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Clinical Micro > Bacterial CNS infections > Flashcards

Bacterial CNS infections Flashcards

1
Q

what is the main element of treatment for CNS infections?

A

treating empirically as soon as possible!

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2
Q

Define: meningitis

A

inflammation of the membranes covering the brain and spinal cord

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3
Q

What is another name for non-bacterial meningitis?

A

aseptic (viral) meningitis

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4
Q

What is another name for bacterial meningitis?

A

purulent meningitis

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5
Q

what is the most common cause of meningitis ?

A

viral infections that usually resolve without treatment

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6
Q

What is the incidence (yearly) of bacterial meningitis in NS?

A

Incidence of 3 cases / 100,000 population / yr

probably 25-30 cases a year in NS

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7
Q

What symptoms are present in 85% of patients presenting with bacterial meningitis?

A

Fever, headache, meningismus, & altered mental status

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8
Q

What is the most common bacterial cause of meningitis?

A

Pneumococcal meningitis

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9
Q

the incidence of meningitis caused by this bacteria has declined since 1895 due to successful vaccination

A

Haemophilus influenza

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10
Q

What is meningismus ?

A

stiffness in the neck and photophobia

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11
Q

How do meningitis causing bacteria establish an infection?

A

all of us carry the bacteria transiently in our throats

if there is damage to the epithelium, the bacteria can colonize, invade the blood then further disseminate to tissues and cerebrospinal fluid

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12
Q

What are the 6 general causes (infectious and non) of meningitis?

A
  1. Bacterial Infections
  2. Viral Infections
  3. Fungal Infections
    - (Cryptococcus neoformans, Coccidiodes immitus)
  4. Inflammatory diseases (SLE)
  5. Cancer
  6. Trauma to head or spine.
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13
Q

What are 5 species of bacteria known to cause meningitis ?

A
  1. S. pneumoniae
  2. N. meningitidis
  3. H. influenzae type B (v rare now)
  4. Listeria monocytogenes (@risk people)
  5. Group B Streptococcus
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14
Q

what virus causes 80% of viral meningitis?

A

Enterovirus

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15
Q

What virus causes a very serious form of meningitis? What can it be treated with?

A

HSV /VZV

Antivirals - Acyclovir

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16
Q

Most viral meningitis cases clear in…

A

3-8 days

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17
Q

What is the #1 cause of meningitis in children aged under 3 months? what’s number 2?

A
  1. Group B streptococci

2. L. monocytogenes

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18
Q

What is the #1 cause of meningitis in children 3-18 months? what’s #2?

A
  1. N. meningitides

2. S. pneumonia

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19
Q

What is the #1 cause of meningitis in people aged 18-50? what’s #2?

A
  1. S. pneumoniae

2. N. meningitidis

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20
Q

What is the #1 cause of meningitis in people aged 50+? what’s #2?

A
  1. S. pneumoniae

2. L. monocytogenes

21
Q

What is ventricomegaly?

A

enlargement of the ventricles

22
Q

Outside of an HSV infection, people with viral meningitis tend to be ___ which is not the case usually with bacterial meningitis

A

Alert and oriented

23
Q

What are symptoms of both bacterial and viral meningitis ?

A 
Headache
low grade fever
photophobia
neck stiffness/pain
vomiting 
rash
24
Q

What is the diagnostic test for bacterial meningitis?

A

A lumbar puncture

25
Q

How is a lumbar puncture conducted?

A

A lumbar puncture collects cerebrospinal fluid to check for the presence of disease or injury.

A spinal needle is inserted, usually between the 3rd and 4th lumbar vertebrae in the lower spine.

26
Q

What is useful about a lumbar puncture?

A

Permits the urgent distinction of bacterial meningitis

from viral meningitis and examination of the CSF allows precise diagnosis

27
Q

What 4 findings are consistent with a BACTERIAL meningitis infection?

A
  1. Presence of NEUTROPHILS in the CSF
  2. Very high WBC count
  3. CSF protein level reflects the degree of meningeal inflammation: 10 X in bacterial infections
  4. CSF glucose levels : very low in bacterial infections
28
Q

What 4 findings are consistent with VIRAL meningitis infections?

