Session 9 - Microbiology Of The GI Tract

Question 1

What are some of the beneficial roles of normal flora in the GI tract?

Answer 1

• Synthesise + Excrete Vitamins
• Prevent colonisation by pathogens
• Kill non-indigenous bacteria
• Stimulate development of GALT
• Stimulate production of normal antibodies

Question 2

What are facultative anaerobes?

And give an example of one?

Answer 2

Organisms that prefer oxygen but can live without it.

E.g. E.coli, Staphylococcus

Question 3

Which regions of the GI tract are anaerobic?

Answer 3

• Parts of the mouth (tongue, deep in tastebuds, between teeth)
• Small Bowel
• Colon

Question 4

What are some of the bacteria that are usually present in the mouth?

Answer 4

• Streptococci
• Staphylococci
• Candida
• Lactobacillus
• Enterococcus

Question 5

Where might we do a screening swab for MRSA?

Answer 5

• Nose
• Throat
• Perineum

Question 6

Which bacteria are in 100% of people’s throats?

Answer 6

• Streptococcus Viridans
• Staphylococci
• Neiseria Meningitidis

Question 7

Which bacteria are always present in the colon?

Answer 7

• Bacteroides (Fragillis, Oralis, Melaninogenicus)
• E.coli
• Enterococcus Faecalis

Question 8

In small bowel surgery, why do we need to give prophylactic antibiotics and which one do we normally give and why this one?

Answer 8

• It is considered dirty surgery with a high risk of infection
• Metronidazole is given as it kills anaerobes with Gentamicin or Cephalosporin as these are broad-spectrum antibiotics

Question 9

What is the purpose of Lactobacillus as vaginal flora?

Answer 9

• It converts glycogen -> lactic acid
• Creates acidic environment to prevent other bacterial growth
• especially Candida Albicans (thrush)

Question 10

What are the most common organisms which may cause Gastroenteritis (food poisoning)?

Answer 10

• Salmonella
• Campylobacter
• Listeria
• Also may have toxins from Staph + Clostridium

Question 11

Describe cholera

Causative organsim, pathogenesis, symptoms, treatment

Answer 11

• Vibrio Cholerae
• Causes massive salt and hence water movement into lumen of GI tract
• Causes “Rice-water” diarrhoea and severe dehydration
• Treat with Oral Rehydration Therapy

Question 12

Give two differences between bacteraemia and septicaemia

Answer 12

• There are no symptoms in bacteraemia, there are in septicaemia
• In septicaemia the bacteria have not been removed from the bloodstream but in bacteraemia they are rapidly removed

Question 13

What is the usual causative organism for Traveller’s Diarrhoea?

Answer 13

Enterotoxinogenic E.coli