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bacteria shizz > IC17 Bacterial meningitis > Flashcards

IC17 Bacterial meningitis Flashcards

1
Q

What is meningitis?

A

Inflammation of meninges (protective layers of the brain)

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2
Q

What are the possible causes of meningitis?

A
  1. infection (bacteria, virus, fungi, parasite, mycobacterium, syphilis)
  2. drugs (co-trimoxazole, ibuprofen)
  3. autoimmune disease
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3
Q

Describe the pathogenesis of bacterial meningitis (how one gets infected)

A

low immunity/prolonged exposure to likely pathogens –> predisposes one to infection and colonization –> bacteria gain entry into the body –> enters CNS and colonizes meninges in a susceptible host –> bacterial meningitis

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4
Q

What are some factors that predisposes one to infection and colonization by likely bacteria?

A
  • immunosuppressed
  • prolonged close contact w infected person
  • travel to endemic areas
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5
Q

What are the various mechanisms of entry for bacteria?

A
  • invade mucosal surface (eg. respi tract) –> hematogenous spread (blood) to brain
  • spread from para-meningeal focus (otitis media, sinusitis)
  • penetrating head trauma
  • anatomical defects in meninges
  • previous neurosurgical procedure
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6
Q

Therefore, what are the possible risk factors for bacterial meningitis?

A
  • immunosuppression
  • local infection (otitis media, pharyngitis, sinusitis)
  • head trauma
  • CNS shunt
  • neurosurgical patients
  • CSF fistula/leak
  • congenital defects
  • splenectomy
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7
Q

What are the patient populations that bacterial meningitis more commonly occurs in?

A
  • male > female
  • children
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8
Q

What are the symptoms of bacterial meningitis? (Subjective factors)

A
  • classic triad (headache, backache, neck rigidity)
  • fever, chills
  • mental status change (irritability)
  • photophobia
  • GI: N/V, anorexia, poor feeding habits in infants
  • derm: petechiae, purpura
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9
Q

What are the physical examinations performed that aids in the diagnosis of bacterial meningitis?

A
  1. Kernig sign
    lay flat on surface, raise thighs up 90 deg to body and try to extend leg fully (ie. extend hamstring)
    (+) = patient experiences back pain
  2. Brudzinski sign
    lay flat on surface, try and elevate head
    (+) = hips and knees will tilt up due to severe neck stiffness
  3. Bulging fontane in children
    alot of inflammation occuring in brain
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10
Q

What are the cultures taken when diagnosing bacterial meningitis?

A
  • blood culture
  • CSF culture
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11
Q

What is the procedure performed to obtain CSF?

A

Lumbar puncture (LP)/spinal tap

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12
Q

What do you look out for when performing LP?

A
  • elevated opening pressure
  • gram-stain & culture
  • composition
  • PCR
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13
Q

By performing visual inspection of CSF, how can we tell if meningitis is bacterial in nature?

A

bacterial = cloudy CSF
no ifxn/viral = clear CSF

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14
Q

What are the components of CSF that are tested?

A
  • glucose
  • protein
  • wbc
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15
Q

What is the normal glucose CSF:blood ratio in a healthy patient?

A

> 0.66

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16
Q

What is the glucose CSF:blood ratio in a patient with bacterial meningitis?

A

< 0.4
(bacteria use up glucose = low glucose)

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17
Q

What is the glucose CSF:blood ratio in a patient with viral meningitis?

A

normal (>0.66) to slightly low

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18
Q

What is the normal conc of protein found in CSF of a healthy patient?

A

< 0.4 g/L

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19
Q

What is the protein conc in the CSF of a patient with bacterial meningitis?

A

raised
> 1.5 g/L

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20
Q

What is the protein conc in the CSF of a patient with viral meningitis?

A

normal (<0.4) to slightly raised

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21
Q

What is the normal WBC count in the CSF of a healthy patient?

A

none
< 5 cells/mm3

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22
Q

What is the WBC count in the CSF of a patient with bacterial meningitis?

A

raised
>100 cells/mm3
mostly neutrophils (ie. pleocytosis)

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23
Q

What is the WBC count in the CSF of a patient with viral meningitis?

A

raised
5-1000 cells/mm3
mostly lymphocytes

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24
Q

What would be seen in general lab findings (eg. WBC, cRP, procalcitonin)

A

signs of systemic infection

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25
Q

Is radiology (MRI/CT brain) required for the diagnosis of bacterial meningitis?

A

no

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26
Q

Then when is it indicated?

A

concern for brain shift during LP due to brain herniation due to mass lesion

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27
Q

What are the likely pathogens causing bacterial meningitis in neonates (<1 month)?

A
  • Strep agalactiae (Grp B Strep)
  • E Coli
  • Listeria monocytogenes
28
Q

What are the likely pathogens causing bacterial meningitis in infants & children (1-23 months)?

A
  • Strep agalactiae
  • E Coli
  • Strep pneumoniae
  • Neisseria meningitidis
29
Q

What are the likely pathogens causing bacterial meningitis in children & adults (2-50 y/o)?

A
  • Strep pneumoniae
  • Neisseria meningitidis
30
Q

What are the likely pathogens causing bacterial meningitis in older adults (>50 y/o)?

