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5. CP - Central Nervous System Infections > (26) Bacterial and fungal meningitis > Flashcards

(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
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2
Q

What is meningitis?

A

Infection of the meninges/CSF

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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
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4
Q

What is encephalitis?

A

Infection of the brain tissue

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5
Q

What are the main characteristic of encephalitis?

A
  • acute fever, headache, neck stiffness
  • altered conscious level, seizures +/- focal neurological signs
  • usually viral
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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
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7
Q

What are the rigid containers that encase the brain and spinal cord?

A

Skull and vertebral column

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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

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9
Q

Invasion by microorganisms into brain/spinal cord may occur via…

A

Blood-borne invasion

  • blood-brain barrier
  • blood-CSF barrier

Peripheral nerves

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10
Q

Give 4 different types/causes of meningitis

A
  • bacterial
  • viral
  • TB
  • cryptococcus
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11
Q

What is the cell type found in the different types of meningitis?

A

bacterial = polymorphs

viral = lymphocytes

TB = lymphocytes

cryptococcus = lymphocytes

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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

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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

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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

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15
Q

What type of organism is Neisseria meningitidis?

A

Intracellular, gram-negative, diplococci

may be seen on gram stain in CSF sample

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16
Q

What do Neisseria meningitidis require for growth?

A

Blood (chocolate agar)

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17
Q

There are 13 capsular types of Neisseria meningitidis. Name the most common ones

A
  • A
  • B
  • C
  • W135
  • Y
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18
Q

How else may Neisseria meningitidis be detected?

A

By nucleic acid amplification (PCR)

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19
Q

Where in the body does Neisseria meningitidis have a natural habitat?

A

In the nasopharynx

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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%
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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
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22
Q

Neisseria meningitidis - endotoxin and other cell components leads to what defences?

A
  • host-cell cytokine production

- alternative complement pathway

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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

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24
Q

Can Neisseria meningitidis cross the blood-brain barrier?

A

Crosses the blood-brain endothelium

Multiplication in subarachnoid space

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25
Q

At what age between 0-19 is meningococcal infection most common?

A

Around 6 months

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26
Q

What type of diseases can Neisseria meningitidis cause?

A
  • fulminant septicaemia
  • septicaemia with purpuric rash
  • septicaemia with meningitis
  • pyogenic meningitis with no rash
  • chronic meningococcal bacteraemia with arthralgia
  • focal sepsis
  • conjunctivitis, endophthalmitis
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27
Q

What is the treatment for Neisseria meningitidis?

A
  • ceftriaxone, cefotaxime
  • penicillin
  • early treatment
  • intensive care
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28
Q

How can Neisseria meningitidis infection be prevented?

A

Chemoprophylaxis of contacts of invasive disease

  • rifampicin
  • ciprofloxcin
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29
Q

Which vaccinations are available for Neisseria meningitidis?

A
  • active against group A and C and W135

- no vaccine against group B

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30
Q

Incidence of Neisseria meningitidis fluctuates over time. Where are there peaks?

A
  • winter peaks

- variable serogroup predominance

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31
Q

There can be local outbreaks of Neisseria meningitidis. What do these depend on?

A
  • population of susceptible individuals
  • high transmission rate
  • virulent, capsulate strain
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32
Q

When was the Neisseria meningitidis group C vaccine introduced and what happened as a result?

A

Introduced in November 1999

Marked reduction in group C disease in the UK as a result

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33
Q

What is the African Meningitis belt?

A

Area of sub-Saharan Africa where there is substantial meningococcal disease - massive epidemics

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34
Q

Which strain of Neisseria meningitidis is usually seen in the African meningitis belt?

A

Usually group A

W135 in Burkina Faso

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35
Q

What do haemophilus influenza need to grow?

A

“blood-loving”

Unable to grow in the absence of blood or certain constituents of blood

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36
Q

What was haemophilus influenzae initially thought to be the cause of?

A

Influenza

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37
Q

What type or organism is haemophilus influenzae?

A

Small, pleomorphic Gram-negative cocci-bacilli or bacilli

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38
Q

What do some strains of haemophilus influenzae produce?

A

A polysaccharide capsule

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39
Q

What are the different types of haemophilus influenzae?

A

Six antigenic types a-f

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40
Q

Which type of haemophilus influenzae causes the most invasive disease?

A

Type b

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41
Q

Describe the normal carriage of haemophilus influenzae

A
  • restricted to humans
  • 25-80% carry non-capsulate strain
  • 5-10% carry capsulate strains
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42
Q

What can happen when haemophilus influenzae is carried in the throat?

