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IMED2001 UWA > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

What are the portals of entry for pathogens?

A

Point at which pathogen can enter

3 categories:
mucous membranes
skin
Parenteral routes

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2
Q

Why are mucous membranes considered the route of entry into the body?

A

They are in direct contact with environment

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3
Q

What is the favourite portal of entry for pathogens? Rank in order from favourite to least favourite

A

The respiratory tract (we breathe all day every day)

Gastrointestinal tract

The genitourinary tract (more complicated portal of entry)

Skin and conjunctiva of eye provides impermeable barrier which must be broken to allow entry

Insect bites (vector transport via intermediate)

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4
Q

What happens when pathogens gain access to epidermis?

A

Localised infection

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5
Q

What happens when pathogens gain access to dermis?

A

Systemic infection

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6
Q

When pathogens breach the first barriers of disease how do they establish themselves?

A

They use capsules or fimbriae to attach to the surface of cells or tissues

Can use adhesins to adhere to tissues

They form biofilms

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7
Q

How do plaques form?

A

Pellicle coats tooth and bacteria subsequently adhere. 300 to 400 different types of bacteria will adhere to each other building the biofilm

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8
Q

How do pathogens increase their numbers?

A

Rabid growth (some pathogens double in numbers after 20 minutes)

Binary fission

Viral infection produces millions of viral particles

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9
Q

How do more virulent organisms differ from less virulent organisms in their ability to cause infection?

A

more virulent organisms need less individuals to form an infection in 50% of the host population

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10
Q

What is the difference between active and passive defence mechanisms for pathogen to defeat host defences?

A

Passive defense mechanisms involves using built in structures on pathogen

Active defences involve attacking host defences

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11
Q

How does the capsule protect the bacterium?

A

The capsule keeps surface of engulfing phagocyte from sticking to bacterium and bacterium is more likely to be free.

Some bacteria are phagocytosed but then the capsule protects them in the phagolysosome.and makes them survive in there

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12
Q

How do M proteins increase virulence?

A

They make them adhere better to host cells and can inhibit phagocytosis

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13
Q

Where are M proteins located?

A

In the cell wall of streptococcal organisms

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14
Q

What is mycolic acid?

A

Waxy material found in cell walls of mycobacterium species

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15
Q

How does mycolic acid protect mycobacterium from death?

A

Inhibit phagocytosis and antibiotic entry

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16
Q

What are some active protective strategies?

A

Production of enzymes that affect host defences

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17
Q

Why do bacteria produce extracellular enzymes?

A

Increase protection against host defences

Enable spread by attacking and killing host defensive cells

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18
Q

What do hyaluronidase and collagenase enzymes do?

A

Break down connective tissue and collagen opening up the cell surfaces and allow the bacteria to enter substructures

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19
Q

What do leukocidins do?

A

Destroy white blood cells

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20
Q

What do haemolysins do?

A

Attack red and white blood cells

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21
Q

What do coagulases do?

A

Cause formation of fibrin clots

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22
Q

What do kinases do?

A

Break down fibrin and destroy clots

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23
Q

How can pathogens hide from host defences?

A

Getting inside the host cell

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24
Q

What type of pathogens are viruses?

A

Obligate intracellular parasites that can easily enter host cells

25
Q

How do bacteria survive intracellular environments?

A

They use cytoskeleton (microtubules and microfilaments) to get in and move around host cell

26
Q

What are the causes of damage to host?

A

Occur because of damage by pathogens to host

Damage caused by host trying to defeat infections

27
Q

What is the difference between direct and indirect damage?

A

Direct damage is obvious and includes destruction of host cells. It is usually controlled by host immune response

Indirect damage involves a systemic infection as a result of toxin production by pathogen

28
Q

Describe bacterial toxins:

A

Bacterial toxins are very poisonous

soluble in aqeous solutions

Easily diffusible in blood and can be fatal

29
Q

How do bacterial toxins affect host?

A

They produce common symptoms such as fever shock diarrhoea cardiac and neurological trauma and destruction of blood vessels

30
Q

What are the types of bacterial toxins?

A

Exotoxins and endotoxins

31
Q

What are exotoxins?

A

Specifically secreted toxins that damage the host. They are among the most lethal substances known

32
Q

Are exotoxins water or lipid soluble?

A

Water soluble usually in blood and lymphatic system

33
Q

How is the ability of exotoxins to diffuse?

A

They diffuse rapidly into tissues

34
Q

How are exotoxins typically produced?

A

As proenzymes

35
Q

What are the 3 types of exotoxins?

A

Cytotoxins (kill cells)

Neurotoxins (interfere with neurological signalling)

Enterotoxins (affect lining of digestive system)

36
Q

What is anthrax?

A

Toxin produced by bacillus anthracis

37
Q

How does anthrax affect host?

A

Interrupts signalling capability of host macrophages and dendritic cells

38
Q

Where are the 3 parts of anthrax assembled?

A

Outside the organism cell wall

39
Q

Where are the 3 parts of anthrax produced?

A

Each part is individually produced within the bacillus anthracis bacterium and then secreted where it assembles outside the cell wall

40
Q

How does diphtheria affect host?

A

inhibits protein synthesis in host

41
Q

What bacteria produces diphtheria toxin?

A

Corynebacterium diptheriae

42
Q

How is diphtheria produced?

A

Initially it is in an inactive form and then becomes active

43
Q

What is diphtheria toxin structure like?

A

Contains 2 chains:

A chain which inhibits protein synthesis

B chain which binds to target cell and allows entry

44
Q

How toxic is diphtheria?

A

A single molecule can killa host cell!

45
Q

What is botulinum toxin?

A

Neurotoxin that inhibits acetylcholine

46
Q

How many forms of botulinum toxin are there?

A

7

47
Q

How does Botulinum cause disease?

A

Disrupts neurological signalling of skeletal muscle causing paralysis

48
Q

What bacterium causes tatenus?

A

Clostridium tetani

49
Q

What does tetanus do?

A

Causes loss of skeletal muscle control

Prevents muscle relaxation

Results in uncontrollable convulsive muscle contractions and this is why lockjaw is an early symptom

50
Q

What bacteria causes cholera?

A

Vibrio cholera

51
Q

What is the structure of cholera like?

A

B chain which binds to target cell

A chain causes cell to release lots of electrolytes

52
Q

What is toxic shock syndrome?

A

caused by enterotoxin from staphylococcus aureus

53
Q

What type of toxin is cholera?

A

an enterotoxin

54
Q

What is staphylococcus auries infection associated with?

A

Prolonged super absorbent tampon use

55
Q

How does toxic shock syndrome hurt host?

A

Excessive loss of electrolyte fluids leading to hypotensive shock

56
Q

What are endotoxins?

A

Toxins that are found within gram negative cell walls which are released upon death of bacterium

57
Q

What is the difference between exo and endotoxins?

A

Endotoxins do not cause immune response

58
Q

What is viral host cell damage called?

A

cytopathogenic effect

59
Q

How does CPE of viruses occur?

A

Viral overload

Cytocidal effects (killing host cells)

Non-cytosidal effects (damage caused by host defence)

IMED2001 UWA (44 decks)

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