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Pathogenic > Streptococcus Pneumonia > Flashcards

Streptococcus Pneumonia Flashcards

1
Q

Streptococcus Pneumonia
Overview

A
  • G +
  • Cocci, pairs or chains
  • Facultative Anaerobe
  • Catalase -
  • Alpha Hemolysis
  • Virdans Group
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2
Q

S.pneumonia

Encounter

A
  • Normal flora of nasopharynx and oropharynx
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3
Q

S.pneumonia

Entry

A
  • Endogenous source
  • Spread to lung, sinuses, ears, or meninges
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4
Q

S.pneumonia

Spread

A
  • Person to person through respiratory droplets
  • Many people are asymptomatic carriers.
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5
Q

S.pneumonia

Multiplication

A
  • Resist phagocytic clearance by capsule
  • xtcl growth on mucous membranes of the respiratory tract or in blood
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6
Q

S.pneumonia

Damage

A
  • Pneumonia
  • Sinusitis
  • Otitis media
  • Bronchitis
  • Meningitis
  • Bactermia
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7
Q

S.pneumonia

Diagnosis

A
  • Gram stain of sterile tissue or fluid sample
  • BAP Culture
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8
Q

S.pneumonia

Treatment

A
  • Sensitive penicillins/cephalosporins
  • Resistance is on rise*
  • Prevention by accination (to capsular polysaccharide)
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9
Q

**S.pneumonia Characteristics **

A
  • Encapsulated w/ a complex polysaccharide capsule (90 different serotypes)
  • No M protein on its surface.
  • The cell wall contains both lipoteichoic and teichoic acids.
  • Teichoic acids extend beyond capsule to be exposed, called C-polysaccharide.
  • Lipoteichoic acid called F-antigen.
  • Both contain phosphorylcholine which is a unique
  • Requires choline to grow
  • Phosphorylcholine activates cell wall hydrolase which allows breaking of cell wall and filling in with new cell wall biomass
  • Without active hydrolase will stop growing
  • Tissue destruction is mediated primarily by host defense systems.
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10
Q

S. pneumoniae Colonization

A
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11
Q

**S.pneumonia **Virulence Factors

Phosphorylcholine

A
  • Important role in pathogenesis.
  • Can bind platelet active factor (PAF) receptors expressed on the surface of endothelial cells, leukocytes, platelets and tissue cells.
  • Contributes to the acute inflammation response
  • Allows bacteria invasion of cell, bacteria is put in a vacuole that is trafficked to the other side of the cell and released.
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12
Q

S.pneumonia Virulence Factors

Phosphorylcholine Surface Proteins

A
  • CbpA: involved in PAF recptor internalization of bacteria.
  • PspA: Protective antigen, inhibits complement mediated opsonization.
  • PspC: an adhesin targetting host cell secretory component protein (SC)
  • LytA, B and C: autolysins that kill the bacteria upon stationary phase growth and contribute to the inflammation response.
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13
Q

S.pneumonia Virulence Factors

**IgA Protease **

A
  • IgA protease: host IgA traps the bacteria in mucose,
  • IgA protease cleaves antibody allowing escape from mucous.
  • Cleavage of IgA results in capsule disuruption, freeing phosphorylcholine (ChoP in figure) to bind to PAF recpetor.
  • allows tocircumvent removal
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14
Q

S.pneumonia Virulence Factors
Pneumolysin

A
  • pore forming cytotoxin that binds host cell cholesterol
  • Kills ciliated epithelial cells
  • allows to circumvent removal
  • can also bind the Fc Region of human IgG
  • Binding activates the Classical Complement pathway
  • More inflammation
  • Complement cascade lyses cell.
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15
Q

S.pneumonia Virulence Factors
Lack of Catalase

A
  • generates large amount of H2O2.
  • Reactive oxygen species can lead to tissue destruction.
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16
Q

S.pneumonia Virulence Factors

Techoic Acid

A
  • Phoshporylcholine in techoic acid allows it top bind PAF receptor on endothelial cells, WBCs, RBCs, and platelets
  • The bound techoic acid is recognized C3b which activates the alternative complement pathway
  • Increased inflammatory response and efflux of fluid and leukocytes to the site of infection.
  • Complement cascade lyses cells.
17
Q

S.pneumonia Diseases:

Pneumonia

A
  • Fluid from inflammation response is rich in nutrients for bacterial growth.
  • Bacterial growth in turn activates increased inflammation response.
18
Q

S.pneumonia Diseases:

Sinusitis and Otitis media

A
  • Infections of the upper respiratory tract and inner ear.
  • Usually preceded by viral infection of the upper respiratory tract
19
Q

S.pneumonia Diseases:

Bacteremia and Meningitis

A
  • 25-30% of pneumococcal pneumonia patients develop bacteremia due S. pneumonia destruction and invasion of alveolar capillaries.
  • Bacteremia can give access to the meninges, (membrane of brain and spinal cord)
  • Infection and resulting inflammation are refered to as Meningitis

Pathogenic (8 decks)

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