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Immune and lymphatic system > How do micro-organisms cause disease > Flashcards

How do micro-organisms cause disease Flashcards

1
Q

Common symptoms of infection

A 
Diarrhoea
Cancer
Anaemia
Blood loss
Fever
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2
Q

What is diarrhoea caused by?

A

Disruption of gut flora, caused by clostridium difficile

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3
Q

What is an infection?

A

Invasion and multiplication of microbes in the host’s tissues that lead to cellular injury as a result of their multiplication, production of toxins, immune response or competition in metabolism

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4
Q

What is colonisation?

A

Microbes living in host without causing injury

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5
Q

What is a protist?

A

Eukaryote that isn’t an animal, plant or fungi

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6
Q

What is a protozoa?

A

Protist that isn’t photosynthetic

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7
Q

What is a local infection?

A

Confined to small part of body near site of entry

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8
Q

What is a focal infection?

A

Pathogen spreads to secondary location

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9
Q

What is a systemic infection?

A

Pathogen disseminated throughout body

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10
Q

What is a pathogen?

A

Microorganism that causes disease

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11
Q

What is pathogenicity?

A

Ability of an organism to cause disease

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12
Q

What is virulence?

A

Degree of disease caused by organism

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13
Q

What are virulence factors?

A

Molecules produced by organism that make replication in host more effective

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14
Q

What is the ID50 value?

A

Number of microorganisms required to cause infection in 50% of inoculated animals

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15
Q

Which bacteria can’t survive outside host?

A

Sexually transmitted

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16
Q

Why is clostridium difficile difficult to kill?

A

Its spores are resistant to alcohol hand gel

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17
Q

How do you kill clostridium difficile?

A

Physically removed with soap and water

Hydrogen peroxide fogging can also be used

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18
Q

What is a biofilm?

A

Bacterial community attaches to surfaces, e.g. in glycocalyx

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19
Q

Why is pseudomonas aeruginosa dangerous?

A

Forms biofilms in tap assemblies - compromises hand washing

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20
Q

How do rod shaped bacteria move?

A

Flagella

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21
Q

What are flagella?

A

Filamentous protein structures with a motor in the plasma surface

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22
Q

Function of adhesin

A

Protein/glycoprotein that attaches to host cell receptors

Conveys host cell and tissue specificity

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23
Q

With which molecules is adhesin expressed?

A

Fimbrae/pilli
Flagella
Cilia

24
Q

How does enterotoxin e.coli use adhesion factors?

A

Expresses type 1 fimbrae to adhere to intestinal epithelial cells

25
Q

What are exotoxins?

A

Proteins coded for by bacteria which are released once the microbe is alive, often target specific receptors on cell

26
Q

What are endotoxins?

A

Part of bacterium wall and only released when microbe destroyed

27
Q

What type of toxin is clostridium botulinum toxin?

A

Exotoxin

28
Q

What does clostridium botulinum toxin do?

A

Inhibits release of acetylcholine from neurone, causing paralysis

29
Q

What disease does streptococcus pyogenes cause?

A

Strep throat

30
Q

What disease does streptococcus mutant cause?

A

Dental caries

31
Q

What disease does Neisseria gonorrhoeae cause?

A

Gonorrhoea

32
Q

Which type of toxin is the cholera toxin?

A

Exotoxin

33
Q

Symptoms of cholera

A

Severe watery diarrhoea

34
Q

How does cholera result in diarrhoea?

A
  • Activation of adenylate cyclase in intestinal cells
  • Increased levels of CAMP and secretion of fluid and electrolytes out of the cell, causing diarrhea
  • Opens chlorine ion channels
  • Inhibits sodium uptake
35
Q

What does the cholera toxin phage do?

A

Carries cholera toxin gene and other virulence factors

36
Q

How is toxic shock syndrome caused?

A

Incorrectly used tampons and blocking nasal passage

37
Q

What is TSS caused by?

A

Streptococcus progenies and staphylococcus aureus

38
Q

What is TSS?

A
  • Involves production of super-antigens: stimulate T cells non-specifically without normal antigenic recognition
  • Cross link class II MHC on antigen presenting cell and T cell receptor
39
Q

When are endotoxins produced?

A

When bacteria die

40
Q

What does a high concentration of endotoxins result in?

A

Cytokine storm - severe drop in blood pressure with multi-organ failure

41
Q

What does a low concentration of endotoxins result in?

A

Inflammatory response for defence

42
Q

What are the three components of LPS?

A

O-antigen/polysaccharide, core oligosaccaride and lipid A

43
Q

Which pathogens produce hyaluronidase?

A

Staphylococcus aureus, streptococcus pyogenes and clostridium perfringens

44
Q

What does hyaluronidase do?

A

Degrades hyaluronic acid and opens cell junctions between connective tissues

45
Q

What is amoebic colitis?

A

Inflammation of colon

46
Q

How does entamoeba histolytic kill?

A
  • Enters blood stream and reaches liver
  • Adhere to tissue surface
  • Release proteases which begin to degrade tissues
  • Amoebic colitis = inflammation of colon
  • Death caused when reaches liver and/or brain
47
Q

How do capsules resist the body’s defences?

A

Mask immunogenic antigens, impairs complement pathways, impair opsonization and reduce phagocytosis

48
Q

How do pathogens fight antibodies?

A

Produce igA proteases that break up antibodies which would otherwise destroy the pathogen. IgA protects mucosal surfaces

49
Q

How does the TB bacterium survive endocytosis?

A

TB caused by mycobacterium tuberculosis. Starts in alveolar sacs of lungs and replicates in the endosomes of alveolar macrophages

50
Q

What is antigenic variation?

A
  • Change outer antigens so they aren’t recognised
  • Viral mutation (either genetic drift or shift)
  • Repeatedly change appearance by displaying different surface antigens (gene switching)
51
Q

Where does the plasmodium parasite travel to when it enters the body?

A

Moves from liver to RBCs where it multiplies and bursts out

52
Q

Why do RBCs infected with plasmodium appear knobbly?

A

Proteins that bind to the outside of the RBC. This stops it being killed in the liver and spleen. The knobs help the RBCs stick to the walls of the capillaries

53
Q

Which pathogen causes immune mediated post-streptococcal glomerulonephritis?

A

Streptococcus pyogenes

54
Q

What is a super-antigen?

A

Cross links between T cells and antigen presenting cells

55
Q

What is immune mediated post-streptococcal glomerulonephritis?

A

Immune-complex deposits consisting of bacterial antigens including streptococcal pyrogenic exotoxin (a super-antigen) occur elsewhere in body

Immune and lymphatic system (27 decks)

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