M7: Bacteria affecting the GI Tract Flashcards
The Duodenum, Jejunum and Ileum all belong to what part of the GI tract?
Small intestine
The following belong to what part of the GI tract?
Transverse colon Ascending colon Descending colon Sigmoid colon Caecum Rectum
Large intestine
What is the function of normal gut flora? (5)
- Strengthen the gut integrity
- Shape the intestinal epithelium
- Harvest energy
- Protect against pathogens
- Regulate host immunity
What is a dysbiotic gut microbiota?
One which fails to provide the host with all the usual beneficial properties
Name a bacterium that can survive in the stomach
H. pylori
What bacteria can be found in the jejunum? (2)
- Enterococci
- Lactobacilli
What bacteria can be found in the ileum? (2)
- Enterobacteriaceae
- Bacteroides fragilis
What are the socio economic factors for diarrhoeal diseases? (3)
- Clear water
- Sewage disposal
- Food quality
What are the 2 main mechanisms for Diarrhoeal diseases?
- Invasive
- Exotoxin
What occurs during an invasive diarrhoeal disease?
Give an example of one
- Bacteria invades tissue of intestine resulting in necrosis
- Salmonella enteritis causes creamy abdomen, pus and blood in stool
What occurs during an exotoxin diarrhoeal disease?
Secretion into food
food poisoning
What are some features of Escherichia? (3)
- Gram negative rod
- Lactose positive
- Most common species is E. coli
Escherichia contain Fimbriae what are these?
- Fibres on cell surface thought to be important in
adhesion to host cells - Genes for these on chromosome
What diseases are caused by E. coli strains? (4)
- GI infections
- UTI
- Septic infections
- Neonatal meningitis
What is the Enteropathogenic E coli (EPEC) pathotype of E. coli? (3)
- Non-invasive
- Causes acute enteritis of infants
- Adheres to epithelium resulting in cytoskeletal rearrangement
What is the Enterotoxigenic E coli (ETEC) pathotype of E. coli? (3)
- Toxin mediated which causes adenylate cyclase ribosylation and cAMP accumulation leading to fluid secretion
- Signs like cramps, loose stools and acute enteritis
- Linked with travellers diarrhoea
What is the Entero-invasive E coli (EIEC) pathotype of E. coli? (3)
- Causes dysentery like-disease
- ## Invades epithelial cells of large intestine and multiplies there
What is the Vero cytotoxigenic E coli pathotype of E. coli? (3)
- Produces toxins (VT1 and VT2)
- Can lead to renal failure and blood diarrhoea
What is the basic virulence mechanism for EPEC? (3)
- Adherence to epithelium
- Cytoskeletal rearrangement
- Ca2+ and electrolyte
loss
What is the basic virulence mechanism for ETEC? (2)
- Toxin which causes adenylate cyclase ribosylation and cAMP accumulation.
- Leads to fluid secretion
What is the basic virulence mechanism for EIEC?
Epithelial cell invasion
What is the basic virulence mechanism for VTEC?
Verotoxin release
Give some features about Salmonella (3)
- Gram negative bacilli
- Inhabit animal intestine
- Non-lactose fermenter
Give some examples of salmonella species that cause humans harm (3)
- S.typhi
- S.paratyphi
- S.typhimurium
What is the pathogenesis of salmonella?
Bacteria attach to epithelium of ileal mucosa and invade and multiply in tissues
What are some symptoms of salmonella infection? (6)
- Cramps
- Diarrhoea
- Fever
- Vomiting
- Dehydration
- Renal failure
Give some features of Shigella (2)
- Gram negative rods
- Non-lactose fermenter
- Causes of bacillary dysentery (frequent passage of bloody mucopurulent stools)
Give some features of Klebsiella (3)
- Gram negative rod
- Lactose-fermenter
- Often pronounced capsule is present
What can cause Klebsiella infection? (3)
- UTI in children
- Wound infection
- Infection in surgery
Give some features of Proteus (3)
- Gram negative rod
- Lactose non-fermenter
- Motile (swarming on plates)
What can cause Proteus infection? (3)
- UTI in children
- Wound infection
- Infection in surgery
What does MacConkeys agar determine?
Whether a species is lactose fermenting
How does MacConkeys agar determine if a species in lactose fermenting?
- Lactose fermenting colonies are pink
- Non- lactose fermenters give yellow colonies
What does MacConkeys agar contain? (3)
- Bile salts
- Lactose as carbon source
- pH indicator
Give some features of Vibrio species (5)
- Gram negative rods
- Comma shaped
- Motile-polar flagellum
- Produce enterotoxins
- Causes cholera
What are some symptoms of Vibrio cholerae? (5)
- Vomiting
- Cramps
- Watery diarrhoea
- Rapid dehydration
- Death in 12-24 hours if untreated
Give some features about Campylobacter (3)
- Gram negative rods
- Slender spiral
- Most common cause of infective diarrhoea
Give some features of Helicobacter pylori (4)
- Gram negative rod
- Colonises stomach in gastric mucosa
- Causes gastritis
- Causes peptic ulcers
