Bacterial Meningitis Flashcards

1
Q

Is bacterial meningitis a medical emergency?

A

Yes

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2
Q

Characteristics of bacterial meningitis?

A

Acute onset and high mortality rate

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3
Q

Signs/Symptoms of bacterial meningitis?

A

HA, fever, vomiting, photophobia, stiff neck, irritability, varying degree of neurological dysfunction

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4
Q

Identification of bacterial agents?

A

Spinal tap –> CSF

  • Gram stain
  • Rapid antigen detection
  • PCR testing for specific species in CSF
  • Culture of CSF and blood
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5
Q

Characteristics of CSF of bacterial meningitis?

A
Large number of PMNs (chemotactic response)
Reduced glucose (host stress response)
elevated protein (BBB breakdown)
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6
Q

What bacterial cause of acute meningitis are typical in children from birth to 3 months?

A

Grp B Strep
Gram (-) entero
Listeria monocytogenes

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7
Q

What bacterial cause of acute meningitis are typical in children from 3 months to 2 years?

A

Strep pneumo
Neisseira meningitis
Haemophilus influenzae

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8
Q

What bacterial cause of acute meningitis are typical in children from 2 years to 18 years?

A

Neisseira meningitis

Strep pneumo

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9
Q

What bacterial cause of acute meningitis are typical in immunocompromised patients?

A

Neisseira meningitis
Gram (-) entero
Pseudomonas aeruginosa

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10
Q

Characteristics of streptococci?

A

Gram (+) spherical bacteria that occur in pairs or long chains

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11
Q

What is the most common cause of bacterial meningitis in the US?

A

Strep pneumo

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12
Q

How are Lancefield classifications determined?

A

By an anytigenic carbohydrate substance found in cell walls that determines the Lancefield groups A-H & K-U

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13
Q

Which Lancefield groups cause disease in humans?

A

A,B,C,F, and G

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14
Q

Of what is the amino sugar for grp A?

A

Grp A - rhamnose-N-acetylglucosamide

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15
Q

Of what is the amino sugar for grp B?

A

rhamnose-glucosamine

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16
Q

Of what is the amino sugar for grp C?

A

rhamnose-N-acetylgalactosamine

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17
Q

Of what is the amino sugar for grp D?

A

glycerol teichoic acid

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18
Q

Of what is the amino sugar for grp F?

A

glucopyranosyl-N-acetylgalactosamine

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19
Q

What antigenic specificity is used to type. S. pneumo?

A

Capsular polysaccharides

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20
Q

Colonization of S. pneumo?

A
  1. Adhere tightly to the nasopharyngeal epithelium by multiple mechanisms
  2. May be progression into the lungs or middle ear
  3. Inflammation in the middle ear is caused by pneumococcal cell wall components resulting in cytotoxicity on ciliated cells of the cochlea
  4. Upon reaching the lower respiratory tract by aerosol, can progress to the alveolus and associate with specific alveolar cells which produce a choline-containing surfactant
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21
Q

Invasion of S. pneumo?

A
  1. Can alter vascular permeability to allow access to the blood stream, leading to lung infections and bacteremia.
  2. Can directly invade endothelial cells where the bacteria are transported across the cell and bacteria are expelled into the blood stream
  3. Bacteria can cross the BBB by binding to cerebral capillaries, transmigrate and enter the cerebrospinal fluid leading to meningitis
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22
Q

What are the virulence factors of S. pneumo?

A
Capsule
Pili
Cell Wall Components
Choline Binding protein
Hemolysins:Pneumolysin
Hydrogen peroxide
Neuroaminidase and IgA protease
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23
Q

How does the virulence factor - capsule work for S. pneumo?

A

Interferes with phagocytosis by leukocytes.

Resistance to phagocytosis is brought about by interference with binding of complement C3b to the cell surface

24
Q

How does the virulence factor - pili work for S. pneumo?

A

Enhances bacterial ability to adhere and invade cells

25
Q

How does the virulence factor - Cell Wall components work for S. pneumo?

