The Human Microbiome

Question 1

Define “Commensal Bacteria”

Answer 1

Bacteria living in a relationship in which one organism derives food or other benefits from host without hurting / helping it

Question 2

Define “Dysbiosis”

Answer 2

Microbial imbalance or mal-adaptation

Question 3

Define “Pro-biotic”

Answer 3

Living non-pathogenic organisms used as food ingredients to benefit the hosts’ health

Question 4

Define “Pre-biotic”

Answer 4

Food ingredient that beneficially affects the host by selectively stimulating the growth of bacteria in the colon

Question 5

How do tears help prevent infection?

Answer 5

Lysozyme dissolves bacterial cell walls

Question 6

How might Intestinal Microbiota directly prevent colonisation of pathogens? Expand on point for each

Answer 6

Competition for nutrients such as sialic acid and fructose

Cause direct toxicity by Bacteriocins and Type VI secretions

Question 7

How might Intestinal Microbiota indirectly prevent colonisation of pathogens? Expand on point for each?

Answer 7

Induce an immune response, such as defensins

Produce metabolic products such as bile salts

Question 8

Is Clostridium difficile Gram positive or Gram negative?

Answer 8

Gram positive

Question 9

How is C. diff spread?

Answer 9

Faeco-oral route

Question 10

ABX associated diarrhoea caused by C. diff refers to what condition?

Answer 10

Pseudomembraneous colitis

Question 11

Describe how Microbiome metabolites usually control C. diff sporulation, and what effect ABX use has on this process

Answer 11

1. Primary bile salts facilitate C. diff to germinate from spores to vegetative bacteria
2. However, primary bile salts are converted into secondary bile salts by normal microflora
3. Secondary bile salts inhibit vegetative C. diff to grow any further, leading to no toxin production
4. ABX use prevents conversion of primary bile salts to secondary bile salts, leading to C. diff vegetative growth and toxin production