Gastroenteritis

Question 1

What are the most common commensal bacteria type in the gut?

Answer 1

Obligate anaerobes

Outnumber facultative anaerobic by 100 to one

Question 2

What are the ebenficial effects of commensal bacteria in the guy>

Answer 2

metabolism
Colonisation resistance
Antibody induction

Question 3

What are the main commensal bacteria in the gut?

Answer 3

• Bactericides sp
• Clostridium perfringens
• E coli
• Enterococcus faecalis

Question 4

What are the key bacterial causes of gastroenteritis?

Answer 4

• Salmonella
• E coli
• C Diff
• Shigella
• V Cholerae
• Staph aureus
• Bacillus cereus

Question 5

What are the main causes of gastroenteritis outbreaks in UK?

Answer 5

Foodbourne infections e.g. salmonella

Recreational water, e.g. swimming pools

Animal contact

Question 6

What are the clinical presentation of gastroenteritis?

Answer 6

• Acute onset
• Vomiting and diarrhoea (freq, mucous, bloody)
• systemic effects e.g. fever
• Abdo pain
• Complications e.g. dehydration, renal failure, salmonella, toxic megacolon etc

Question 7

What investigations are carried out in gastroenteritis?

Answer 7

Blood - FBC, U&E, CPR, cultures

- Stools - parasite/oocytes, microscopy, toxin e.g. C diff toxin, PCR - virus

Question 8

Why are investigations in gastroenteritis difficult?

Answer 8

So many commensal bacteria, difficult to tease out causative bacteria

Question 9

Whats the most common cause of viral gastroenteritis?

Answer 9

Norovirus

Question 10

Why is norovirus a very successful pathogen?

Answer 10

Low infective dose, last on surfaces for long time, long excretion (faecal/oral route)

Question 11

How is viral gastroenteritis spread?

Answer 11

Aerosols - vomiting and diarrhoea

Question 12

What are the main parasites that cause gastroenteritis?

Answer 12

Cryptosporidium
Giardia
Entamoeba

Question 13

How is cryptosporidium transmitted mostly and what adaptation does it have which makes it very resistant

Answer 13

Waterborne

Oocyte - resists chlorine

Question 14

What are the two main routes by which bacteria cause infection?

Answer 14

Production of toxin

Adhesion/invasion of cell

Question 15

What is the name for E. coli 0157?

Answer 15

Enterohaemorrhagic Ecoli

Question 16

How does E coli 0157 cause symptoms?

Answer 16

TOXIN - Shiga toxin

Question 17

Why is E coli 0157 particularly dangerous?

Answer 17

Can cause haemolytic uraemic syndrome (HUS) - can cause renal failure

Question 18

What is the mechanism by which E coli causes diarrhoea?

Answer 18

Activates G protein which increase cAMP levels. This activates ion channels which causes an increased efflux of Cl ion. Osmotic gradient produced - diarrhoea/dehydration

Question 19

How does salmonella cause infection?

Answer 19

Causes infection ITSELF (not toxin)

Question 20

How is gastroenteritis treated?

Answer 20

Antibiotics avoided (wait it out/rehydration) can worsen symptoms/prolong carriage

Question 21

How does antibiotic associated diarrhoea occur?

Answer 21

Disrupt normal microflora

• change in metabolism (CHO/bile acid)
• overgrowth of pathogenic bacteria

Question 22

What conditions can antibiotic cause?

Answer 22

Diarrhoea
Pseudomembranous colitis 
Toxic megacolon
Perforation
Septic shock

Question 23

What is the main cause of pseudomembranous colitis?

Answer 23

C. Diff

Question 24

What C diff strain is associated with deaths in younger individuals

Answer 24

CD027

Question 25

What antibiotics are more associated with C diff infection?

Answer 25

4 C’s
-ciprofloxacin (quinolones)

co-amoxiclav (broad spectrum penicllins,)

clindamycin

cephalosporins (3rd generation).

Fluroquinolones (CD027 strain)

Question 26

What are the main antibiotics used for C. Diff?

Answer 26

Oral Metronidazole/

Vancomycin

Question 27

Whats the best ‘cure’ for C diff?

Answer 27

Faecal transplants - restores commensal gut flora