4.1- GI Infections

Question 1

Define Gastroenteritis

Answer 1

Inflammation of the mucous membrane of both the stomach and intestine, usually causing nausea, vomiting and diarrhoea

Question 2

Name some common symptoms of gastroenteritis

Answer 2

diarrhoea
vomiting
nausea
abdominal discomfort

Question 3

What does acute gastroenteritis present with

Answer 3

causes PROFUSE WATERY DIARRHOEA, often causing nausea and vomiting but without localised findings

between cramps the abdomen is completely relaxed

Question 4

What are the two main causes of infectious gastroenteritis?

Answer 4

1) Pre-formed toxins eg food poisoning

2) Living organisms- eg helminths, virus, bacteria

Question 5

Which 3 classes of Helminths cause GI Infections? (NCT)

Answer 5

NEMATODES: round bodied worms
eg roundworms, pinworms, hookworms, whipworms

CESTODES: flat-bodied worms that are segmented
eg tapeworms

TREMATODES: flat-bodied worms that are non-segmented
eg flukes

Question 6

What are hookworms?

Answer 6

• have the ability to grasp onto epithelium
• found in contaminated food
• can burn through skin and cause red worm appearance

Question 7

What is Ascaris?

Answer 7

giant intestinal roundworm

• found in contaminated meat/ soil
• blockages cause acute abdominal pain

Question 8

What is enterobiasis

Answer 8

pinworms

-seen in young children
affects 50% of primary school children in the UK

Question 9

How do pinworms lay their eggs?

Answer 9

• ingestion of egg
• egg travels through intestine and finds hospitable environment
• at night, the female pinworm will travel out from the anus and lay eggs in the anus bc it is a moist and wet region
• has a mild reaction with the sticky substance it lays its eggs in and causes white appearance on anus and scratching

Question 10

What are some signs of pinworm infection?

Answer 10

• visible detection of pinworms in faeces
• malaise
• anorexia
• dark circles

Question 11

What is the body’s defence against pinworms?

Answer 11

Eosinophils ( granulocytes)

defence against parasitic worms

-have chemical compounds within them that are directed directly towards the nervous system of pinworms

Question 12

What is Trichuris Trichiura?

Answer 12

whipworm

similar mechanism to pinworms but bigger

• infection causes prolapse of anus
• causes soreness and pain

Question 13

What causes Schistosomiasis?

Answer 13

• tropical disease
• parasitic worm; comes in both male and female forms
• uses snails an an intermediate host, but can also use dogs or rats

-engulfed in soil by humans

Question 14

How does schistosomiasis present in humans?

Answer 14

• engulfed in soil by humans
• causes a rash
• leads to swollen abdomen and increased vascularisation

Question 15

What is a tapeworm?

Answer 15

a type of CESTODE or flat bodied worm that is segmented

-eats intestines and depletes humans of nutrients
ie causes weight loss
-seen via ingestion of meat which contains ingestion cysts eg pork

Question 16

Define food poisoning

Answer 16

any illness resulting from the consumption of food

Question 17

Define food infection

Answer 17

presence of bacteria or other microbes which infect the body after consumption

Question 18

Define food intoxication

Answer 18

ingestion of toxins contained within the food

Question 19

What bacteria causes food poisoning?

Answer 19

Staph aureus

-main cause of food poisoning

Question 20

How does staph aureus cause food poisoning?

Answer 20

• produces enterotoxin
• has the ability to change its genes quickly; can switch/ turn on genes responsible for producing the enterotoxins
• you need less than 1 microgram of toxin to cause disease

Question 21

How does the enterotoxin affect the gut?

Answer 21

• enterotoxin itself will use goblet cells and epithelial cells as passage through the gut mucosa
• enters lamina propria and causes immune response
• this causes an increase in 5-HT
• 5-HT will act on Vagus Nerve+ will act signal to the rest of the body and the nervous system and the stomach
• produces vomiting effect

Question 22

What could vomiting cause?

Answer 22

could cause

• metabolic alkalosis
• loss of HCl

Question 23

What causes an inflammatory response in the intestines?

Answer 23

-disrupts passage of substances through epithelium
-this causes a change in epithelium and then watery diarrhoea
could cause:
- hypokalaemia
-reduced HCO3-
- more metabolic acidosis

Question 24

How does S. aureus cause poisoning and illness?

Answer 24

• caused by Staph enterotoxin
• relatively mild+ from only a few hours to 1 day.
• not contagious
• onset of symptoms is usually rapid (1 to 6 hours)

Question 25

What are some symptoms of S aureus poisoning?

Answer 25

• nausea
• abdominal cramping
• vomiting
• diarrhoea

Question 26

What is Clostridium Perfringes?

Answer 26

• spore forming
• anaerobic
• one of the causes of food poisoning

Question 27

How does Clostridium Perfringes cause damage to the cell?

Answer 27

once ingested, produces a toxin

• toxin goes through natural protective layer of human macrobiotica ie biofilm
• toxin crosses epithelia and lamina propria and produces an immune response
• immune response weakens epithelial cells and makes them more prone to invasion of CP and replication
• therefore more bacteria produced and more toxins produced causing more inflammation
• this breaks down epithelial structure, leading to poor passage of ions, water enters lumen causing WATERY DIARRHOEA

Question 28

What is bacillus cereus?

Answer 28

-gram positive
-rod shaped, facultative anaerobic bacterium and belong to bacillus genus
-found in rice; food poisoning
because of reheating takeaway rice

Question 29

How does bacillus cereus cause disease?

Answer 29

-cause emetic and diarrhoeal disease

Question 30

How does bacillus cereus cause EMETIC DISEASE?

Answer 30

-consumed from cooked rice or other starchy foods left at room temperature for a prolonged time

Question 31

How does bacillus cereus cause DIARRHOEAL DISEASE?

Answer 31

consumed from meat and ready prepared meals that were improperly stored, causes diarrhoea and stomach cramps

Question 32

How do viruses use biofilm in gut to aid their function?

Answer 32

• use them as cofactors to hide them and stabilise them
• poor gut flora health= higher susceptibility to infection
• attach to LPS in gut microbiotica and use them as cofactors to help them hide within them and stabilise them.

Question 33

How does viral gastroenteritis occur?

Answer 33

• common cause of infectious diarrhoea
• infects epithelium of intestine
• watery diarrhoea
• WBC’s and visible blood are rare

Question 34

What are the 4 categories of viral gastroenteritis? (RCAE)

Answer 34

Rotavirus
Claicivirus (norovirus)
Astrovirus
Enteric Adenovirus

Question 35

What is the calcivirus?

Answer 35

norovirus

• RNA virus
• ingestion of infected food/water leads to local infection and inflammation in proximal small intestine.
• projectile vomiting (up to 7m long)
• resistant virus so needs a v strong bleach to disinfect it

Question 36

What is the rotavirus?

Answer 36

• RNA virus
• most common cause of diarrhoea in young children
• DS segmented
• highly contagious; feral-oral
• incubation 1-3 days, lasts 4-8 days

Question 37

How does rotavirus infect humans?

Answer 37

• infects villus of the proximal small intestine
• replicates with and lyses cells
• impaired absorption of carbs and nutrients
• vomiting followed by diarrhoea, as virus leaves cells and epithelium bc epithelium is disrupted; death and vomiting
• dehydration and hospitalisation common in young children

Question 38

How do you diagnose rotavirus?

Answer 38

EIA antigen in stool

Question 39

How do you treat rotavirus?

Answer 39

oral rehydration or IV

controversial But oral vaccine now available