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MICBI - Clinical MICBI > L37 Bacterial infection of CNS > Flashcards

L37 Bacterial infection of CNS Flashcards

1
Q

Acute vs Chronic meningitis?

A

Acute: meningeal symptoms from few hours to few days;

Chronic: over weeks, CSF remains abnormal for >4 weeks

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2
Q

What is the dural venous sinus?

A

It is where the periosteal and meningeal layers separate

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3
Q

CSF is produced at the choroid plexus in the ventricles > flow?

A
  1. To the 3rd ventricle > 4th ventricle through cerebral aqueduct
  2. Flows into subarachnoid space by the lateral and medial apertures + spinal canal
  3. CSF removes waste and provide buoyancy from within the subarachnoid space
  4. Excess CSF will be absorbed by arachnoid villi > drained to superior sagittal sinus
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4
Q

Clinical presentations of acute bacterial meningitis can be non- specific, e.g. acute onset of fever and headache.

What are the signs of meningeal irritation? (4)

A
  1. Nuchal rigidity: neck stiffness, inability to flex the neck
  2. Kernig’s sign: when thigh is flexed and knee at 90 degrees, subsequent extension of knee is painful
  3. Brudzinski’s sign: when patient lies supine, lifting the patient’s head off the couch causes lifting of legs involuntarily
  4. Jolt accentuation of headache: increase headache when head is turned horizontally 2-3 times
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5
Q

List some examples of the below manifestations in acute bacterial meningitis

  1. Eye effects
  2. Mental alteration
  3. Hemorrhage
  4. Raised ICP
A
  1. Photophobia, diplopia
  2. Confusion, coma
  3. Petechiae, ecchymosis
    • Early: headache, vomiting, papilloedema
    • Late: CN3,6 palsies, hemiparesis
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6
Q

What are the signs of raised ICP in neonates? (3)

A
  • Bulging fontanelle
  • Enlarged cranium
  • Seizures
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7
Q

What are the general risk factors for acute bacterial meningitis?

A
  1. Immunocompromised: complement deficiency, splenectomy, HIV
  2. NPC - post-radiotherapy may lead to deformities of the bone > prone to invasive strep pneumoniae infection
  3. Skull base fracture
  4. Otitis media
  5. Cranial trauma, CSF shunts (placement of CSF shunt systems to treat hydrocephalus before)
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8
Q

What are the most common organisms causing bacterial meningitis in neonates (infants <3m)? (3)

A

MC:
Group B strep >
E.coli >
Listeria monocytogenes

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9
Q

What are the specific risk factors for neonatal bacterial meningitis? (3)

A
  1. Maternal GBS colonisation
  2. Prematurity
  3. Prolonged rupture of membrane during labor
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10
Q

How can neonatal meningitis be prevented?

A
  1. Screening at 35-37 weeks for GBS

2. Intrapartum antibiotic prophylaxis (penicillin/ampicillin)

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11
Q

What are the MC organisms for bacterial meningitis in children >3m?

A

similar to adults (5)

+ Haemophilis influenzae

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12
Q

What are the MC organisms for bacterial meningitis in adults? (5)

A
  1. Strep pneumoniae
  2. N. meningitidis
  3. Strep suis
  4. Listeria monocytogenes
  5. M. tuberculosis
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13
Q

What are the specific risk factor(s) for bacterial meningitis in

a) children >3m
b) adults?

A

a) pre-existing acute otitis media

b) Debilitated (weak), Elderly, Diabetic

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14
Q

What can be done to prevent bacterial meningitis in children >3m? (4)

A

Vaccination x4

  1. PCV 13
    - Pneumococcal conjugate vacine
  2. Hib vaccine
  3. Meningococcal group C+ Y
  4. BCG (in children immunisation programme)
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15
Q

What can be done to prevent bacterial meningitis in adults? (3)

A
  1. PCV13 + booster PPSV23 (Pneumococcal polysaccharide vaccine)
  2. Meningococcal A/C/W/Y-135 (for travellers to endemic areas)
  3. Meningococcal group B (teenagers)
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16
Q

Procedure-related meningitis/ Intra-cranial shunts can be causes for meningitis.
What are the usual organisms? (2)

Prevention is by infection control

A
  1. S.aureus/ MRSA

2. GN rods

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17
Q

Prophylaxis for pneumococcal meningitis?