A
  • invasion of submucosa

- enters blood stream

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43
Q

Describe the invasive infection caused by haemophilus influenzae

A
  • meningitis
  • infants
  • aged 2 months-2 years
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44
Q

What are the virulence factors of haemophilus influenzae?

A
  • type b capsule
  • fimbriae
  • IgA proteases
  • outer membrane proteins/lipopolysaccharide
  • (intercurrent viral infection)
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45
Q

What is the treatment for haemophilus influenzae?

A
  • ceftriaxone, cefotaxime
  • ampicillin
  • B-lactamase producing strains common
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46
Q

What is used as chemoprophylaxis for haemophilus influenzae?

A
  • rifampicin
47
Q

What vaccines exist against haemophilus influenzae?

A

H. influenzae type b conjugate vaccines

  • dramatic reduction in the incidence of invasive disease
48
Q

What type of organism is streptococcus pneumoniae?

A

Gram-positive cocci

Tends to exist in pairs of cells

49
Q

What does streptococcus pneumoniae require for growth?

A

Blood or serum

50
Q

What type of haemolytic activity does strep pneumoniae have on agar and how is this seen?

A

a-haemolytic activity on blood agar - turns it a green colour

51
Q

What type of capsule does strep pneumoniae have and how many capsular types are there?

A

Polysaccharide capsule - 95 capsular types

52
Q

Where is the normal habitat for strep pneumoniae?

A

Human respiratory tract

53
Q

How is strep pneumoniae transmitted?

A

Via droplet spread

54
Q

Why is the Optochin test used?

A

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
Q

Who is affected by strep pneumoniae?

A

All ages

More common and more severe in the elderly

More common in the immunocompromised eg. HIV

56
Q

What is the treatment used for strep pneumoniae?

A
  • ceftriaxone, cefotaxime

- penicillin resistant common in some parts of the world

57
Q

Is there chemoprophylaxis for strep pneumoniae?

A

No chemoprophylaxis of contacts of invasive disease

58
Q

Is there a vaccine for strep pneumoniae?

A

Conjugate vaccine available against common serotypes

59
Q

What happened when the conjugate vaccine for strep pneumonia was introduced in the US?

A

Marked reduction in the incidence of invasive disease in children

60
Q

What were the results of a trial on steroids for meningitis in adults?

A

Meta-analysis of 5 trials, n=623

mortality:

dexamethasone group = 12%
control group = 22%

61
Q

At what time must steroids be given in meningitis?

A

Shortly before or with first dose of antibiotics

62
Q

Describe the dose of steroids used in meningitis

A

Dexamethasone 0.15mg/kg IV every 6 hours x 2-4 days

63
Q

What is a caution when using dexamethasone in meningitis?

A

Dexamethasone decreases vanco levels in the CSF; if vancomycin used, add rifampin

64
Q

In what circumstances may steroids be given for meningitis?

A

If S. pneumoniae is suspected

No evidence of benefit in meningococcal meningitis

65
Q

What is neonatal meningitis normally caused by?

A
  • group B beta-haemolytic streptococci
  • escherichia coli
  • listeria monocytogenes
66
Q

How is the onset of neonatal meningitis classified?

A
  • early (5 days old) - usually meningitis
67
Q

How is neonatal meningitis treated?

A
  • cefotaxime

- ampicillin and gentamicin

68
Q

What are the complications of meningitis?

A
  • death
  • overwhelming sepsis
  • raised intracranial pressure
  • longer term problems
  • deafness
  • delayed development
  • seizures
  • stroke
  • hydrocephalus
69
Q

Give 3 different types of lymphocytic meningitis

A
  • viral meningitis
  • spirochete meningitis
  • TB meningitis
70
Q

State the characteristics of viral meningitis

A
  • most common form of meningitis
  • enteroviruses
  • herpes simplex
  • benign outcome
  • symptomatic treatment
71
Q

Which spirochete bacteria can cause meningitis?

A
  • treponemal

- borrelia

72
Q

Can polio cause meningitis?

A

Polio virus can cause meningitis that may lead to paralysis

This is prevented by vaccination

73
Q

State the characteristic of TB meningitis?

A
  • important differential
  • insidious onset
  • epidemiological risk factors for TB = immunocompromised, alcoholic, comes from endemic area
74
Q

Why is diagnosis of TB meningitis difficult?

A
  • AFB often not seen on microscopy

- delay in diagnosis leads to a worse prognosis

75
Q

How is TB meningitis treated?

A
  • 12 months standard TB treatment

- steroids beneficial

76
Q

How is TB directly detected?

A
  • Ziehl-Neelsen stain

- fluorescent antibody stain

77
Q

What is the cause of brain abscess?

