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MMI 133 > Mechanisms of Pathogenicity > Flashcards

Mechanisms of Pathogenicity Flashcards

1
Q

Define pathogenicity

A

ability to cause disease

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2
Q

Define virulence

A

the extent to which the microorganism is pathogenic

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3
Q

Define virulence factors

A

molecules/structure produced by pathogens that contribute to their pathogenicity

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4
Q

Some microorganisms have a ____ portal of entry & only capable of causing disease via a ____ route

A

preferred, specific

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5
Q

Ways for pathogens to enter the host cell (5)

A

Most of the time: mucous, skin, parenteral route via mouth

Bypass ways: surgical sites, implants

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6
Q

What determine a pathogen’s tropism? (6)

A
  • distribution of cell receptors for microbes
  • correct host cell types
  • competing microbes
  • nutrients for growth
  • physical and innate defenses
  • environmental condition (eg. pH)
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7
Q

How do pathogens remain at the site of infection and do not have to spread to cause disease?

A

Produce toxins that get into cells

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8
Q

What is the first step of infection?

A

Adherence

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9
Q

How does adherence work?

A

structures on the pathogen called adhesins or ligands (most are glycoprotein or lipoprotein) bind to host cell’s receptors (most are sugars)

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10
Q

What are the factors that allow bacteria to penetrate host defenses? (10)

A
  • capsules (or glycocalyx)
  • cell wall components
  • biofilms
  • enzymes
  • invasins
  • superantigens
  • toxins
  • secretion system
  • antigenic variation
  • intra/extracellular growth
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11
Q

How do capsules (or glycocalyx) protect bacteria?

A

prevent the phagocyte from recognizing and ingesting the bacteria

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12
Q

How do cell wall components protect bacteria?

A

Fc receptors on bacterium binds to Fc area of an antibody to prevent opsonization

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13
Q

How do biofilms protect bacteria?

A

Reduces antibiotic penetration

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14
Q

What are the three exoenzymes bacterial cells release? Describe the function of each exoenzyme.

A

Leucocidin: destroy WBC
Kinase: break down fibrin and dissolve clots formed (important for spread)
Hemolysin: Break down RBC

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15
Q

How do invasins (surface protein) protect bacteria?

A

Activate and rearrange actin and facilitate bacterial engulfment and movement

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16
Q

How do M protein (a cell wall component) protect bacteria?

A
  • heat and acid resistant

- allow attachment of the bacteria to epithelial cells and inhibits phagocytosis

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17
Q

What are 3 types of exotoxins?

A

cytotoxins, neurotoxins, enterotoxins

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18
Q

How do secretion system protect bacteria?

A

Genes encoded on their chromosomes for pathogenic characteristics

(Eg. type III secretion apparatus enables a bacterial cell to inject protein into a host cell)

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19
Q

How do antigenic variation protect bacteria?

A

Immune system sees old pathogens as new ones as they change the makeup of their antigens when replicating

20
Q

Define obligate intracellular bacteria.

A

Bacteria that can only grow inside of host cells

eg. Chlamydia, Rickettsia

21
Q

How do M protein as a cell wall component protect bacteria?

A

Allow attachment of the bacteria to epithelial cells and inhibits phagocytosis

22
Q

How do mycolic acids as a cell wall component protect bacteria?

A

waxy substances in cell walls can prevent bacterium to be digested easily

(eg. M. tuberculosis)

23
Q

What are the three methods of horizontal gene transmission? Define each.

A

Conjugation: transfer of plasmids
Transduction: transfer of DNA from one bacterium into another via bacteriophages.
Transformation: uptake of naked DNA from the environment around the bacterium (extracellular)

24
Q

Define plasmid.

A

small circular DNA molecules separated from the main bacterial chromosome

25
Q

Define bacteriophages. How do they transfer genes?

A

viruses that infect specific bacteria; transduction

26
Q

Plasmid may encode ______ or ______.

A

antimicrobial resistence or virulence factors

27
Q

When do cytopathic effects (CPE) occur?

A

It happens when a pathogen kills or damages the host cell

28
Q

Define syncytium formation. What is its advantage?

A

Infected cells fuse to form a giant cell; permits viral multiplication without exposing virus to antibodies

29
Q

How are genes for exotoxins carried by?

A

Bacteriophages or plasmids

30
Q

Is exotoxin heat labile?

A

Yes

31
Q

Body produces antibodies called ____ for neutralization.

A

antitoxin

32
Q

How do AB toxins cause disease?

A

A: toxic part
B: binds to cells

33
Q

What is endotoxins? How does it affect host cells?

A

lipid A is the endotoxin (heat stable); activate the blood clotting system and can cause shock (life threatening loss of blood pressure)

34
Q

What are two major types of toxin?

A

endotoxin and exotoxin

35
Q

How do superantigen work?

A

Unspecific binding to MHC II and TCR, which results in excessive release of cytokines.

36
Q

How do superantigen work? What does it result?

A
  • Unspecific binding to MHC II and T cell receptor, which results in excessive release of cytokines.

Without: <1% of T helper cells are activated.

With: up to 20% of T helper cells are activated.

37
Q

What is endotoxins? How does it affect host cells?

A

lipid A is the endotoxin (heat stable); activate the blood clotting system and can cause shock (life threatening loss of blood pressure)

38
Q

What are two major types of toxin?

A

endotoxin like LPS

exotoxin like superantigen

39
Q

How do superantigen work?

A
  • Unspecific binding to MHC II and T cell receptor, which results in excessive release of cytokines.

Without: <1% of T helper cells are activated.

With: up to 20% of T helper cells are activated.

40
Q

What does invasin allow pathogen to avoid?

A

Coming in contact with WBC

41
Q

____ is often a primary virulence factor.

A

Toxin

42
Q

How do virus evade immunity? (2)

A

downregulate MHC 1, syncytium formation

43
Q

How do viruses disrupt the cellular life cycles and activity? (3)

A

inhibit the synthesis of host proteins/mitosis
release cause host cells to release enzymes in lysosomes resulting in cell death
deregulate cell function (eg. affect hormone production)

44
Q

How do virus cause cancer? (2)

A

induce chromosomal changes in cells, deregulate contract inhibition (uninhibited cell growth)

45
Q

M protein (cell wall component) is ___ and ____ resistant.

A

heat; acid

46
Q

What is a pathogenicity island?

A

A segment of the bacterial chromosome/plasmid that has multiple genes for virulence factors.

MMI 133 (26 decks)

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