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Microbiology > Pathogenicity > Flashcards

Pathogenicity Flashcards

1
Q

Infection Cycle

A

the route an organism takes from one individual to another

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2
Q

horizontal transmission

A

from one member of a species to another

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3
Q

examples of contact transmission

A

direct, fomites, droplet

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4
Q

examples of vehicle transmission

A

water, food, air

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5
Q

examples of vector transmission

A

animals (ed, mosquitoes or ticks)

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6
Q

vertical transmission

A

from parent to child

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7
Q

accidental transmission

A

a host who is not part of the normal infectious cycle unintentionally encounters that cycle

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8
Q

Steps in pathogenicity:

A
  1. Exposure & portals of entry
  2. Adherence
  3. Penetration & evasion of host defense
  4. Damage to host cells (disease)
  5. Portals of exit (transmission)
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9
Q

3 Portals of entry:

A

mucous membranes, skin, parenteral route (penetration)

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10
Q

3 places you find mucous membranes

A
  1. Respiratory tract (common cold, influenza)
  2. Digestive tract (polio, cholera)
  3. Genitourinary tract
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11
Q

Skin is:

A

impenetrable to most organisms

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12
Q

Microbes get in through the skin by using:

A

hair follicles, sweat glands, and abrasions

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13
Q

What is the main symptom of tetanus?

A

paralysis

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14
Q

How do you get tetanus?

A

parenteral route

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15
Q

Pathogens use _______ __ ______ best suited to their mechanisms of pathogenesis.

A

portals of entry

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16
Q

Food-borne pathogens come through the:

A

mouth

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17
Q

The respiratory tract cathces:

A

airborne pathogens

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18
Q

What causes typhoid fever?

A

Salmonella typhi

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19
Q

What’s the difference between rubbing Salmonella typhi on the skin as opposed to ingesting it?

A

No reaction when rubbed on the skin but causes typhoid fever when swallowed

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20
Q

ID50:

A

infectious dose for 50% of the test population

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21
Q

LD50:

A

lethal dose (of a toxin) for 50% of the test population

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22
Q

What is the ID50 (# of endospores) needed for B. anthracis to infect someone through the skin?

A

10-50 endospores

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23
Q

What is the ID50 (# of endospores) needed for B. anthracis to infect someone through inhalation?

A

10,000-20,000 endospores

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24
Q

What is the ID50 (# of endospores) needed for B. anthracis to infect someone through ingestion?

A

250,000-1,000,000 endospores

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25
Q

What are the symptoms of gastrointestinal B. anthracis (rare)?

A

GI distress, vomiting of blood, diarrhea

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26
Q

What are the symptoms of pulmonary (inhaled) B. anthracis?

A

flu-like symptoms, then pneumonia

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27
Q

What are the symptoms of cutaneous B. anthracis (most common)?

A

skin lesions and necrotic ulcers

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28
Q

Adhesins/ligands bind to the _________ on host cells

A

receptors

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29
Q

3 examples of adhesins:

A
  1. Glycocalyx: Streptococcus mutans
  2. Fimbriae: Escherichia coli
  3. M protein: S. pyrogenes
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30
Q

Microbes in ______ are sheltered from harmful factors (ex: antibiotics).

A

biofilms

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31
Q

What % of human infections are biofilms involved in?

A

65%

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32
Q

Invasins:

A

some microbes (eg. E. coli or Salmonella) produce protein (invasin) that alters host actin, causes membrane ruffling, microbe is engulfed.

33
Q

How do capsules and cell wall components evade host defenses?

A

prevent phagocytosis

34
Q

How do bacterial enzymes evade host defenses?

A

coagulases, kinases, hyaluronidase, & collagenase

35
Q

What is another way pathogens evade host defense?

A

antigenic variation

36
Q

3 species that prevent phagocytosis:

A

S. pneumoniae, H. influenzae, and B. anthracis

37
Q

What protein resists digestion and where on the microbe is it produced?

A

M protein; produced on the cell surface and fimbriae

38
Q

What species has the M protein?

A

S. pyrogenes (childbirth fever & sore throat)

39
Q

What does mycolic acid do to evade host defenses?

A

resists digestion

40
Q

What species has mycolic acid?

