Gastroenteritis

Question 1

What is the estimated metabolic capacity of the normal flora of the gut?

Answer 1

That of the liver

Question 2

What are example metabolic functions of the commensal flora of the gut?

Answer 2

Produce B12 and VitK

Question 3

What are other functions of the gut microflora?

Answer 3

Antibody induction, colonisation resistance

Question 4

What type of bacteria mostly inhabit the gut?

Answer 4

Obligate or facultative anaerobes

Question 5

Give examples of commensal gut bacteria.

Answer 5

• Bacteroides sp. (Anaerobic GNB)
• Clostridium perfringens (Anaerobic GPB)
• Escherichia coli (Facultative GNB)
• Enterococcus faecalis (Facultative GPC)

Question 6

What are the common bacterial causes of gastroenteritis?

Answer 6

• Salmonella,
• Shigella,
• E coli
• Campylobacter
• Vibrio cholerae
• Clostridium difficile
• Staph aureus
• Bacillus cereus

Question 7

What are the common viral causes of gastroenteritis?

Answer 7

• Norovirus

- Rotavirus

Question 8

What are the common parasitic causes of gastroenteritis?

Answer 8

• Entamoeba hist.
• Giardia lamblia
• Cryptosporidium

Question 9

What are the clinical features of infective gastroenteritis?

Answer 9

• Acute onset
• Vomiting and/or
• Diarrhoea – frequency, mucous, blood
• Abdominal pain
• Systemic effects – fever etc.

Question 10

What are the possible complications of infective gastroenteritis?

Answer 10

• Dehydration
• Renal failure
• HUS
• Toxic megacolon
• GBS
• Salmonella

Question 11

What investigations should be performed for gastroenteritis?

Answer 11

• Bloods – FBC, U&E, CRP, blood cultures
• AXR – if severe
• Stool
  
  • Ova, parasites and cysts ‘OCP’
  • Microscopy, culture and sensitivity ‘MC&S’
  • Clostridium difficile toxin ‘CDT’
  • Viral PCR

Question 12

What is the main and problematic route of spread of viral gastroenteritis?

Answer 12

Aerosol

Question 13

What was the source of the largest outbreak of foodborne Cryptosporidium?

Answer 13

Bagged salads.

Question 14

Which bacteria produce enterotoxins?

Answer 14

• Vibrio cholerae
• Escherichia coil (entertoxigenic – ETEC, verotoxigenic - - VTEC)
• Clostridium perfringens
• Staphylococcus aureus
• Bacillus cereus
• Clostridium difficile

Question 15

Which bacteria adhere to the bowel wall?

Answer 15

• Shigella sonnei / flexneri
• Escherichia coil (entertoadherent – EAEC)
• Campylobacter jejuni
• Salmonellae

Question 16

What virulence factor is produced by E. Coli O157 and what does it cause?

Answer 16

Shiga-like toxin - causes haemolytic uraemia syndrome

Question 17

What is the mechanism of action of Shiga-like toxin?

Answer 17

Toxin activates G protein leading to increased levels of cAMP. Activates ion channels. Overexcrete Chloride ions. Water follows out of cells into bowel. Different toxins have different mechanisms of action but often diarrhoea is caused by an efflux of K or Cl ions, and the resulting water loss by osmosis.
This means that killing bacteria can actually release more toxin, making disease WORSE.

Question 18

What is the difference between typhoidal and non-typhoidal Salmonella?

Answer 18

Typhoidal has the ability to dissemnate throughout the body.

Question 19

Why should antibiotics generally be avoided in bacterial gastroenteritis?

Answer 19

Killing bacteria will cause the mass release of pathogenic toxins -> can make the disease much worse.
Can increase the duration of the infection.

Question 20

What treatment should be given in bacterial gastroenteritis?

Answer 20

Usually supportive treatment and symptomatic relief.

Question 21

What is the cause of antibiotic-associated diarrhoea?

Answer 21

• Disruption of gut microflora
• Change in metabolism (carbohydrates / bile acids)
• Overgrowth of pathogenic organisms

Question 22

What are the symptoms of antibiotic-associated diarrhoea?

Answer 22

Symptoms range from mild diarrhoea to pseudomembranous colitis, toxic megacolon, perforation, shock

Question 23

Aside from the most common organism, C. difficile, what other organisms can cause antibiotic-associated diarrhoea?

Answer 23

• C. perfringens
• S, aureas
• Candida spp.
• Klebsiella spp.
• Salmonella spp.

Question 24

What is the current treatment for C.diff-associated diarrhoea?

Answer 24

• Oral metronidazole / oral vancomycin
• Both affect gut flora (anaerobes)
• Vancomycin and metronidazole use is a risk factor for VRE selection
• Potential for emergence of resistance to vancomycin / metronidazole in C. difficile

Question 25

What new drug treatment can be given for C. diff?

Answer 25

Oral fidaxomicin

Question 26

What newly emerging, alternative treatment for C.diff has shown considerable success in recent years?

Answer 26

Faecal transplant