How do micro-organisms cause disease

Question 1

Common symptoms of infection

Answer 1

Diarrhoea
Cancer
Anaemia
Blood loss
Fever

Question 2

What is diarrhoea caused by?

Answer 2

Disruption of gut flora, caused by clostridium difficile

Question 3

What is an infection?

Answer 3

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

Question 4

What is colonisation?

Answer 4

Microbes living in host without causing injury

Question 5

What is a protist?

Answer 5

Eukaryote that isn’t an animal, plant or fungi

Question 6

What is a protozoa?

Answer 6

Protist that isn’t photosynthetic

Question 7

What is a local infection?

Answer 7

Confined to small part of body near site of entry

Question 8

What is a focal infection?

Answer 8

Pathogen spreads to secondary location

Question 9

What is a systemic infection?

Answer 9

Pathogen disseminated throughout body

Question 10

What is a pathogen?

Answer 10

Microorganism that causes disease

Question 11

What is pathogenicity?

Answer 11

Ability of an organism to cause disease

Question 12

What is virulence?

Answer 12

Degree of disease caused by organism

Question 13

What are virulence factors?

Answer 13

Molecules produced by organism that make replication in host more effective

Question 14

What is the ID50 value?

Answer 14

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

Question 15

Which bacteria can’t survive outside host?

Answer 15

Sexually transmitted

Question 16

Why is clostridium difficile difficult to kill?

Answer 16

Its spores are resistant to alcohol hand gel

Question 17

How do you kill clostridium difficile?

Answer 17

Physically removed with soap and water

Hydrogen peroxide fogging can also be used

Question 18

What is a biofilm?

Answer 18

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

Question 19

Why is pseudomonas aeruginosa dangerous?

Answer 19

Forms biofilms in tap assemblies - compromises hand washing

Question 20

How do rod shaped bacteria move?

Answer 20

Flagella

Question 21

What are flagella?

Answer 21

Filamentous protein structures with a motor in the plasma surface

Question 22

Function of adhesin

Answer 22

Protein/glycoprotein that attaches to host cell receptors

Conveys host cell and tissue specificity

Question 23

With which molecules is adhesin expressed?

Answer 23

Fimbrae/pilli
Flagella
Cilia

Question 24

How does enterotoxin e.coli use adhesion factors?

Answer 24

Expresses type 1 fimbrae to adhere to intestinal epithelial cells

Question 25

What are exotoxins?

Answer 25

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

Question 26

What are endotoxins?

Answer 26

Part of bacterium wall and only released when microbe destroyed

Question 27

What type of toxin is clostridium botulinum toxin?

Answer 27

Exotoxin

Question 28

What does clostridium botulinum toxin do?

Answer 28

Inhibits release of acetylcholine from neurone, causing paralysis

Question 29

What disease does streptococcus pyogenes cause?

Answer 29

Strep throat

Question 30

What disease does streptococcus mutant cause?

Answer 30

Dental caries

Question 31

What disease does Neisseria gonorrhoeae cause?

Answer 31

Gonorrhoea

Question 32

Which type of toxin is the cholera toxin?

Answer 32

Exotoxin

Question 33

Symptoms of cholera

Answer 33

Severe watery diarrhoea

Question 34

How does cholera result in diarrhoea?

Answer 34

- 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

Question 35

What does the cholera toxin phage do?

Answer 35

Carries cholera toxin gene and other virulence factors

Question 36

How is toxic shock syndrome caused?

Answer 36

Incorrectly used tampons and blocking nasal passage

Question 37

What is TSS caused by?

Answer 37

Streptococcus progenies and staphylococcus aureus

Question 38

What is TSS?

Answer 38

- 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

Question 39

When are endotoxins produced?

Answer 39

When bacteria die

Question 40

What does a high concentration of endotoxins result in?

Answer 40

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

Question 41

What does a low concentration of endotoxins result in?

Answer 41

Inflammatory response for defence

Question 42

What are the three components of LPS?

Answer 42

O-antigen/polysaccharide, core oligosaccaride and lipid A

Question 43

Which pathogens produce hyaluronidase?

Answer 43

Staphylococcus aureus, streptococcus pyogenes and clostridium perfringens

Question 44

What does hyaluronidase do?

Answer 44

Degrades hyaluronic acid and opens cell junctions between connective tissues

Question 45

What is amoebic colitis?

Answer 45

Inflammation of colon

Question 46

How does entamoeba histolytic kill?

Answer 46

- 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

Question 47

How do capsules resist the body's defences?

Answer 47

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

Question 48

How do pathogens fight antibodies?

Answer 48

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

Question 49

How does the TB bacterium survive endocytosis?

Answer 49

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

Question 50

What is antigenic variation?

Answer 50

- 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)

Question 51

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

Answer 51

Moves from liver to RBCs where it multiplies and bursts out

Question 52

Why do RBCs infected with plasmodium appear knobbly?

Answer 52

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

Question 53

Which pathogen causes immune mediated post-streptococcal glomerulonephritis?

Answer 53

Streptococcus pyogenes

Question 54

What is a super-antigen?

Answer 54

Cross links between T cells and antigen presenting cells

Question 55

What is immune mediated post-streptococcal glomerulonephritis?

Answer 55

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