Lecture 19 and 20

Question 1

Define pathogenicity

Answer 1

The ability to cause disease

Question 2

Define virulence

Answer 2

The degree of pathogenicity

Question 3

What is transmission?

Answer 3

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

Question 4

What must a successful pathogen be able to do after transmission

Answer 4

Evade primary host defences

Adhere

Question 5

What is the final step in a successful pathogens journey?

Answer 5

Leaving the body and returning to reservoir or new host

Question 6

Give an example of infectious agents with human reservoirs

Answer 6

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

Question 7

What is a source of infection?

Answer 7

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

Question 8

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

Answer 8

Endogenous

Question 9

What is the opposite of endogenous?

Answer 9

Exogenous

Question 10

Name a zoonotic disease from dogs/rodents

Answer 10

Leptospirosis (due to leptospira)

Question 11

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

Answer 11

Common cold, flu, pneumoan, tuberculosis, measles

Question 12

What pathogens cause gastroenteritis?

Answer 12

Campylobacter
Salmonella enterica/typhi
Some E.coli

Question 13

What pathogen can cause dysentery?

Answer 13

Shigella

Question 14

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

Answer 14

Hepatitis A

Question 15

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

Answer 15

E.coli (urninary)
Candida infections (thrush)

Question 16

How can some pathogens gain access through unbroken skin?

Answer 16

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

Question 17

What are two vectors for pathogens?

Answer 17

Insects

Formites (medical instruments etc.)

Question 18

What is infectious doese?

Answer 18

Numer of microorganisms required to cause disease

Question 19

How is virulence expressed quantitatively?

Answer 19

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

Question 20

What surface molecules do pathogens produce to adhere to surfaces?

Answer 20

Adhesins

Question 21

Where are adhesins usually found?

Answer 21

Fimbria/pilli, which bind specifically to cell surface receptors

Question 22

What type of molecule are most adhesins?

Answer 22

Glycoproteins or lipoproteins

Question 23

What do some pathogens do to the cell surface?

Answer 23

Modify it

Question 24

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

Answer 24

Inject a protein into cells which then acts as a receptor

Question 25

What % of human infections could be caused by biofilms?

Answer 25

Up to 65%

Question 26

Name 4 biofilm associated infections

Answer 26

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

Question 27

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

Answer 27

M protein

Question 28

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

Answer 28

Opa protein

Question 29

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

Answer 29

Mycolic acid

Question 30

What is the primary antibody defence of mucosa?

Answer 30

IgA

Question 31

How do pathogens overcome IgA?

Answer 31

Produce IgA protease

Question 32

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

Answer 32

Produce superoxide dimutase and catalase

Question 33

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

Answer 33

Antigenic variation

Question 34

Give 3 pathogens that show antigenic variation.

Answer 34

Neisseria gonorrhoeae (different opa genes) Influenza virus Trypanosoma brucei

Question 35

What is the difference between antigenic shift and antigenic drift?

Answer 35

Shift is 2 strains combining | Drift is changing/evolving

Question 36

What do bacteria produce to take up host iron?

Answer 36

Siderophores

Question 37

What enzume coagulates fibrin to protect pathogen from phagocytosis?

Answer 37

Coagulase

Question 38

What do kinases do?

Answer 38

Digest fibrin clots

Question 39

What are spreading factors?

Answer 39

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

Question 40

What is the intracellular cement of connective tissue?

Answer 40

Hyaluronic acid

Question 41

What spreading factor breaks down hyaluronic acid?

Answer 41

Hyaluronidase

Question 42

What breaks down collagen?

Answer 42

Collagenase

Question 43

Other then hyaluronidase and collagenase, name other spreading factors

Answer 43

Proteases, nucleases, phospholipases

Question 44

What bacteria produce hyaluronidase?

Answer 44

Streptococcus spp, staphyloccous aureus, certain Clostridium spp

Question 45

What pathogens produce collagenase?

Answer 45

Certain Clostridium spp (Gas gangrene)

Question 46

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

Answer 46

Invasins

Question 47

What is the primary mechanism of host damage?

Answer 47

Toxins

Question 48

What are the two main types of toxin?

Answer 48

Endo and exo

Question 49

Whats the difference between endo and exo toxins?

Answer 49

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

Question 50

What type of molecule are exotoxins?

Answer 50

Proteins

Question 51

What do exotoxins do?

Answer 51

Destroy parts of host's cell or inhibit essential functions

Question 52

What amount of exotoxin is needed?

Answer 52

Low amounts

Question 53

How do exotoxins move around the body?

Answer 53

Soluble in body fluids

Question 54

What does the body produce in response to exotoxins?

Answer 54

Antitoxins (antibodies)

Question 55

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

Answer 55

Heat inactivation

Question 56

What are inactive exotoxins called and where are they used?

Answer 56

Toxoids | Vaccines

Question 57

Name two vaccines with toxoids

Answer 57

Diptheria and tetanus vaccine

Question 58

What are the three main types of exotoxin?

Answer 58

A-B toxins Membrane disrupting toxins Superantigens

Question 59

Name an A-B toxin

Answer 59

Diptheria toxin

Question 60

Name a membrane disrupting toxin

Answer 60

Clostridium perfringens toxin

Question 61

Name a super antigen

Answer 61

Staphlococcal toxic shock toxin

Question 62

How do A-B toxins work?

Answer 62

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

Question 63

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

Answer 63

Inhibits protein synthesis

Question 64

What does the B part of the Shiga toxin do?

Answer 64

Binds to host cell glycolipid in large intestine and kidney

Question 65

What does the A part of the shiga toxin do?

Answer 65

Internalised by receptor mediated endocytosis, inactivates rRNA subunit

Question 66

What does A-B endotoxins of diptheria do?

Answer 66

Inhibit protein synthesis in heart muscle and other cells

Question 67

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

Answer 67

Affect neuromuscular junctions by blocking release of inhibitory neurotransmitters

Question 68

What do botulim A-B endotoxins do?

Answer 68

Affect neuromuscular junctions, prevents release of acetyl choline

Question 69

What toxin damages membrane using enzymes?

Answer 69

C. perfringens toxin

Question 70

What toxin can form pores in host cell membranes?

Answer 70

Streptococcus pneumoniae pneumolysin

Question 71

What do superantigens provoke?

Answer 71

Intense immune response

Question 72

How do superantigens provoke an intense immune response?

Answer 72

Proliferation of T cells

Question 73

What does proliferation of T cells do?

Answer 73

Release excessive amounts of cytokines which damage host

Question 74

Give an example of a superantigen

Answer 74

Staphloccus aureus enteroxins: causes toxic shock syndrome

Question 75

What is an endotoxin?

Answer 75

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

Question 76

How do endotoxins cause fever (pyrogenic response)?

Answer 76

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

Question 77

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

Answer 77

Rabies virus attachment site resembles acetylcholine

Question 78

How does HIV bind to cells?

Answer 78

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

Question 79

How do viruses effect appearance of host cells?

Answer 79

Lysis Appearance of inclusion body Syncitium formation

Question 80

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

Answer 80

Cytopathic effect

Question 81

Round worm causes

Answer 81

elephantitis

Question 82

How does round worm cause elephantitis?

Answer 82

Blocks lymphatic circulation- lymph accumulates causing swelling

Question 83

What algae produces neurotoxins

Answer 83

Alexandrium (produces saxitoxin)