Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Medical Microbiology > CNS Infections > Flashcards

CNS Infections Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

What age groups are susceptible to meningitis?

A

All age groups, but infants, young children, and the elderly are most susceptible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the most common cause of meningitis?

A

Viral meningitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How many cases of viral meningitis occurred from 2009-10?

A

3000 reported cases (actual incidence is likely to be far higher)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How many cases of bacterial meningitis occur in the UK per year?

A

~3200

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How many cases of encephalitis occur in the UK per year?

A

~4400

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

During CNS invasion, where does blood-borne invasion take place?

A

Across the blood-brain barrier to cause encephalitis

Across the blood-brain-cerebrospinal fluid barrier to cause meningitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the blood-brain barrier?

A

Barrier of tightly joined endothelial cells surrounded by glial processes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the blood-brain-cerebrospinal fluid barrier?

A

Barrier of endothelium fenestrations and tightly joined choroid plexus epithelial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How can microbes traverse the blood-brain and blood-brain-cerebrospinal fluid barriers?

A

Growing across, infecting cells that comprise the barrier

Passively transported across in intracellular vacuoles

Carried across by infected WBCs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Give examples of how viruses can invade the CNS

A

Herpes simplex, varicella-zoster and rabies can invade

the CNS via peripheral nerves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

In what ways can the CNS be invaded by microbes?

A

Microbes can traverse the BBB and BBCSF barriers
(often after invasion of the blood stream)

Viruses can invade the CNS via the peripheral nerves

Direct contiguous spread can occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What can cause direct contiguous spread into the CNS?

A 
Sinusitis
Otitis media
Congenital malformations
Trauma,
Direct inoculation during intracranial manipulation

(via the Olfactory portal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the common causes of Meningitis?

A 
Neisseria meningitidis (A, B, C, Y, W-135) (up to 20% carriage)
Streptococcus pneumoniae
Group B streptococcus
Haemophilus influenzae B
Listeria monocytogenes
Gram negatives
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What bacteria can cause chronic meningitis?

A 
Mycobacterium tuberculosis
Mycobacterium avium
Treponema pallidum
Brucellosis
Nocardia sp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What fungi can cause chronic meningitis?

A

Cryptococcus neoformans
Candida sp.
Aspergillus sp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What parasites can cause chronic meningitis?

A 
Taenia solium (beef tapeworm)
Toxoplasma gondii
17
Q

What virulence factors does Neisseria meningitidis possess?

A 
Capsule
IgA protease
Pili
Endotoxin
Outer membrane proteins
18
Q

What virulence factors does Haemophilus influenzae possess?

A 
Capsule
IgA protease
Pili
Endotoxin
Outer membrane proteins
19
Q

What virulence factors does Streptococcus pneumoniae possess?

A

Capsule

IgA protease

20
Q

During meningitis infection, what occurs as a result of damage due to inflammation?

A

Vascular endothelial injury and increased blood-brain barrier permeability leads to entry of many blood components into the subarachnoid space

Neutrophils migrate from the bloodstream and penetrate the damaged blood-brain barrier, leading to profound neutrophilic pleocytosis

Vasogenic oedema and elevated CSF protein levels

21
Q

How does meningitis pathogenesis progress?

A

In less severe cases the inflammatory process remains confined to the subarachnoid space and the pial barrier is not penetrated, and the underlying parenchyma remains intact

In more severe forms of bacterial meningitis, the pial barrier is broken, and the underlying parenchyma is invaded by the inflammatory process

Exudates extend throughout the CSF, particularly to the basal cisterns, damaging cranial nerves (eg, cranial nerve VIII, with resultant hearing loss), obliterating CSF pathways (causing obstructive hydrocephalus), and inducing vasculitis and thrombophlebitis (causing local brain ischemia)

Bacterial meningitis may lead to widespread cortical destruction, particularly when left untreated

22
Q

What are the risk factors for Neisseria meningitidis?

A

Complement defects:

  • Properdin defects
  • Deficiencies in terminal complement components (e.g. membrane attack complex, C5-C9);
    • surprisingly associated with lower mortality rates

Previous viral infection, chronic medical illness, corticosteroid use, and active or passive smoking

Overcrowding e.g university halls and military facilities

23
Q

What are the symptoms of meningitis?

