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Microbial world > Lecture 19 and 20 > Flashcards

Lecture 19 and 20 Flashcards

1
Q

Define pathogenicity

A

The ability to cause disease

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2
Q

Define virulence

A

The degree of pathogenicity

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3
Q

What is transmission?

A

Pathogen leaves the reservoir and enters the host via portal of entry

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4
Q

What must a successful pathogen be able to do after transmission

A

Evade primary host defences

Adhere

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5
Q

What is the final step in a successful pathogens journey?

A

Leaving the body and returning to reservoir or new host

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6
Q

Give an example of infectious agents with human reservoirs

A

Staph. aureus, E.coli, chickenpox, hepatitis B, HIV

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7
Q

What is a source of infection?

A

Where the organism comes from in a specific outbreak or individual infection

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8
Q

What name is given to the source of infection from the patient’s own microbiota?

A

Endogenous

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9
Q

What is the opposite of endogenous?

A

Exogenous

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10
Q

Name a zoonotic disease from dogs/rodents

A

Leptospirosis (due to leptospira)

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11
Q

Name some diseases caused by the respiratory tract as a portal of entry

A

Common cold, flu, pneumoan, tuberculosis, measles

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12
Q

What pathogens cause gastroenteritis?

A

Campylobacter
Salmonella enterica/typhi
Some E.coli

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13
Q

What pathogen can cause dysentery?

A

Shigella

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14
Q

What type of hepatitis is food borne (person to person)

A

Hepatitis A

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15
Q

Name two genitourninary tract infections that are non-sexually transmitted.

A 
E.coli (urninary)
Candida infections (thrush)
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16
Q

How can some pathogens gain access through unbroken skin?

A

Hair follicles, sweat gland ducts
hookworm bores through skin
Some fungi grow on keratin

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17
Q

What are two vectors for pathogens?

A

Insects

Formites (medical instruments etc.)

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18
Q

What is infectious doese?

A

Numer of microorganisms required to cause disease

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19
Q

How is virulence expressed quantitatively?

A

ID 50, infectious dose for 50% of the test population

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20
Q

What surface molecules do pathogens produce to adhere to surfaces?

A

Adhesins

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21
Q

Where are adhesins usually found?

A

Fimbria/pilli, which bind specifically to cell surface receptors

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22
Q

What type of molecule are most adhesins?

A

Glycoproteins or lipoproteins

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23
Q

What do some pathogens do to the cell surface?

A

Modify it

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24
Q

How do some E.coli alter the cell surface in order to enable it to adhere?

A

Inject a protein into cells which then acts as a receptor

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25
Q

What % of human infections could be caused by biofilms?

A

Up to 65%

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26
Q

Name 4 biofilm associated infections

A

Contact lens- keratitis
Diabetic foot infection
Prosthetic heart valve endocarditis
Catheter infection

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27
Q

What protein in the cell wall resists phagocytosis in Streptococcus pyogenes?

A

M protein

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28
Q

What cell wall component helps Neisseria gonorrhoeae attach to and enter cells?

A

Opa protein

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29
Q

What waxy lipid reisists digestion by phagocytes and is present in mycobacterium tuberculosis?

A

Mycolic acid

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30
Q

What is the primary antibody defence of mucosa?

A

IgA

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31
Q

How do pathogens overcome IgA?

A

Produce IgA protease

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32
Q

How do pathogens evade the oxygen radicals which phagocytes use to kill them?

A

Produce superoxide dimutase and catalase

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33
Q

What name is given when surface antigens are changed by activating alternative genes?

A

Antigenic variation

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34
Q

Give 3 pathogens that show antigenic variation.

A

Neisseria gonorrhoeae (different opa genes)
Influenza virus
Trypanosoma brucei

35
Q

What is the difference between antigenic shift and antigenic drift?

A

Shift is 2 strains combining

Drift is changing/evolving

36
Q

What do bacteria produce to take up host iron?

A

Siderophores

37
Q

What enzume coagulates fibrin to protect pathogen from phagocytosis?

A

Coagulase

38
Q

What do kinases do?

A

Digest fibrin clots

39
Q

What are spreading factors?

A

Pathogen produced enzymes which break down host tissues, facilitate growth and spread

40
Q

What is the intracellular cement of connective tissue?

A

Hyaluronic acid

41
Q

What spreading factor breaks down hyaluronic acid?

A

Hyaluronidase

42
Q

What breaks down collagen?