A
  1. Presence of LYMPHOCYTES (indicates either viral or mycobacterial infection)
  2. WBC count not usually as high as bacterial
  3. CSF protein level reflects the degree of meningeal inflammation: 2-3 X in viral CNS infection
  4. CSF glucose levels : normal with viral infections
29
Q

Why are sugar levels low in bacterial meningitis infections?

A

Sugar levels are low because you have so much inflammation that sugar transport is impaired

30
Q

What is the morphology of Neisseria meningitidis

A

Gram negative aerobicdiplococcus with a polysaccharide capsule

31
Q

How many serogroups of Neisseria are there? what is it based on?

A

13 serogroups classified by their capsule (5 account foralmost all disease) - A / B / C / Y / W-135

32
Q

What are the most common serogroups of N. meningitidis

33
Q

What agar types will N. meningitidis grow on? Why is this clinically relevant?

A

SBA and chocolate

Will differentiate it from N. gonorrhoea

34
Q

How does N. meningitidis often appear on a gram stain?

A

often appears intracellular

35
Q

What two tests is N. meningitidis positive for?

A

Catalase + and Oxidase +

36
Q

What is a way to differentiate between N. meningitidis, gonorrhoea, and lactamica?

A

What sugars they ferment (?)

N. gonorrhoeae will only ferment glucose
N. meningitidis will ferment glucose and maltose
N. lactamica will ferment all glucose, maltose, and lactose

37
Q

What are 5 symptoms of meningococcocemia?

A 
Rash
Vascular damage
DIC (disseminated intra-vascular coagulation)
Multi-organ failure
Shock
38
Q

How quickly can death occur with meningococcocemia? What is the fatality rate with treatment

A

can die within 24 hours

fatality is 3-10% with treatment

39
Q

What is the transmission like for N. meningitidis? (ie who is it passed between and how?)

A

Human to human only

Transmission by saliva, most often by aerosol effect (coughing, sneezing), kissing etc
- overcrowding increases risk

40
Q

What % of the pop carries N. meningitidis transiently in their throat

41
Q

What is the incubation period for N. meningitidis?

42
Q

What are the 3 vaccines (names and coverage) for N. meningitidis ?

A
  1. menjugate/meningitec - monovalent for serogroup C
  2. menactra - quadrivalent for serogroups A / C / Y / W-135
  3. bexsero - monovalent for serogroup B `
43
Q

[Review] what are the “stats” on L. monocytogenes (morpology, testing profile, hemolysis, growth behaviour) ?

A 
Gram-positive bacilli
Catalase +++
Tumbling motility at 25ºC
Umbrella motility in semi-soft agar
Beta-hemolytic
\+ CAMP test
44
Q

What are 3 clinical manifestations of L. monocytogenes?

A
  1. Meningitis
  2. Abortion or premature delivery of a severely ill or acutely ill infant
  3. Perinatal septicemia
45
Q

What is perinatal septicemia? What often occurs?

A
  • infant often dies within a few minutes or hours
  • symptoms reflect disturbances of respiratory, circulatory or central nervous system
  • if infant survives, meningitis common, often fatal or leads to permanent mental deficiency
46
Q

What is the most important virulence factor that L. monocytogenes has?

A

Listeriolysin O

47
Q

What is Listeriolysin Oresponsible for?

A

ß-hemolysis of RBCs and destruction of phagocytic cells

aids in escape from phagosome

48
Q

What is the treatment plan for someone with suspected bacterial meningitis?

A
  1. If possible (time permitting to get an MRI determining opening pressure) do a lumbar puncture before antibiotics
  2. if not/immediately after, start them on 3rd generation cephalosporin and vancomycin (adults)
    - ampicillin also added if the person is at risk for a L. monocytogenes infection (50+ or kids under 3 mo?)
49
Q

Why are steroids often added concomitantly with antibiotics for treating meningitis?

A

reduce swelling

Clinical Micro (28 decks)

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