A

PCV13/
PPSV23
vaccine

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18
Q

Streptococcus pneumoniae can be commonly found in which organ?

It causes the highest morality of meningitis (20%), can causes cerebral edema, CN palsy etc.

What is the treatment ?

A

Nasopharynx

  1. IV Cefotaxime as empirical treatment until organisms sensitivity is available >

depending on resistance, IV penicillin G > IV cefotaxime > IV vancomycin + rifampicin

  1. Dexamethasone -.15mg/kg, IV Q6h x4/7 may reduce mortality and hearing loss
19
Q

Neisseria meningitidis can be normally found at?

What are the commonest presentations in patients infected?

A

Nasopharynx

  • Petechiae, purpura 50%
20
Q

Neisseria meningitides can have a rapid progression , and may even cause Waterhouse-Friderichsen syndrome. What is that?

Treatment?

A

Waterhouse-Friderichsen syndrome - shock, DIC, bilateral adrenal hemorrhage

> adrenocortical insuffciency

Treatment: Cefotaxime

21
Q

What are the preventive measures for meningococcal meningitis?

A
  1. Group A/C/Y/W-135 vaccine
  2. Group B vaccine
  3. Rifampicin for close contacts, not necessary for medical personnel
22
Q

Which organism infect infants from 1 month to 3 years old most?

What serotype is the most virulent?

It causes cerebral oedema, hydrocephalus, CN palsy (e.g. deafness)

How to prevent?

A

Haemophilus influenzae; Type B

Hib vaccine, rifampicin for close contacts

*Cefotaxime is given for treatment, ampicillin if sensitive

23
Q

Which organism causing meningitis is found in pigs thus butchers, and associated with high incidence of deafness?

Treatment?

A

Streptococcus suis
(Group D strep)

High dose benzylpenicillin 14-21 days

24
Q

List the 4 routes of entry of bacterial meningitis.

A
  1. Hematogenous spread (MC)
    e. g. nasopharyngeal epithelium
  2. Direct contiguous spread
    - e.g AOM, sinusitis
  3. Direct inoculation
    - e.g. open skull fracture
  4. Vertical transmission
25
Q

Causative organisms invade the meninges via various BBB receptors, and replicate in the ________________due to local immunodeficiency. Then there is immune system activation and cytokine production.
What are the effects? (3)

A

subarachnoid space

  1. Increase BBB permeability > vasogenic edema > increase CSF outflow resistance > hydrocephalus > interstitial edema
  2. Increase ROS by bacterial toxin > cytotoxic edema
  3. Altered cerebral blood flow (CBF), reduced perfusion pressure, ischemia

ALL = Increase intracranial pressure - cerebral ischemia, brain herniation

26
Q

What initial investigations to be done in suspected meningitis? (5)

A
  1. CT to rule out any mass lesion before LP
    - if mass is present in brain/ elevated ICP, LP may lead to brain herniation
  2. CSF for microbiological investigations; by lumbar puncture
  3. Plasma glucose
  4. Blood culture
  5. Serology for viral studies: throat swab, stool culture
27
Q

If there is increased opening pressure (normal 10-20cm H2O) in CSF puncture, it suggested?

A

increased ICP from cerebral edema

28
Q

What microbiological tests to be done in CSF sample?

