GI Infections Flashcards
Key organs of the gastrointestinal (GI) tract
Mouth
Stomach
Small intestine
Large intestine
Main functions of the GI tract
Absorb nutrients + excretion of waste products
Requires
- breakdown of large molecules
- secretion of enzymes
- transport mechanisms
- secretion of compounds to aid absorption
Resident microflora of GI tract
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
Role of GI microbiota
Digest material human enzymes can’t do + handle nutrients
Compete with pathogenic microorganisms
Influences immune system
GI tract infections are caused by…
Viruses, bacteria, protozoa +worms
Common cause of GI tract infection
Viruses
Key routes of entry of pathogens into GI tract
Ingestion of contaminated food or water
Poor hygiene
Cause of Peridontal disease
Caused by build up of plaque - a biofilm produced by bacteria
Symptoms of Gastroenteritis
Vomiting +/or diarrhoea, pain + cramps
- self-limiting
- does not need treatment (unless severe therefore use of antibiotic needed)
Gastroenteritis
Inflammation of GI mucosa - include stomach + duodenum
How can you contract Gastroenteritis
Eating contaminated food/water
Person-person contact
Common cause of Gastroenteritis + diarrhoeal disease
Campylobacter sp.
Campylobacter sp.
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
Salmonella sp.
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
Characterise Salmonellosis
Non-bloody diarrhoea, nausea + vomiting
Salmonella typhi causes
Typhoid fever
Which Salmonella serotype causes gastroenteritis
S.enterica
Shigella
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
Considerations when treating gastroenteritis with antibiotics
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
