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Term IV: Infectious Disease > Streptococcus pneumoniae > Flashcards

Streptococcus pneumoniae Flashcards

1
Q

Streptococcus pneumoniae (aka pneumococcus):

Shape
Configuration
Gram stain
Catalase state
Optochin susceptibility
Solubility in bile salts
A 
Round or rod-shaped
Pairs or chains
Gram +
Catalase (-)
Op susceptible
Dissolve in bile salts
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2
Q

What type of pneumococcal disease is unchanged since pre-antibiotic era?

A

Age relationship invasive pneumococcal disease

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3
Q

What molecule traverses cell wall of streptococcus pneumoniae, allows bacteria to adhere to cells, interacts with TLR’s, and stimulates inflamm responses?

A

Lipoteichoic acid

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4
Q

What is alpha-hemolysin?

A

Toxin produced by pneumococcus - Breaks down hemoglobin on blood agar plates so they turn green

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5
Q

What is placed in middle of plate to identify Streptococcus pneumoniae?

A

Optochin disk – diffuses across agar – clear area around the optochin disk is where bacteria are killed

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6
Q

Name 4 diseases caused primarily by pneumococcus.

A

Pneumonia, otitis media, acute sinusitis, meningitis

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7
Q

What is the outermost layer of Strep pneumoniae? How does this help pneumococcus survive?

A

Polysaccharide capsule:

1) not recognized by receptors on PMNs
2) prevents PMN receptors from interacting with Fc of IgG (which can diffuse through capsule and bind cell wall)

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8
Q

What substances do Strep pneumoniae produce that cause disease by stimulating an intense inflammatory response?

A

Peptidoglycan and pneumolysin

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9
Q

Where in the body do pneumococci colonize? What part of population do they commonly spread through?

A

Nasopharynx - kids

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10
Q

T or F. Pneumococci extensively damage tissues by releasing lots of toxins and enzymes.

A

FALSE - primarily causes disease by inducing an inflammatory response and interfering with normal clearance mechanisms

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11
Q

In general, why is antibody ineffective against gram + bacteria?

A

The thickness of the cell wall

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12
Q

Association with what additional type of infection is associated with pneumococcus? How does it interfere with normal clearance mechanisms?

A

Viral - damages ciliary activity, increases mucous secretions, causes edema

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13
Q

What toxin do streptococci produce that makes the colonies collapse in the center and self-destruct in vitro? What does it do in vivo?

A

Autolysin

In vivo - causes inflammation and damages tissues

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14
Q

What is the definitive identification for pneumococcus?

A

If colonies dissolve in bile salts

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15
Q

Immunologic differences in _____ ______ is the basis for distinguishing 93 pneumococcal serotypes.

A

capsular polysaccharides

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16
Q

What is serotyping?

A

Use of Ab present in serum to distinguish among isolates of a single species

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17
Q

Which TLR does lipoteichoic acid primarily interact with?

What unique substances does it contain?

What protein produced by liver in inflammatory diseases/infections reacts with this substance?

A

TLR2»» TLR4

Choline-rich C-polysaccharide - important proteins that render pneumococcus virulent attach to this choline

C reactive protein

18
Q

What proteins are being studied as possible replacements for capsular polysaccharide vaccines?

A

Choline-binding proteins - antibodies against these may enable phagocytosis

19
Q

What is the best studied choline-binding protein and what might its function be?

A

PspA - pneumococcal surface protein A

Anti-phagocytic function

20
Q

What virulence factor produced by pneumococci activates complement, damages ciliated cells, and reproduces changes of pneumonia?

A

Pneumolysin

21
Q

How is pneumococcus spread?

A

Close contact - intimate facial contact, hand to hand, aerosol (sneezing, coughing)

22
Q

What must bacteria first adhere to to cause disease? What do pneumococci specifically use for this adhesion?

A

Epithelial cells

Use lipoteichoic acid

23
Q

When bacteria are present in sufficient number to be cultured and if they cause no symptoms or signs of infection, we call this _____

A

Colonization

24
Q

T or F. If an organism has caused an infection, it has also colonized.

A

FALSE - some organisms like Mycobacterium tuberculosis or Treponema pallidum NEVER colonize - their presence only indicates infection.

25
Q

If organisms are invading tissues and proliferating but not causes symptoms, it is called _____

A

Subclinical or latent disease

26
Q

What two ways does disease result from pneumococcus infection?

A
  1. Organisms carried by secretions to areas of poor clearance
  2. Local invasion through respiratory epithelial cell layers into blood or lymph
27
Q

What two ways does pneumococcus get into trachea, bronchi, lungs?

A
  1. Aspiration - mouth contents bypass glottis, end up in trachea (during sleep)
  2. Inhalation - breathing in aerosolized organisms
28
Q

How do bacteria reach distal bronchioles or alveoli?

A

When ciliary action and cough are not operative- result of smoking, inflammation, viral infection, alcohol, codeine, morphine

29
Q

What builds up in alveoli as a result of bacterial infection? What is this build up called?

A

WBCs, plasma constituents, and RBCs

Infiltrate

30
Q

What is pneumonia?

A

Inflammation of the lungs - fluid build up in alveoli

31
Q

What can compromise clearance?

A

Concomitant viral infection (damages ciliary clearance AND increases expression of receptors that pneumococci adhere to), allergy, air pollutants

32
Q

What factors predispose someone to infection?

A

Decreased pulmonary clearance, diminished neutrophil function, defective IgG production, extremes of life, prior hospitalization, malnutrition, alcoholism, absence of a spleen!!!

33
Q

Why does absence of a spleen predispose someone to infection?

A

Spleen can clear bacteria in absence of opsonizing antibody

34
Q

What are clinical manifestations of pneumonia?

A

Preceded by viral illness with distinct deterioration at onset of pneumonia, shaking, chill, fever, cough, sputum production, chest pain, abnormal chest exam (dullness to percussion, wheezes, rales), infiltrates in CXR

35
Q

What are lab findings of patient with pneumonia?

A

High WBC w/ left shift (increased PMN’s), pO2 and pCO2 are both low

36
Q

What diagnostic tests can you run to determine if someone has pneumonia? What is the proper/best diagnosis?

A

Sputum, blood culture, urine antigen test, CXR

CXR

37
Q

Outside of an outbreak of meningococcal infection, what is most common cause of meningitis?

A

Streptococcus pneumoniae

38
Q

How do vaccinations against pneumococcus vary in adults and infants/children?

A

Adults - Pneumovax - capsular polysaccharide vaccines of 23 serotypes that stimulate T cell independent immune rxn

Children - Prevnar - protein and polysaccharide conjugate vaccine - alters mode of presentation, stimulates Ab in nasopharynx, preventing colonization

39
Q

Why are polysaccharide vaccines not protective before 2 years of age?

A

Immature immune response to polysaccharides

40
Q

What is herd effect?

A

Protect/vaccinate enough members of society, and everyone else will be protected

41
Q

What are bacterial replacement strains?

A

Strains that are not used in vaccines and consequently increase in prevalence

Term IV: Infectious Disease (13 decks)

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