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Micro > Microbiology 1: CNS Infections And Meningitis > Flashcards

Microbiology 1: CNS Infections And Meningitis Flashcards

1
Q

What is the most frequent route of entry for pathogens causing CNS infections ?

A

Haematogenous spread

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2
Q

what is meningitis

A

inflammatory process of the meninges and CSF
neurological damage caused by:
- direct bacterial toxicity
- indirect inflammatory processes and cytokine release
- shock, seizures and cerebral hypoperfusion

can be classified into acute, chronic, aseptic (viral)

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3
Q

List 4 routes of entry to the CNS for pathogens

A
  • Haematogenous spread (meningococcus, pneumococcus)
  • Direct implantation (after surgery)
  • Local extension (from the ear)
  • PNS into CNS (rabies)
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4
Q

Which organism is a common cause of neonatal meningitis ?

A

Group B streptococcus

Floral bacteria in the mothers vagina

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5
Q

What organism commonly causes chronic meningitis ?

A

Tuberculosis

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6
Q

What organisms can cause aseptic meningitis ?

A

Enterovirus - coxsackievirus
Herpes simplex

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7
Q

Which organisms cause acute meningitis ?

A

N.meningitidis
Streptococcus.pneumonia
Haemophilus.influenza

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8
Q

What is aseptic meningitis?

A
  • also known as viral meningitis - no pus found
  • Usually acute viral meningitis
  • not as severe as bacterial
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9
Q

Which N.meningitidis serotypes are there vaccinations for ?

A

B and C

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10
Q

Which virus transferred by vectors including birds and mosquitoes is becoming a leading cause of encephalitis world wide ?

A

West Nile virus

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11
Q

Name a bacterial cause of encephalitis ?

A

Listeria

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12
Q

Which organisms can cause encephalitis via local invasion ?

A

Amoebae (found in warm water)

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13
Q

Which organism causes encephalitis via oral route ? (Eating cat poo 🤮)

A

Toxoplasmosis- e.g toxoplasma gonadii

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14
Q

Most common cause of viral encephalitis in UK

A

Herpes

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15
Q

What are the most common organisms responsible for brain abscesses ?

Why are brain abscesses dangerous?

A
  • Streptococci
  • Staphylococci
  • NB these are common ENT pathogens

Dangerous since cause death due to pressure-related issues

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16
Q

What is the most common route of entry for organisms causing brain abscess ?

Another route?

A

Local extension e.g from mastoiditis or sinusitis

Other route: haematogenously

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17
Q

Name a common spinal infection ?

A

Pyogenic vertebral osteomyelitis

If left untreated, it can lead to permanent neurological deficits, significant spinal deformity, or DEATH

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18
Q

What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?

CSF appearance: clear
Cells: 0-5 leukocytes
Gram stain/antigen tests: negative results
Protein: 0.15-0.4 g/l
Glucose: 2.2-3.3mmol/m

A

Normal

No organisms

**ADD TABLE FROM NOTES PLS**

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19
Q

What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?

CSF appearance: Turbid
Cells: 100-2000 polymorphs
Gram stain/antigen tests: positive results
Protein: 0.5-3.0 g/l
Glucose: 0-2.2 mmol/l

A

Purulent meningitis (bacterial)

Meningococcus
Pneumococcus
Listeria

**ADD TABLE FROM NOTES PLS**

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20
Q

What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?

CSF appearance: clear/slightly turbid
Cells: 15-500 lymphocytes
Gram stain/antigen tests: negative results
Protein: 0.5-1 g/l
Glucose: 2.2-3.3 (normal)

A

Aseptic meningitis

Coxsackie virus
Echovirus
TB

Could also be:
bacterial meningitis partially treated with ABx
Encephalitis
Brain abscess

**ADD TABLE FROM NOTES PLS**

21
Q

What type of meningitis is suggested by this CSF sample ? What are the likely causative organisms ?

CSF appearance: clear/slightly turbid
Cells: 30-500 lymphocytes/ some polymorphs
Gram stain/antigen tests: negative results (scanty acid fast bacilli)
Protein: 1.0-6.0 g/l (high)
Glucose: 0-2.2 (normal)

A

Tuberculous meningitis

Mycobacterium TB

22
Q

Herpes meningitis vs herpes encephalitis

A

Herpes meningitis does NOT need therapy BUT herpes encephalitis is a MEDICAL EMERGENCY

23
Q

Which imaging is best for detecting parenchymal abnormalities e.g. abscesses and infarctions?

Which is more commonly available and so used?

A

Best: MRI

More used: CT

24
Q

Culture and microscopy shows a gram +ve, alpha haemolytic diplococcus organism, what is the likely organism causing the meningitis ?