A

Usually bacterial

78
Q

How are bacteria spread to cause brain abscess?

A
  • spread of organisms from adjacent structures eg. middle ear, sinuses e.g.. step. anaerobes
  • blood stream spread eg. staph. aureus
79
Q

How would you confirm a diagnosis of brain abscess?

A

Brain imaging

80
Q

How would you treat brain abscess?

A

Prolonged course of antibiotic therapy

81
Q

What type of organisms is cryptococcus?

A

A yeast

82
Q

Cryptococcal meningitis is a problem seen in who?

A

Patients with late stage HIV - insidious onset

83
Q

What type of meningitis is cryptococcal meningitis?

A

Lymphocytic meningitis

84
Q

What stain is used to see cryptococcus in cryptococcal meningitis?

A

Yeast forms seen in CSF in Indian ink stanin

85
Q

What treatment is used for cryptococcal meningitis?

A

Prolonged course of treatment with

  • amphotericin
  • flucytosine
  • fluconazole
86
Q

What is the usual cause of encephalitis?

A

Usually viral

In the UK, herpes simplex is most common

87
Q

What are the characteristic of encephalitis?

A
  • involvement of the brain tissue

- altered conscious level

88
Q

What part of the brain does encephalitis usually affect?

A

Preferentially affects the temporal lobes

89
Q

At what age does encephalitis occur?

A

Occurs at all ages

50% in the over 50s

90
Q

How is encephalitis diagnosed?

A

By detecting viral nucleic acid in CSF (PCR)

91
Q

What may encephalitis cause long-term?

A

May cause severe long term neurological problems

92
Q

HSV is the most common cause of encephalitis in the UK but what is the most common cause worldwide?

A

Japanese encephalitis virus (an arbovirus)

93
Q

Japanese encephalitis most commonly affects who?

A

Children

94
Q

What is the prognosis in Japanese encephalitis?

A
  • one third die in the acute illness
  • one third left with severe long term neurological disability
  • one third recover
95
Q

Is Japanese encephalitis preventable?

A

Preventable by vaccination

96
Q

How is rabies encephalitis caused?

A

Dog, fox, bat bites

Common still in many countries

97
Q

What is the prognosis in rabies encephalitis?

A

100% mortality

98
Q

Is rabies encephalitis preventable?

A

Preventable by vaccination

99
Q

What type of organism is clostridium tetani?

A
  • gram-positive spore forming bacillus
  • terminal round spore (drumstick)
  • strict anaerobe
100
Q

Where is clostridium tetani found and how can it infect?

A

Widespread in the soil

  • implantation of contaminated soil into a wound
  • wound may be major or minor
101
Q

Which toxin does clostridium tetani produce?

A

Clostridium tetani is non-invasive but produces tetanospasmin

102
Q

Describe the mechanism of action of tetanospasmin (clostridium tetani)

A
  • 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
Q

What are the symptoms of tetanus (lock jaw)?

A
  • tonic muscle spasms
  • trismus
  • opisthotonus
  • respiratory difficulties
  • cardiovascular instability
  • (sympathetic nervous system)
104
Q

What is trismus? (symptom of tetanus)

A

Spasm of the jaw muscles, causing the mouth to remain tightly closed

105
Q

What does tonic muscle spasms mean? (symptom of tetanus)

A

Continued muscular contraction as opposed to a series of alternating muscular contractions and relaxations (clonic spasm

106
Q

What is opisthotonus? (symptom of tetanus)

A

State of severe hyperextension and spasticity in which the head, neck and spinal column enter into a complete “bridging” or “arching” position

107
Q

What is the most common entry site of clostridium tetani?

A

Foot (41.5%)

108
Q

The foot is the most common entry site of clostridium tetani. What are the other entry sites?

A
  • leg (8.9%)
  • hand (8.3%)
  • head/neck (8.2%)
  • other (11.2%)
  • unknown (21.9%)
109
Q

What is the treatment for clostridium tetani?

A
  • antitoxin (horse or human)
  • penicillin or metronidazole
  • drugs for spasms
  • muscle relaxants
  • respiratory supports
110
Q

What is given to prevent clostridium tetani infection?

A

Toxoid

111
Q

How has the epidemiology of tetanus changed in the UK over the past 100 years?

A

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
Q

At what ages do most tetanus cases occur?

A

65+ years (more in females)

Increased in number of reports as age increases

113
Q

How many cases and how many deaths from tetanus are there each year worldwide?

A

1 million require hospital treatment each year

400,00 deaths

5. CP - Central Nervous System Infections (3 decks)

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