GI Infections

Question 1

Key organs of the gastrointestinal (GI) tract

Answer 1

Mouth
Stomach
Small intestine
Large intestine

Question 2

Main functions of the GI tract

Answer 2

Absorb nutrients + excretion of waste products
Requires
- breakdown of large molecules
- secretion of enzymes
- transport mechanisms
- secretion of compounds to aid absorption

Question 3

Resident microflora of GI tract

Answer 3

GI tract contains 10^14 bacteria - weighing 1.5kg

• found in the lower GI tract
• GI microbiota includes hundreds of species of bacteria, archea + fungi + bacteriophage
• GI microbiota is dense, symbiotic + complex microbial ecosystem
• Body’s immune system prevents individual species increasing to an extent that it can cause infection

Question 4

Role of GI microbiota

Answer 4

Digest material human enzymes can’t do + handle nutrients
Compete with pathogenic microorganisms
Influences immune system

Question 5

GI tract infections are caused by…

Answer 5

Viruses, bacteria, protozoa +worms

Question 6

Common cause of GI tract infection

Answer 6

Viruses

Question 7

Key routes of entry of pathogens into GI tract

Answer 7

Ingestion of contaminated food or water

Poor hygiene

Question 8

Cause of Peridontal disease

Answer 8

Caused by build up of plaque - a biofilm produced by bacteria

Question 9

Symptoms of Gastroenteritis

Answer 9

Vomiting +/or diarrhoea, pain + cramps

• self-limiting
• does not need treatment (unless severe therefore use of antibiotic needed)

Question 10

Gastroenteritis

Answer 10

Inflammation of GI mucosa - include stomach + duodenum

Question 11

How can you contract Gastroenteritis

Answer 11

Eating contaminated food/water

Person-person contact

Question 12

Common cause of Gastroenteritis + diarrhoeal disease

Answer 12

Campylobacter sp.

Question 13

Campylobacter sp.

Answer 13

Cytochrome oxidase positive
Microaerophilic
Curved gram-negative rod (cockscrew)
- inhabit intestinal tract of food-chain animals
- it can be killed by heat
- treatment = electrolyte replacement + rehydration
- antimicrobial treatment is recommended in invasive cases or to eliminate carrier state

Question 14

Salmonella sp.

Answer 14

Gram-negative, non- lactose fermenting bacteria in enterobacteriaceae family
Large infective doses can cause salmonellosis
Produce Type III secretion system which produces proteins that
- inhibit phagocytosis
- rearrange cytoskeleton of eukaryotic cells
- induce apoptosis of epithelial cell they infect

Question 15

Characterise Salmonellosis

Answer 15

Non-bloody diarrhoea, nausea + vomiting

Question 16

Salmonella typhi causes

Answer 16

Typhoid fever

Question 17

Which Salmonella serotype causes gastroenteritis

Answer 17

S.enterica

Question 18

Shigella

Answer 18

Gram-negative, non-motile bacteria (like E.coli)
Cause dysentery
Small inoculation with Shigella sp. required to cause disease
Easily transmitted + contagious
Produces shiga toxin - stops protein synthesis
Severe cases treated with ciprofloxacin - prevents spread
Antibiotic therapy can lead to emergence of resistant strains

Question 19

Considerations when treating gastroenteritis with antibiotics

Answer 19

Commonly caused by viruses - antibiotic therapy not effective
Resolve without antibiotic within a week
Treat with antibiotic can kill competing symbiotic bacteria increasing disease severity
Only in severe cases