Infections

Question 1

Describe the defenses of the GI tract. (5)

Answer 1

Saliva - antibacterial enzymes
Stomach acid - kills most bacteria
Small intestines - bile kills lots of bacteria. 
Colonic mucus
Anaerobic environment

Question 2

Describe the benefits of gut microbiota (4)

Answer 2

Harmful bacteria are outcompetes for nutrients
Produces antimicrobial substances
Produces nutrients like vit K
Birth canal kickstarts the gut microbiome in neonates.

Question 3

Explain the benefits of the microbiota producing short chain fatty acids. (3)

Answer 3

Butyrate - energy source for colonocytes
Acetate - involved in cholesterol metabolism
Propionate - regulates satiety

Question 4

Describe some of the relationships between general health and microbiota. (4)

Answer 4

Obesity and IBD decrease diversity of microbiota

Microbiota affect the way the body responds to insulin and chemotherapy.

Question 5

Describe some things that can disrupt the natural gut biome. (4)

Answer 5

Sweetness
Unnecessary gluten free diets
PPIs
Antibiotics

Question 6

Describe a faecal microbiota transplant. (3)

Answer 6

Feeding people poop to supply the good microbiota.

Drastic help in C diff and Crohn’s.

Question 7

Describe salmonella infection. (6)

Answer 7

Gram negative rod
Nausea, vomiting, non-bloody diarrhoea, fever, cramping.
Self limiting in 2-3 days
Access enterocytes > moves to submucosa > encounters macrophages > moves to RES > lymphoid hyperplasia > re-enters gut through liver.

Question 8

Describe campylobacter infection. (7)

Answer 8

Gram negative, spiral shaped rod
Fever, cramping, possibly bloody diarrhoea
Self limiting in 7-14 days, or with abx if bloody
Releases a cytotoxin like cholera.

Question 9

Describe shigella infection. (6)

Answer 9

Gram negative rod
Definitely bloody diarrhoea
Causes shigellosis - dysentery common in young children
Self limiting in about 7 days
Invades colonocytes and spreads to surrounding cells causing abscesses.

Question 10

Describe enterotoxigenic E. Coli infection. (5)

Answer 10

Gram positive rod
Travellers (non-bloody diarrhoea)
Self limiting in 2-3 days
Hypersecretion of Cl- into lumen.

Question 11

Describe Clostridium difficile infection. (5)

Answer 11

Gram positive, spore forming rod.
Non-bloody diarrhoea, often hospital acquired or following abx therapy.
Treat with metronidazole / vancomycin and probiotics.

Question 12

Describe rotavirus infection. (4)

Answer 12

Common in under 5s because you can only get it once.
Vomiting, fever, diarrhoea lasting up to a week.
Chloride secretion, brush border enzyme function.

Question 13

Describe norovirus infection. (4)

Answer 13

So many strains, can get it repeatedly.
Vomiting, fever, watery diarrhoea
Self limiting in 1-3 days.
Cl- secretion, brush border dysfunction.

Question 14

Describe cryptosporidium infection. (5)

Answer 14

Protozoa
Caught from animals, other humans or bodies of water - ingestion of an oocyst.
Watery diarrhoea
Cl- secretion, brush border dysfunction

Question 15

Describe Giardia infection. (7)

Answer 15

Flagellate Protozoa
Often asymptomatic for 10 days then symptoms lasting 6 weeks.
Diarrhoea and cramping
Cyst ingestion causing villus atrophy in the small intestine.
Treat with abx
Post giardia lactose intolerance is common.

Question 16

Describe entamoeba histolytica infection. (7)

Answer 16

Amoeba
Often asymptomatic but could be bloody diarrhoea and inflammation similar to IBD.
Ingestion of cysts
Treat with anti-protozoals and metronidazole.
Severe symptoms of toxic megacolon or colitis may require surgery.