe the mechanism of action of tetanospasmin (clostridium tetani)
- toxin genes are encoded in plasmid
- toxin spreads via bloodstream ad retrograde transport
- binds to ganglioside receptors and blocks release of inhibitory interneurones
- convulsive contraction of voluntary muscles
103
What are the symptoms of tetanus (lock jaw)?
- tonic muscle spasms
- trismus
- opisthotonus
- respiratory difficulties
- cardiovascular instability
- (sympathetic nervous system)
104
What is trismus? (symptom of tetanus)
Spasm of the jaw muscles, causing the mouth to remain tightly closed
105
What does tonic muscle spasms mean? (symptom of tetanus)
Continued muscular contraction as opposed to a series of alternating muscular contractions and relaxations (clonic spasm
106
What is opisthotonus? (symptom of tetanus)
State of severe hyperextension and spasticity in which the head, neck and spinal column enter into a complete "bridging" or "arching" position
107
What is the most common entry site of clostridium tetani?
Foot (41.5%)
108
The foot is the most common entry site of clostridium tetani. What are the other entry sites?
- leg (8.9%)
- hand (8.3%)
- head/neck (8.2%)
- other (11.2%)
- unknown (21.9%)
109
What is the treatment for clostridium tetani?
- antitoxin (horse or human)
- penicillin or metronidazole
- drugs for spasms
- muscle relaxants
- respiratory supports
110
What is given to prevent clostridium tetani infection?
Toxoid
111
How has the epidemiology of tetanus changed in the UK over the past 100 years?
Increasing since 1918 with peak at around 1925
Production of first toxoid in 1924 causing a decreased after the peak
Extensive military use during WWII
Routine childhood immunisation in late 1940s
Rates very low since 1960S
112
At what ages do most tetanus cases occur?
65+ years (more in females)
Increased in number of reports as age increases
113
How many cases and how many deaths from tetanus are there each year worldwide?
1 million require hospital treatment each year
400,00 deaths