A
  1. Gram stain (H.influenzae)
  2. ZN stain and rapid DNA detection for TB
  3. India ink for Cryptococcus
  4. Bacterial culture
  5. Latex agglutination for bacterial + Cryptococcus antigens
29
Q

What is the typical CSF interpretation in bacterial meningitis? (5)

A
  1. Cloudy appearance
  2. Increase in WBC per ul
  3. Polymorphs as predominant cells (>80%) compared to lymphocytes
  4. Reduced glucose, <2.2 (due to increase consumption + reduced glucose transport to brain)
  5. Increased Protein (g/L) >0.5, plasma protein leakage due to inflammation
30
Q

What is the typical CSF interpretation in TB meningitis? (5)

A
  1. Opalescent appearance
  2. Increase in WBC per ul
  3. Predominant cells: L**>P
  4. Very high protein
  5. Low glucose <2.2
31
Q

What is the typical CSF interpretation in viral meningitis? (5)

A
  1. Clear appearance
  2. Increase in WBC per ul
  3. Predominant cells: P early, L late
  4. > 0.5 protein (elevated)
  5. Normal glucose
32
Q

CSF interpretation:
1. Clear appearance

  1. Increase in WBC per ul
  2. Predominant cells: L>P
  3. > 0.5 protein (elevated)
  4. <2.2 glucose

Ddx?

A

Cryptococcal meningitis

~TB but TB has opalescent appearance

33
Q

CSF interpretation in subarachnoid hemorrhage?

A
  1. Xanthochromic appearance (yellowish)
  2. Greatly elevated WBCs
  3. Crenated RBC as predominant cells
  4. Very high protein
  5. Normal glucose
34
Q

What is the normal WBC count per ul in CSF?

What is the predominant cell L/P in CSF?

A

<4
- Lymphocytes

Others:
Protein: 0.15-0.45 g/L
Glucose: 2.8-4.2 mmol/L

35
Q

What is defined as significant reduced CSF glucose when compared to plasma glucose?

A

CSF glucose <50% plasma glucose

36
Q

Name 5 causative agents for chronic meningitis?

A
  1. Mycobacterium tuberculosis
  2. Cryptococcus neoformans
  3. Treponema pallidum (syphilis)
  4. Amoeba (Naegleria fowleri)
  5. HIV
37
Q

Both TB and Cryptococcus neoformans can cause granulomatous meningitis.

For TB meningitis, L>P in CSF, and patient has insidious onset of headache, confusion, fever.

How to diagnose TB meningitis? (2)

A
  1. BAL for PCR (sputum is not sensitive enough)

2. CSF for antigen detection

38
Q

What are the risk factors for Cryptococcal meningitis?

A
  1. Immunocompromised: AIDS, malignancy, steroid therapy, DM
  2. SLE
  3. Alcoholism
39
Q

Pathogenesis of Cryptococcal meningitis: Inhalation of yeast > harmless airway colonisation > ______?

Pathology: SOL with granuloma and mucinous exudate

What to expect in CSF investigations?

A

Neurotropic;

  1. Increased opening pressure
  2. India ink +ve
  3. Culture: Sabouraud agar
  4. Serology: Latex agglutination test for antigen - for monitoring treatment response
40
Q

Cryptoccocal meningitis: what test to do other than CSF investigation? (2)

A
  1. Blood culture

2. Latex agglutination test - for monitoring treatment response

41
Q

What is the treatment for Cryptococcal meningitis? (2)

A
  1. IV amphotericin B + flucystosine

2. Life-long fluconazole prophylaxis in AIDS patients

42
Q

What are the risk factors for brain abscess formation? (7)

A
  1. Hematogenous
    - MC infective endocarditis
  2. Contiguous spread:
    - Bronchiectasis, sinusitis, AOM, dental caries
  3. Direct inoculation
    - Open fracture, post-neurosurgical patient
43
Q

What can be observed in CT brain if brain abscess? (2)

A

Ring-enhancing lesion (1) with surrounding vasogenic edema (1)

44
Q

Treatment for brain abscess? (3)

A
  1. Drainage

2. Antibiotics: 3rd generation cephalosporin (cefotaxime/ ceftriaxone) + metronidazole

MICBI - Clinical MICBI (19 decks)

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