A

Streptococcus. Pneumoniae

  • this is Gram POSITIVE a-haemolytic diplococcus
  • Gram positive = pneumococcus (diplococci) = Stains purple on gram stain (Positive = Purple)
  • Gram negative = meningococcus = Stains pink on gram stain
25
Q

Culture and microscopy shows a gram -ve diplococci which is non-haemolytic, what organism is the likely cause of this meningitis ?

What would agar show?

A

Meningococcus (Neisseria meningitides) - gram NEGATIVE cocci

  • stains PINK

Agar would show lots of neutrophils

26
Q

Culture and microscopy shows gram +ve purple rods, what organism is the likely cause of this meningitis ?

A

Listeria monocytogenes

27
Q

A 45-year-old presents with headache and neck stiffness over a period of weeks. LP shows cuboidal structures that appear red against a blue stain. What is the causative pathogen?

A

TB

  • NB this happens over WEEKS (chronic meningitis cause)
  • This is Ziehl-Neelsen stain
28
Q

India ink stain: shows orbit structures (yeast cells with surrounding halos)
Lumber puncture: high opening pressure
IN a patient with HIV

What is the likely causative organism of this meningitis ?

A

Cryptococcus Neoformans

29
Q

Which organism commonly causes meningitis in men who have sex with men (MSM)

A

Cryptococcus Neoformans

30
Q

Which drug is effective against Meningococcus, pneumococcus, haemophilus and e.coli ?

A

Ceftriaxone I.V

31
Q

Which drug is effective at treating Listeria ?

A

Amoxicillin

32
Q

Which organism is most commonly associated with recurrent aseptic meningitis (Mollaret’s meningitis) ?

A

HSV-1 and HSV-2

33
Q

Which organisms are the most common cause of aseptic meningitis ?

A

Enterovirus (80%) - Echovirus, coxsackie virus

34
Q

common causes of myelitis

A

poiovirus

35
Q

common causes of neurotoxin release

A

clostridium tenani
clostridium botulinum

36
Q

list other causes of meningitis

A

listeria monocytogenes
group B strep
E. coli

rare:
TB, S. Aureus, T. Pallidum, cryptococcus neoformans

37
Q

describe the processes whereby septicaemia occurs

A
  • capillary leak - albumin and other plasma proteins lead to hypovolaemia
  • coagulopathy - leads to bleeding and thrombosis
  • metabolic derrangeent - acidosis
  • myocardial failure and multi-organ failure
38
Q

complications of TB meningitis

A
  • common in immunosuppressed
  • complications = tuberculosis granulomas
  • tuberculosis abscesses
  • cerebritis
  • there is leptomeningeal enhancement
39
Q

features of aseptic meningitis

A
  • most common infection of the CNS
  • coxsackie group B
  • echoviruses
  • usually in children <1 year
  • self-limiting, resolves in 1-2 weeks
40
Q

how should CSF infections be managed

A
  • within 30 mins - clinical assessment
  • after 1-2 hours - CFS analysis
  • 24-48 hrs - CSF cultures
41
Q

How to clinically differentiate encephalitis from meningitis

A

The disturbance of cognitive function in ecephalitis is what differentiates meningitis to encephalitis

42
Q

Why might you consider doing MRI/CT before LP for CNS infection?

When do you need to do this?

A

Check for raised ICP

ONLY do this if you think there may be raised ICP on clinical suspicion - If you clinically think that the patient does NOT have raised ICP, then you do NOT need to do a CT/MRI before doing an LP (clinical = neuro exam)

43
Q

4 samples to send for Ix if meningitis suspected

A
  • CSF
  • Blood culture
  • Throat swab
  • Sputum culture
44
Q

What colour does gram positive stain?

A

Stains purple on gram stain (Positive= Purple)

  • e.g. Gram positive = pneumococcus (diplococci)
45
Q

What colour does gram negative stain?

A

Stains pink on gram stain e.g. meningicoccus)

46
Q

Which group tend to be infected more by listeria for meningitis? (2)

A
  • Old age (have age-related immunosenescence)
  • Immunosuppressed pts
47
Q

Most common infection of CNS

Which age group does it mainly affect?

How does it resolve?

A

Aseptic Meningitis (viral)

Mainly affects children < 1 year

Self-limiting condition (resolves over 1-2 weeks) - NO antivirals

48
Q

Which group of pts are mainly affected by chronic meningitis + what is common causative organism?

A
  • group: immunosuppressed + old
  • common organism: TB
49
Q

**PLEASE COULD YOU IMAGE OCCLUDE THE TABLE UNDER ‘CLINICAL SYNDROMES’ - JUST OCCLUDE EACH ROW OF SYNDROME (SO 4 BOXES IN TOTAL)**

A

Micro (20 decks)

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