A
  • Strep pneumoniae
  • Neisseria meningitidis
  • Listeria
  • Aerobic G(-) (eg. E Coli, Klebsiella)
31
Q

how to rmbr bacteria (read if forgotten :()

A

listeria only for most young & most old age grp due to their impaired immunity

strep agalactiae + E Coli come tgt (in first 2 age grps only)

strep pneumoniae + neisseria occurs in grps 2, 3, 4

32
Q

Which symptom points to Neisseria meningitidis bacteria?

A

derm - petechiae, purpura

33
Q

What are the empiric antibiotics to start for neonates (<1 month) suspected of bacterial meningitis?

A

Likely pathogens: Strep agalactiae, E Coli, Listeria

ceftriaxone + ampicillin

34
Q

What do the two antibiotics cover?

A

ampicillin: Listeria
ceftriaxone: covers everyt else

35
Q

What are the empiric antibiotics to start for infants & children (1-23 months) suspected of bacterial meningitis?

A

Likely pathogens: Strep agalactiae, E Coli, Strep pneumoniae, Neisseria

ceftriaxone + vanco

36
Q

What do the two antibiotics cover?

A

ceftriaxone: everyt
vanco: possible strep pneumoniae strains resistant to ceftriaxone

37
Q

What are the empiric antibiotics to start for children & adults (2-50 y/o) suspected of bacterial meningitis?

A

Likely pathogens: Strep pneumoniae, Neisseria

ceftriaxone + vanco

38
Q

What are the empiric antibiotics to start for older adults (>50) suspected of bacterial meningitis?

A

Likely pathogens: Strep pneumoniae, Neisseria, Listeria, Aerobic G(-)

ceftriaxone + ampicillin + vanco

39
Q

What is the duration required for empiric therapy in the event of NEGATIVE CULTURE (ie. culture does not tell us identity of microbe at all)?

40
Q

What is the best narrow spectrum antibiotics to step down to for bacterial meningitis (that covers neisseria, strep pneumoniae, strep agalactiae, listeria) assuming they are penicillin susceptible?

A
  • Pen G
  • Ampicillin
41
Q

What are the possible antibiotics for Neisseria meningitidis assuming the strain is resistant to penicillin / mild penicillin allergy?

A

ceftriaxone

42
Q

What is the duration of active abx required against Neisseria?

43
Q

What are the possible antibiotics for strep pneumoniae assuming the strain is resistant to penicillin but susceptible to cephalosporins?

A

ceftriaxone

44
Q

What are the possible antibiotics for strep pneumoniae assuming the strain is resistant to both penicillin & cephalosporins?

A

vanco + rifampicin

45
Q

What is the duration of active abx required against strep pneumoniae?

A

10-14 days

46
Q

What are the possible antibiotics for strep agalactiae assuming the strain is resistant to penicillin / mild penicillin allergy?

A

ceftriaxone

47
Q

What is the duration of active abx required against strep agalactiae?

A

14-21 days

48
Q

What are the possible antibiotics for Listeria assuming the strain is resistant to penicillin / mild penicillin allergy?

A
  • co-trimoxazole
  • meropenem
49
Q

What is the duration of active abx required against listeria?

A

at least 21 days

50
Q

What adjunctive therapy can be considered for bacterial meningitis?

A

corticosteroids - dexamethasone

51
Q

What are the criteria to use adjunctive dexamethasone?

A
  • bacterial meningitis
  • ≥6 weeks old
  • caused by strep pneumoniae/H influenzae
52
Q

What are the benefits of using dexamethasone for bacterial meningitis?

A
  • less hearing loss a/w strep pneumoniae & H influenzae meningitis
  • decreased mortality in strep pneumoniae meningitis
53
Q

What are the risks of using dexamethasone for bacterial meningitis?

A
  • ADR (mental status change, hyperglycemia, HTN)
  • ↓ abx penetration
54
Q

What is the adult dose of dexamethasone?

A

10mg q6h for up to 4 days

55
Q

When do we administer dexamethasone?

A
  • 10-20 mins before first dose of abx
  • same time as first dose of abx
56
Q

How long do most patients take to improve clinically?

57
Q

What can we do if patient does not improve after that duration?

A

brain imaging to detect cerebrovascular complications

58
Q

What are the other two monitoring parameters?

A
  • ADR to abx
  • morbidity (common in bacterial meningitis)
59
Q

Chemoprophylaxis is available against what pathogen?

A

Neisseria meningitidis

60
Q

Who needs to take chemoprophylaxis?

A

close contacts (household/day care) + exposure to oral secretion

61
Q

What are the antibiotics available for chemoprophylaxis?

A
  1. rifampicin
  2. ciprofloxacin
  3. ceftriaxone
62
Q

What is the adult dose of rifampicin for chemoprophylaxis?

A

600mg q12h for 4 doses

63
Q

What is the children dose of rifampicin for chemoprophylaxis?

A

10mg/kg q12h for 4 doses

64
Q

What is the infant (<1 month) dose of rifampicin for chemoprophylaxis?

A

5mg/kg q12h for 4 doses

65
Q

What is the adult dose of ciprofloxacin for chemoprophylaxis?

A

500mg PO 1 dose

66
Q

What is the dose of ceftriaxone for chemoprophylaxis?

A

125-250mg IM 1 dose

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