A

Headache: 75-90%
Photophobia: uncommon

On examination:
Fever: 95%
Stiff Neck: 85%
Altered mental status: 80%
All three: 40%
Any one of the three: 100%

Symptoms develop with hours or within 1 to 2days

Non-blanching rash is seen classically with N. meningitidis but can occur with other bacterial and viral infections

Endotoxic shock with vascular collapse is characteristic of severe N. meningitidis infection

Altered mental status, from irritability to somnolence, delirium, and coma, can develop

24
Q

What complications can occur with meningitis infection? (13)

A 
Hearing loss
Cortical blindness
Other cranial nerve dysfunction
Paralysis
Muscular hypertonia
Ataxia
Multiple seizures
Mental motor retardation
Focal paralysis
Ataxia
Subdural effusions
Hydrocephalus
Cerebral atrophy
25
Q

What are the mortality rates of meningitis?

A

N. meningitidis 3-13%
S. pneumoniae 19-26%
H. influenzae 3-6%
L. monocytogenes 15-29%

Patients with meningococcal meningitis have a better prognosis (mortality rate of 4-5%) than do those with pneumococcal meningitis

Patients with meningococcemia have a poor prognosis, with a mortality rate of 20-30%

26
Q

What is the treatment recommended for bacterial meningitis in patients aged 0-4 weeks?

A

Ampicillin plus cefotaxime or an aminoglycoside

27
Q

What is the treatment recommended for bacterial meningitis in patients aged 1-3 months?

A

Ampicillin plus cefotaxime plus vancomycin*

Vancomycin is added to the initial regimen if the presence of penicillin-resistant S. pneumoniae i suspected or if a high incidence of resistance is reported in the community

28
Q

What is the treatment recommended for bacterial meningitis in patients aged 3 months - 50 years?

A

Ceftriaxone or cefotaxime plus vancomycin*

Vancomycin is added to the initial regimen if the presence of penicillin-resistant S. pneumoniae i suspected or if a high incidence of resistance is reported in the community

29
Q

What is the treatment recommended for bacterial meningitis in patients aged 50 years or older?

A

Ampicillin plus ceftriaxone or cefotaxime plus vancomycin*

Vancomycin is added to the initial regimen if the presence of penicillin-resistant S. pneumoniae i suspected or if a high incidence of resistance is reported in the community

30
Q

What is the treatment recommended for bacterial meningitis in patients with impaired cellular immunity?

A

Ampicillin plus ceftazidime plus vancomycin*

Vancomycin is added to the initial regimen if the presence of penicillin-resistant S. pneumoniae i suspected or if a high incidence of resistance is reported in the community

31
Q

What is the treatment recommended for bacterial meningitis in patients who have had neurosurgery, head trauma, or a CSF shunt?

A

Vancomycin plus ceftazidime

32
Q

What tests are performed if a diagnosis of meningitis is suspected?

A

CSF:

  • Complete cell count
  • Differential leucocyte count
  • Examination of Gram stained smear
  • Determination of glucose and protein concentrations in CSF (clinical biochemistry)
  • Latex antigen test
  • Culture
  • PCR

Blood:

  • Full blood count
  • Haematocrit
  • Culture
33
Q

What is the purpose of a CSF gram stain?

A

CSF Gram stain permits rapid identification of
the bacterial cause in 100% specific 60-90%
sensitivity

34
Q

When is a CSF acid fast stain performed?

A

Acid fast stain if M. tuberculosis or M. avium is suspected

35
Q

Give examples of what can be seen with a CSF gram stain

A

Streptococcus pneumoniae - Gram positive cocci in singles and pairs

Neisseria meningitidis - Gram negative diplococci in singles and pairs

Haemophilus influenzae - Gram negative coccobacilli

Listeria monocytogenes - Gram positive rods

36
Q

How are samples cultured if meningitis is suspected?

A

Blood/chocolate agar
Incubated with 5% CO2
18- 24 h at 35-37oC

Medical Microbiology (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions