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FOS 2 > Gram Pos and Neg > Flashcards

Gram Pos and Neg Flashcards

1
Q

Capsule

  • _______ surrounding bacterial cells
  • Consists of ______ made of single or multiple types of sugar residues
  • Function of capsule
A
  • Viscous gel
  • Polysaccharide
  • Protecting bacteria from immune system by evading phagocytosis and interfering with complement deposition
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2
Q

Bacterial cell wall is made of what compound?

A

Peptidoglycan

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3
Q

Bacterial plasma membranes are exceptionally _______ rich

A

Protein

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4
Q

What is the function of the bacterial plasma membrane

A
  • Permeability and transport of solutes
  • Contains proteins of ETC
  • contains receptors for chemotaxis
  • Site of DNA synthesis
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5
Q

What are the functions of the cell wall?

A
  • Protection from mechanical disruption and turgor pressure
  • Protects from toxic agents
  • Permits exchange of nutrients required for growth
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6
Q

Describe the structure of the cell wall.

A
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7
Q

Gram Positive Bacteria

  • Have a lot of ____ in cell wall
  • Presence of ____ & _____
  • Only ______ cell membrane
  • What compound do they lack on their exterior?
A
  • Peptidoglycan
  • Teichoic & Lipoteichoic acid
  • Single
  • LipoPolySaccharide (LPS)
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8
Q

What is the function of teichoic and lipoteichoic acid in cell wall?

A

They anchor the cell wall to the plasma membrane

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9
Q

Gram Negative Bacteria

  • Thickness of peptidoglycan cell wall?
  • Structure of membrane compared to cell wall?
  • What does the gram negative outer membrane contain?
  • What is the function of the outer membrane?
A
  • Thin (single sheet)
  • Inner membrane –> cell wall –> outer membrane
  • LPS
  • Creates a negative charge due to LPS, which makes it harder for the host immune system to attack the bacteria. Also creates a periplasm that holds important enzymes in.
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10
Q

Describe how gram + and gram - bacteria appear when stained and why.

A
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11
Q

Bacteriostatic

A

Inhibits growth of bacteria but does not kill

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12
Q

Bactericidal

A

Inhibits growth and kills bacteria

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13
Q

What is the most common method of inhibition of bacterial growth?

A

Inhibition of cell wall synthesis and bacterial protein synthesis

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14
Q

Pili

  • Made from what protein?
  • 2 common types?
  • Core of pilus?
A
  • Pilin
  • Adhesion and sex pili
  • Hollow
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15
Q

What is flagellin?

A

A protein subunit that anchors flagella to bacterial cell. Each speices only has a single type and the primary protein structure differes between bacteria. They are highly antigenic.

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16
Q

What are spores? What are all medically important spore formers?

A
  • Small dehydrated metabollically quiescent bacteria that are coated by a keratin like insoluble protein coat. They are heat resistant, pH resistant, and can live for a long time. They become inactive when nutritional conditions are unfavorable or depleted. They can reactive when nutrition is more available.
  • Gram + rods
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17
Q

Shape

  • Coccus?
  • Bacillus?
  • Coccobacillus?
A
  • Round
  • Rod shaped
  • Intermediate between round and rod (oval)
18
Q

When bacteria are grown on non-selective blood agar media, they may lyse the RBCs. What are the different types of hemolysis called?

A
19
Q

What is a fastidious organism?

A

One that requires specialized nutrients to grow

20
Q

What is MacConkey agar?

A

Contains bile salts that inhibit the growth of gram positive organisms. Organisms that are able to survive are gram negative and ferment lactose to form red/pink colonies.

21
Q

What are the 3 virulence factors we need to know?

A

Adhesion

Toxins

Immune response/evasion

22
Q

Are virulence factors always expressed?

A

No - they are often triggered by changes in environment (temp, pH, nutrient availability, osmotic pressure, hypoxia)

23
Q

Only _______ have endotoxin.

A

Gram negative bacteria

24
Q

What is an invasion type 3 secretion system?

A
25
Q

What is endotoxin?

A

When gram negative cells are lysed, they release LPS, which is broken down into an O-antigen region, a core polysaccharide, and the Lipid A anchoring region. The lipid A is the portion that is toxic. At low concentrations it can cause inflammation, but at higher concentrations it can cause fever, hypotension, shock and death.

26
Q

What is an AB toxin?

A
27
Q

What is the difference between endo and exotoxin?

A

Endo - on the bacteria

Exo - secreted by bacteria

28
Q

Cytolitic Exotoxins

  • Secreted by which bacteria?
  • What are 2 exotoxins to know?
A
  • Gram + and gram -
  • Phospholipase C (breaks down membrane phospholipids) and Pore-forming toxins (promote leakage and cell lysis)
29
Q

What are super antigens?

A
  • Exotoxin
  • Produced mostly by Gram +
  • Bind to TCR and promote uncontrolled activation of T cells –> uncontrolled cytokine release –> shock & death
30
Q

Enterotoxin

  • Secreted by gram (+) or gram (-)?
  • Is it stable or easily degraded?
  • Does it require a bacterial cell to exert its effects?
  • What effect does it have on the host?
A
  • Both
  • Heat stable, resistant to gastric acid
  • Do not need active replicating bacteria to have an effect
  • Results in bad nausea by stimualtion of neural gut receptors
31
Q

Staphylococcus aureus

  • Gram staining?
  • Shape?
  • Hemolysis?
  • Catalase test?
  • Coagulase test?
  • Capsulated?
A
  • Gram +
  • Cocci in clusters
  • Beta
  • Positive
  • Positive
  • Yes
32
Q

What toxins are produced by gram +?

A
  • Cytolytic (disrupt membranes and lyse cells)
  • Exfoliative toxins (AB Toxin)
  • Enterotoxin
33
Q

Describe the pathogenesis of S. aureus.

A
34
Q

What are the clinical presentations of S. aureus?

A
35
Q

Streptococcous - E. coli

  • Gram + or -?
  • What do they ferment?
  • What important enzyme do they produce?
  • What are the main 3 antigens on their surface?
A
  • Gram -
  • Ferment lactose
  • Produce tryptophanase
  • O antigen (from LPS), K antigen from polysaccharide capsule, and H antigen from flagellar protein
36
Q

E. coli - Virulence Factors

  • What are the main virulence factors in E. coli (3)
  • Describe the different types of pili on E. coli and how they contribute to the bacteria’s pathogenicity
  • Describe the exotoxins that E.coli secrete
A
  • Pili, Type 3 secretion system, exotoxins
  • Pili
    • Type 1 - binds to epithelial cells
    • P pili - binds to kidney cells
    • Other types bind to enterocytes and cause diarrhea
  • Exotoxins
    • alpha - hemolysin: pore forming cytolysin
    • Shiga toxin: AB toxin that inhibits protein synthesis
37
Q

Describe the pathogenesis of extraintestinal E. coli.

A
38
Q

Describe the pathogenesis of intestinal strains of E.coli that release Shiga Toxin.

A
39
Q

With regards to cellular structure, what features are unique to gram positive cells vs. gram negative cells?

A
40
Q

Gram ____ cells can express beta-lactamases and these enzymes reside in the ______ space.

A

Negative

Periplasmic

FOS 2 (44 decks)

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