A

Causes an inflammatory response to the bacteria leading to a pt’s symptoms

26
Q

How does the virulence factor - Choline binding proteins work for S. pneumo?

A

An adhesin that interacts with carbohydrates on the pulmonary epithelial surface. IMPORTANT IN CROSSING THE BBB DURING DEVELOPMENT OF MENINGITIS

27
Q

How does the virulence factor - Hemolysins (Pneumolysins) work for S. pneumo?

A

Protein that can cause lysis of host cells and activate complement

28
Q

How does the virulence factor - Hydrogen Peroxide work for S. pneumo?

A

Produced by pneumococcus and causes damage to host cells (can have bacteriacidal effects)

29
Q

How does the virulence factor - Neuramidase and IgA protease work for S. pneumo?

A

Helps invade host tissues and destroys secreted IgA at the mucosal surface

30
Q

Characteristics of neisseria?

A

Gram (-), non-motile, diplococci

May or may not have a capsule

31
Q

What are the pathogenic Neisseria?

A
Neisseria gonorrhea (gonococcus)
Neisseria meningitis (meningococcus)
32
Q

Meningococcus causes?

A

Meningococcal meningitis and sepsi

33
Q

Prevalence of meningococcus? Mortality?

A

Low

High

34
Q

Carriage rates of meningococcus in those without disease?

A

5 - 30%

35
Q

What differentiates gonococcus from meningococcus?

A

A prominent antiphagocytic polysaccharide capsule

36
Q

What are strains of meningococcus grouped according to?

A

Capsular polysaccharide

37
Q

Pathogenesis of meningococcal meningitis?

A

Begins abruptly with sudden high fever, stiff neck, chills, myalgias, weakness, nausea, vomiting, and headache. Apprehension, restlessness, and delirium occur within the next few hours. Widespread petechial and purpuric skin lesion appear suddenly
Pulmonary insufficiency develops within a few hours and many patients dies within 24 hours even with appropriate antibiotic therapy

38
Q

Early symptoms of meningococcal meningitis?

A

Neck/back stiffness
Mental changes (agitation/confusion/coma)
Petechial/purpuric rash (late sign)

39
Q

What is the major toxin of meningococcus? Mechanism of toxin?

A

Lipooligosaccharie –> endotoxic

40
Q

Other virulence factor of meningococcus?

A

Antiphagocytic polysaccharide capsule

41
Q

What is the only known reservoir for meningococcus?

A

The human nasopharynx

42
Q

How is meningococcus spread?

A

Transmission is through respiratory droplets and aspiration of said particles

43
Q

Where do you meningococcus attach?

A

Nonciliated columnar epithelial cells of the nasopharynx

44
Q

What is meningococcus attachment mediated by?

A

Pili

45
Q

How does meningococcus invade the mucosal cells?

A

Phase variation

-turning off capsule genes then turning it on again once the organism is in the bloodstream

46
Q

Meningococcus vaccines?

A

Menomune: Unconjugated vaccine (carbohydrate only, no memory component)
Menactra: Conjugate to toxoid
Both cover serogrps A,C,Y, and W135

47
Q

Characteristics of Listeria monocytogenes?

A

Gram (+) rods

Facultative intracellular paracite

48
Q

What is required to combat Listeria infection?

A

Cell-mediated immunity

49
Q

In what population is the incidence of Listeria increased?

A

AIDs patients

50
Q

What happens if Listeria infects the uterus?

A

Death of the fetus

51
Q

Where is L. monocytogenes found?

A

Widespread among animals in nature

52
Q

Where is the human reservoir for L. monocytogenes?

A

Intestine and vagina

53
Q

What other type of transmission is important for L. monocytogenes?

A

Food bourne transmisision

54
Q

Where do L. monocytogenes attach and invade?

A

Epithelial cells and marcophages

55
Q

What type of activation is necessary to kill L. monocytogenes?

A

Cytokine activation of macrophages

56
Q

How does L. monocytogenes spread inside humans? Why?

A

Cell-to-cell protecting from humoral immune system

57
Q

Hows is endocytosis mediated in non phagocytic host cells?

A

Bacterial portein, internalin, storage cells,