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NMSK B Test 1 > 2.4 Acute Bacterial Meningitis > Flashcards

2.4 Acute Bacterial Meningitis Flashcards

1
Q

How can pathogens infect the CNS?

A
  • Hematogenously
  • Peripheral nerves
  • Olfactory neurons
  • Local injury or congenital defect
  • Pathogens transverse the blood brain barrier
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2
Q

What are the three ways that pathogens can transverse the BBB?

A
  • Transcellular traversal: Through the cell
  • Paracellular traversal: between cells
  • Trojan horse mechanism: Macrophage
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3
Q

What is meningitis?

A

infection of the meninges after crossing blood-CSF barrier

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4
Q

What is encephalitis?

A

infection of the cerebral cortex after crossing the BBB

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5
Q

What is Myelitis?

A

Infection of the spinal cord, usually by viruses

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6
Q

What is post infectious encephalitis?

A

Usually 2-3 weeks after an infection elsewhere in the body, peripheral immune cells gain access to brain through BBB

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7
Q

What are defining characteristics of bacterial meningitis?

A
  • May be preceded by upper respiratory tract or ear infection
  • Growth in CSF initially unimpeded, then attracts PMNs, which lyse to release toxic factors leading to necrosis and edema, and reduced glucose transport in the arachoid & pia matar.
  • Thus, the CSF will have a high level of leukocytes, primarily neutrophils & a low level of glucose.
  • Inflammation impedes CSF flow leading to cerebral edema, hypoxia of the cerebral cortex & irreversible ischemic damage
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8
Q

What are the normal symptoms of bacterial meningitis in children and adults?

A
  • Fever, headache & nuchal rigidity
  • Altered mental status
  • Brudzinski or Kernig sign present
  • Loss of consciousness
  • Purulent nasal discharge
  • Grand mal or focal seizures
  • Focal neurological findings
  • May progress to coma and/or death
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9
Q

What are the symptoms of bacterial meningitis in infants and neonates?

A
  • Fever, lethargy & irritability
  • Poor feeding
  • High-pitched cry
  • Respiratory distress
  • Bulging fontanelle
  • Hypotonia
  • Jaundice
  • Rash
  • Seizures
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10
Q

What bacteria are most likely in meningitis of age 0-4 weeks?

A
  • Step agalactiae (GBS)
  • Escherichia coli
  • Listeria monocytogenes
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11
Q

What bacteria are most likely in meningitis of age 4-12 weeks?

A
  • S. agalactiae
  • E. coli
  • H. influenzae
  • S. pneumoniae
  • N. meningitidis
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12
Q

What bacteria are most likely in meningitis of age 3 months to 18 years?

A
  • N. meningitidis
  • S. pneumoniae
  • H. infuenzae
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13
Q

What bacteria are most likely in meningitis of age 18-50 years old?

A
  • S. pneumoniae
  • N. meningitidis
  • H. influenzae
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14
Q

What bacteria are most likely in meningitis of age greater than 50 years old or immunocompromised?

A
  • S. pneumoniae
  • N. meningitidis
  • L monocytogenes
  • Aerobic Gram-negitive bacilli
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15
Q

What does a bacterial CNS infected CSF profile look like?

A
  • Opening pressure: Elevated
  • Clarity: Turbid; may clot
  • Protein: Increased
  • Glucose: decreased
  • CSF: Serum glucose ratio less than 0.3
  • WBC: increased
  • Gram stained, acid fast, India ink: Shows organisms in about 75% of untreated cases
  • Culture: Organisms grow in 85% of untreated cases
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16
Q

What are the age risk factors for bacterial meningitis?

A

-infants are at higher risk for bacterial meningitis than people in other age groups; vaccines have “pushed” the disease to adults instead of children

17
Q

What are the community setting risk factors bacterial meningitis?

A

College students living in dormitories and military personnel are at increased risk for meningococcal meningitis

18
Q

What recent disease risk factor does bacterial meningitis?

A

Recent upper respiratory tract infection or ear infection

19
Q

What other risk factors are there for bacterial meningitis?

A
  • Weakened immune system due to certain diseases, medications, or surgical procedures
  • Working with meningitis-causing pathogens
  • Travel to the meningitis belt in sub-Saharan Africa or to Mecca during the annual Hajj and Umrah pilgrimage
20
Q

What are general characteristics of Steptococcus pneumoniae?

A
  • Gram-positive cocus
  • Diplococci or short chains
  • Facultative anaerobic
  • Encapsulated
  • Optochin sensitive
  • Bile-soluble (cells are lysed) whereas all other α-hemolytic streptococci are bile-resistant
  • Mixing a suspension of pneumococci with type-specific antisera increases the visibility of the capsule in the microscope, and is the basis of the quellung reaction or capsular swelling test
21
Q

Is Steptococcus pneumoniae catalase positive or negative?

A
  • Negative catalase
22
Q

What is the hemolytic type of Steptococcus pneumoniae?

A

-Alpha-hemolytic

23
Q

What is disease does Steptococcus pneumoniae?

A
  • Otitis media
  • Pneumonia*
  • Bacteremia/sepsis
  • Meningitis
24
Q

When does the most occurrences of Steptococcus pneumoniae occur?

A

• More common during the winter and early spring.

25
Q

What is transmission routes of Steptococcus pneumoniae?

A
  • Inhabitant of oropharynx and nasopharynx
  • Direct person-to-person transmission via respiratory droplets is rare
  • Humans only reservoir
26
Q

What are the virulence factor of Steptococcus pneumoniae?

A
  • Polysaccharide capsule
  • Antiphagocytic by inhibiting complement deposition and phagocytosis when type-specific opsonic antibody is absent
    • > 90 known serotypes based on capsular polysaccharides
  • IgA protease
  • Pneumolysin
    * A cholesterol-dependent cytolysin that creates pores in cholesterol-containing membranes, thus causing host cell lysis
27
Q

How do you diagnosis Streptococcus pneumoniae?

A
  • Isolated from specimens of CSF

* Latex agglutination test

28
Q

How do you diagnosis treatment?

A
  • Up to 15% of invasive pneumococcal isolates are resistant to penicillin in some parts of the U.S
  • Vancomycin combined with ceftriazone is used commonly for empiric treatment, followed by monotherapy with an effective cephalosporin, fluoroquinolone or vancomycin
29
Q

What are the general characteristic of Streptococcus agalactiae?

A
  • Spherical, Gram-positive cocci in chains
  • Catalase-negative
  • CAMP-positive = enhanced hemolysis in the presence of Staphylococcus aureus
  • Bacitracin Resistant
30
Q

What diseases Streptococcus agalactiae?

A
  • Bloodstream infections
  • Pneumonia
  • Skin & soft-tissue infections
  • Bone & joint infections
  • Sepsis
  • Meningitis (rarely)
31
Q

Where does commensal normally Streptococcus agalactiae?

A
  • GBS asymptomatically colonizes the lower gastrointestinal and genitourinary tracts
  • Not harmful in nonpregnant women, and is a dynamic condition as GBS may come and go over months

NMSK B Test 1 (27 decks)

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