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Microbiology > CNS Infections > Flashcards

CNS Infections Flashcards

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1
Q

What is special about CNS infections?

A
  • Mode of presentation varies widely•
  • Life-threatening diseases•
  • Time to presentation & speed of progression varies widely•
  • Prompt diagnosis with appropriate therapy is essential.
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2
Q

What are the 4 routes of entry into CNS?

A

a) haematogenous spread

b) direct implantation - via instrumentation

c) local extension - secondary to established infections

  • otitis externa/media
  • mastoiditis

d) PNS into CNS

  • rabies
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3
Q

What is the most frequent route of entry in CNS infection?

A

Haematogenous spread

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4
Q

What are the CNS clinical syndromes. What region do they affect? What are the sign and symptoms? What are the causative agents?

A
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5
Q

Define meningitis

A

inflammatory process of meninges and CSF

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6
Q

Define meningoencephalitis.

A

inflammation of meninges and brain parenchyma

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7
Q

How does meningitis cause neurological damage? What is the mortality and morbidity?

A

Neurological damage by:

  • •Direct bacterial toxicity.•
  • Indirect inflammatory process and cytokine release and oedema.•
  • Shock, seizures, and cerebral hypoperfusion.

Mortality ~ 10%

Morbidity ~ 5%

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8
Q

How do we classify meningitis?

A
  • Acute - usually bacterial meningitis - hours
  • Chronic - usually TB, spirochetes, cryptococcus - months
  • Aseptic - usually acute viral
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9
Q

Which classification would meningococcal meningitis be?

A

Acute

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10
Q

What are the clinical features of meningitis?

A
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11
Q

What are the causes of acute meningitis?

A

First 3 - most common

Second 3 - less common

Listeria - important in pregnancy and immunocompromise

GBS - vaginal colonisation

E.coli - in the gut. Important in neonatal population

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12
Q

Describe N.meningitides.

A
  • Infectious cause of childhood death in all countries.•
  • Transmission is person-to-person, from asymptomatic carriers.•
  • Pathogenic strains are found in only 1% of carriers.•
  • Cause infections in less than 10 days.

Meningococcus drops platelet count therefore non blanching rash.

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13
Q

Apart from meningitis, what can N.meningitides cause?

A

The clinical difference between septicemia and meningitis is important because patients who present with shock are treated differently than patients who present primarily with increased intracranial pressure (ICP).

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14
Q

What is the clinical presentation of septicaemia?

A
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15
Q

Describe.

A

CT scan - tuberculous meningitis –

enhancement in the basal cistern and

meninges, with dilatation

of the ventricles.

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16
Q

Describe Chronic Tuberculoud meningitis

A

Incidence: 544 per 100,000 population in Africa.

More common in patients who are immunosuppressed.

Mortality was 5.5 deaths per 100,000 persons.

Involves the meninges and basal cisterns of the brain and spinal cord.

Can result in tuberculous granulomas, tuberculous abscesses, or cerebritis

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17
Q

Describe.

A

Tuberculous abscess in the left

parietal region. Note the enhancing

thick-walled abscess.

18
Q

Describe aseptic meningitis.

A

Aseptic meningitis is the most common infection of the CNS.

Patients with aseptic meningitis have headache, stiff neck, and photophobia.

A nonspecific rash can accompany these symptoms.

Enteroviruses (e.g. Coxsackievirus group B and echoviruses) are responsible for 80-90% cases in which a causative organism of aseptic meningitis is identified.

It most frequently occurs in children younger than 1 year.

The clinical course of aseptic meningitis is self-limited and resolves in 1-2 weeks

19
Q

What are the viral causes of CNS infections? What age groups do they affect? When do they occur?

A
20
Q

What is the most common cause of encephalitis?

A

VIRUSES

21
Q

What is the most common transmission in encephalitis?

A

Transmission is commonly either person to person, or through vectors:

Mosquitoes

Lice

Ticks

Various viridae from Togavirus, Flavivirus, and Bunyavirus families.

But, West Nile Virus is becoming a leading cause of encephalitis internationally…..

22
Q

What are other infectious causes of encephalitis?

A

Bacterial encephalitis

•Listeria monocytogenes - blue cheese and mayo

Amoebic encephalitis

  • •Naegleria fowleri•
  • Habitat – warm water•
  • Acanthamoeba species, and Balamuthiamandrillaris,
  • brain abscess, aseptic or chronic meningitis.

Toxoplasmosis

  • An obligate intracellular protozoal parasite, Toxoplasma gondii.•
  • Via the oral, transplacental route or organ transplantation.•
  • Severe infection in immunocompromised patients.
  • •Affected organs include the gray and

white matter of the brain, retinas,

alveolar lining of the lungs, heart,

and skeletal muscle.

23
Q

Describe the picture

A

Brain abscess

24
Q

What is the most common route of infection in brain abscesses?

A

Local invasion: otitis media/mastoiditis/paranasal sinuses endocarditis/haematogenously

25
Q

What causes brain abscesses?

A
  • Streptococci* (both aerobic and anaerobic)
  • Staphylococci*,

Gram-negative organisms. (particularly in neonates)

Mycobacterium tuberculosis

fungi

parasites

Actinomyces and Nocardia species

26
Q

Describe spinal infections.

A

Pyogenic vertebral osteomyelitis common form of vertebral infection.

Direct open spinal trauma, from infections in adjacent structures, from hematogenous spread of bacteria to a vertebra.

Left untreated, it can lead to permanent neurologic deficits, significant spinal deformity, or death.

27
Q

What are the RFs of spinal infections?

A
  • Advanced age
  • Intravenous drug use
  • Long-term systemic steroids
  • Diabetes mellitus
  • Organ transplantation
  • Malnutrition
  • Cancer
28
Q

What Ix do we use for CNS infections?

A
  • MRI is superior to CT scanning in detecting parenchymal abnormalities such as abscesses and infarctions.•
  • Central nervous system infections:
  • CSF sample
  • brain tissue
29
Q

Describe the CSF studies?

A
30
Q

In addition to CSF, what microbiological investigations would you do?

A

Blood culture,

Throat swab

Blood PCR

31
Q

Fill out.

A
32
Q
A

Purple = Gram +ve

Pink = Gram -ve

Cocci - spherical

Rod - Cuboidal

Gram positive cocci- pneumococcus

33
Q
A

Gram negative cocci- meningococcus

34
Q
A

Gram positive rod- Listeria

older immunocompromised

35
Q
A

Ziehl-Neelsen stain- TB

36
Q
A

Immunocompromised, high pressure chronic meningitis.

Indian ink stains- cryptococcus

37
Q

What are the limitations of diagnostics

A

MRI oedema pattern and moderate mass effect cannot be differentiated from tumor or stroke or vasculitis in some patients.

Infections in early stages and serological tests.

Amount of CSF.

PCR techniques.

Methods to detect amoebic infections.

Availability of good laboratory technique.

38
Q

How do you approach pt with possible CNS infections

A

Abx immediately.

39
Q

What is the generic therapy

A
40
Q

What adjunctive therapy is used in CNS infections?

A
  • Level of care•
  • Corticosteroids•
  • ? Repeat lumbar puncture•
  • Public health

Microbiology (19 decks)

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