A

Mycobacterium tuberculosis

41
Q

Fibrin and Clots can do what two things?

A
  1. Isolate pathogens to prevent further infection

2. protect some pathogens to hide from host cells

42
Q

coagulases:

A

coagulates fibrinogen (forms blood clot in host)

43
Q

kinases:

A

digest fibrin clots

44
Q

hyaluronidases:

A

hydrolyze hyaluronic acid (breaks down extracellular matrix in host)

45
Q

hyaluronic acid:

A

polysaccharide involved in holding cells together, particularly connective tissue

46
Q

collagenase:

A

hydrolyzes collagen

47
Q

collagen:

A

forms connective tissue of muscles

48
Q

igA proteases:

A

destroy IgA antibodies

49
Q

Antigenic variation:

A

many microbes can alter surgace antigens and evade host defenses

50
Q

Antigenic drift

A

minor changes in capsid proteins caused by mutations that allow the virus to avoid the immune system

51
Q

Antigenic shift

A

If two strains infect the host at the same time, the virsuses will recombine, giving each each virus a mix of the original viruses. This results in an immediate alteration of multiple genes.

52
Q

Pathogens damage host cells by (4):

A
  1. using host nutrients (iron)
  2. causing damage at the site of invasion (cell lysis)
  3. Inducing hypersensitivity (allergy) reactions
  4. Producing toxins that can cause damage throughout the body
53
Q

Toxins

A

poisonous substances produced by microbes

54
Q

Toxincs can (4):

A

Inhibit protein synthesis
destroy blood cells
disrupt nervous system
damage membranes

55
Q

Some different symptoms toxins can cause:

A

fever, cardiovascular disturbances, shock, and diarrhea

56
Q

exotoxins

A

released by bacteria, can act without growth of bacteria and/or distant from site of infection

57
Q

cytolytic toxins

A

membrane-disrupting toxins that causes cell lysis

58
Q

Cytolytic toxins work by either:

A

making protein channels in the plasma membrane OR disrupting the phospholipid bilayer

59
Q

leukocidins

A

lyse white blood cells

60
Q

hemolysins

A

lyse red blood cells

61
Q

streptolysins

A

hemolysins produced by streptococci

62
Q

An AB toxin is an __________ that consists of two subunits: the _ and _ subunits.

A

exotoxin; A & B

63
Q

B subunit:

A

binds to the host cell to deliver the A subunit to the cytoplasm

64
Q

How many B subunits are needed to form a pore for A entry?

65
Q

A subunit:

A

has toxic activity

66
Q

Many A subunits are:

A

ADP-ribosyltransferases

67
Q

Botulinum toxin (C. botulinum)

A

is the most potent known biological toxin. It causes flaccid paralysis by binding to nerve cells and blocking the release of acetylcholine

68
Q

Tetanus toxin (C. tetani)

A

Causes spastic paralysis by blocking glycine release from inhibitory interneuron

69
Q

Cholera toxin (V. cholerae)

A

Causes secretion of electrolytes & fluids (diarhhea). Binds to epithelial cells.

70
Q

Diptheria toxin (Corynebacterium diptheriae)

A

protein synthesis inhibitor

71
Q

C. botulinum, C. tetani, V. cholerae, and C. diptheriae all have:

72
Q

Endotoxins are produced by:

A

gram-negative bacteria ONLY

73
Q

Endotoxins are in:

A

the lipopolysaccharide of the outer membrane

74
Q

As bacteria die _____ _ is released, which causes a massive release of ________ from host cells. This can trigger fever, shock, and death.

A

Lipid A, cytokine

75
Q

shock:

A

life threatening decrease in blood pressure

76
Q

septic shock:

A

shock caused by bacteria

77
Q

endotoxic shock:

A

shock caused by gram-negative bacteria

78
Q

Endotoxins stimulate cytokine secretion by _________ –> __________ & leaky blood vessels –> _________ (low blood pressure) –> shock

A

macrophages; vasodilation; hypotension

79
Q

5 portals of exit/transmission:

A
  1. respiratory tract (coughing & sneezing)
  2. GI tract (feces & saliva)
  3. Genitourinary tract (urine & vaginal secretions)
  4. Skin
  5. Blood (arthropods that bite/needles/syringes)

Microbiology (21 decks)

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