A

Collagenase

43
Q

Other then hyaluronidase and collagenase, name other spreading factors

A

Proteases, nucleases, phospholipases

44
Q

What bacteria produce hyaluronidase?

A

Streptococcus spp, staphyloccous aureus, certain Clostridium spp

45
Q

What pathogens produce collagenase?

A

Certain Clostridium spp (Gas gangrene)

46
Q

What does Salmonella prodcue to target the cytoskeleton by altering actin in order to enter a host cell?

A

Invasins

47
Q

What is the primary mechanism of host damage?

A

Toxins

48
Q

What are the two main types of toxin?

A

Endo and exo

49
Q

Whats the difference between endo and exo toxins?

A

Exotoxins: produced inside the cell and transported out
Endotoxins: part of the cell wall of gram-negative bacteria

50
Q

What type of molecule are exotoxins?

A

Proteins

51
Q

What do exotoxins do?

A

Destroy parts of host’s cell or inhibit essential functions

52
Q

What amount of exotoxin is needed?

A

Low amounts

53
Q

How do exotoxins move around the body?

A

Soluble in body fluids

54
Q

What does the body produce in response to exotoxins?

A

Antitoxins (antibodies)

55
Q

Other than antitoxins, how else can the body respond to exotoxins?

A

Heat inactivation

56
Q

What are inactive exotoxins called and where are they used?

A

Toxoids

Vaccines

57
Q

Name two vaccines with toxoids

A

Diptheria and tetanus vaccine

58
Q

What are the three main types of exotoxin?

A

A-B toxins
Membrane disrupting toxins
Superantigens

59
Q

Name an A-B toxin

A

Diptheria toxin

60
Q

Name a membrane disrupting toxin

A

Clostridium perfringens toxin

61
Q

Name a super antigen

A

Staphlococcal toxic shock toxin

62
Q

How do A-B toxins work?

A

B component attaches to host cell receptor, A-B exotoxin enters by endocytosis, components separate, A part alters cell function

63
Q

How does the A part of the A-B toxin alter cell function?

A

Inhibits protein synthesis

64
Q

What does the B part of the Shiga toxin do?

A

Binds to host cell glycolipid in large intestine and kidney

65
Q

What does the A part of the shiga toxin do?

A

Internalised by receptor mediated endocytosis, inactivates rRNA subunit

66
Q

What does A-B endotoxins of diptheria do?

A

Inhibit protein synthesis in heart muscle and other cells

67
Q

What does tetanus toxins (A-B endotoxins) do?

A

Affect neuromuscular junctions by blocking release of inhibitory neurotransmitters

68
Q

What do botulim A-B endotoxins do?

A

Affect neuromuscular junctions, prevents release of acetyl choline

69
Q

What toxin damages membrane using enzymes?

A

C. perfringens toxin

70
Q

What toxin can form pores in host cell membranes?

A

Streptococcus pneumoniae pneumolysin

71
Q

What do superantigens provoke?

A

Intense immune response

72
Q

How do superantigens provoke an intense immune response?

A

Proliferation of T cells

73
Q

What does proliferation of T cells do?

A

Release excessive amounts of cytokines which damage host

74
Q

Give an example of a superantigen

A

Staphloccus aureus enteroxins: causes toxic shock syndrome

75
Q

What is an endotoxin?

A

The lipid portion (Lipid A) of a lipopolysaccharide from gram-negative bacteria

76
Q

How do endotoxins cause fever (pyrogenic response)?

A

Macrophage produces cytokines which induces the hypothalamus to produce prostaglandins which resets the body’s thermostat to a higher temp.

77
Q

Give an example of a virus using mimicry to evade host defence.

A

Rabies virus attachment site resembles acetylcholine

78
Q

How does HIV bind to cells?

A

Binds to CD4 positive cells, CD4 proteins are long and bind to sites in valleys on HIV surface, which can’t be accessed by antibodies

79
Q

How do viruses effect appearance of host cells?

A

Lysis
Appearance of inclusion body
Syncitium formation

80
Q

What are effects of virus infection on appearance of host cell called?

A

Cytopathic effect

81
Q

Round worm causes

A

elephantitis

82
Q

How does round worm cause elephantitis?

A

Blocks lymphatic circulation- lymph accumulates causing swelling

83
Q

What algae produces neurotoxins

A

Alexandrium (produces saxitoxin)

Microbial world (12 decks)

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