Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

MD3002 - GI Disease/Pathology > Bacterial and Viral Infections of the GI Tract > Flashcards

Bacterial and Viral Infections of the GI Tract Flashcards

1
Q

How can gastrointestinal pathogens cause damage to the GI tract?

A
  • Local inflammation
  • Ulceration/perforation of mucosal epithelium
  • Disruption of normal microbiota
  • Pharmacological action of bacterial toxins
  • Invasion to blood or lymphatics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is e.cadherin important for?

A

the intergrity of tight junctions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the potential consequences of epithelial perforation?

A
  • ruptured/perforated ulcer
  • lining of mucosa is perforated
  • leaking of food and gastric juices to the peritoneal or abdominal cavities (spreading infection)
  • treatment requires surgery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q
A

top = normal SI villi

bottom = villous atrophy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What bacteria are likely to cause bloody stools?

A

Campylobacter and Shigella

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What bacteria are likely to cause watery stools?

A

EPEC and cholera

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the main bacterial diarrhoeal pathogens?

A

Gram negative

  • Vibrio cholerae
  • Escherichia coli
  • Campylobacter jejuni
  • Salmonella spp.
  • Shigella spp.

Gram positive

  • Listeria monocytogenes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe Vibrio cholerae

A
  • Gram negative
  • Comma-shaped rod
  • Flagellated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is Vibrio cholerae characterised by?

A

epidemics and pandemics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where does Vibrio cholerae flourish?

A

communities with no clean drinking water/sewage disposal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What type of pathogen is Vibrio cholerae

A

human-only pathogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What type of antigens is Vibrio cholerae based on?

A
  • O1 - early pandemics
  • Non-O1 - recent outbreaks
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What vaccines are avaliable for Vibrio cholerae?

A
  • parenternal vaccine: low protective efficiency
  • Oral vaccine: effective and suitable for travels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the pathogenesis of Vibrio cholerae

A
  • Only infective in large doses
  • Many organisms killed in stomach
  • Colonisation of small intestine involving flagellar motion, mucinase, attachment to specific receptors
  • Production of multicomponent toxin
  • Loss fluid and electrolytes without damage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the building blocks of the cholera toxin (CTx) and what is it responsible for?

A
  • Oligomeric complex of 6 protein subunits:
    • 1 copy of A subunit (enzymatic)
    • 5 copies of B subunit (receptor binding)
  • Responsible for the characteristic, watery cholera diarrhoea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the consequences of the cholera infection?

A
  • Fluid loss of up to 1 litre/hour
  • Electrolyte imbalance leading to dehydration, metabolic acidosis and hypokalaemia
  • Hypovolaemic shock
  • 40-60% mortality
  • <1% mortality if given fluid/electrolytes (ORT)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Dsecribe the bacteria Escherichia coli

A
  • Gram negative
  • Bacillus
  • Member of normal gastrointestinal microbiota
  • Some strains possess virulence factors enabling them to cause disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the 6 main types of E.coli causing GI infections?

A
  • EPEC - Enteropathogenic
  • ETEC - Enterotoxigenic
  • VTEC/STEC - Verocytotocin-producing
  • EHEC - Enterohaemorrhagic
  • EIEC - Enteroinvasive
  • EAEC - enteroaggregative
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When is EPEC common?

A

sporadic cases and outbreaks of infection in under 5s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

When is ETEC common?

A

“travellers’ diarrhoea” (occurs in 20-50% of travellers)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

When is VTEC/EHEC common?

A

sporadic cases and outbreaks of gastroenteritis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

When is EIEC common?

A

food-borne infection in areas of poor hygiene (often persistent diarrhoea)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where is EAEC common?

A

resource-poor cpountries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the mode of action of E.coli enterotoxins?

A

LT =. Heat-labile toxin

Sta = heat-stable toxin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Describe Campylobacter jejuni bacteria
* Gram negative * Helical bacillus
26
What is the resovoir for C. jejuni
large animal resovoir
27
What type of diarrhoea does C.jejuni
food-associated diarrhoea Commonest case of diarrhoea in developed world
28
What is the mode of transmission of C.jejuni?
Transmission through consumption of raw/undercooked meat, contaminated milk
29
Describe the pathogenesis and histological appearance of C. jejuni
* Mucosal inflammation and fluid secretion * Inflammation involves entire mucosa * Villous atrophy * Necrotic debris in crypts * Thickening of basement membrane
30
Describe Salmonella spp.
* gram negative * bacilli * \> 200 serotypes of salmonella spp.
31
What type of diarrhoea does salmonella spp. cause?
food-associated diarrhoea
32
What is the mode of transmission of Salmonella spp.
* Transmission through consumption of raw/undercooked meat, contaminated eggs and milk * Secondary spread can be human-human
33
What are the most important species of salmonella spp.
* S. typhi * S. paratyphi * S. enteritidis
34
What is the pathogenesis of salmonella spp.
* Ingestion of large numbers of bacteria * Absorption to epithelial cells in terminal section of small intestine * Penetration of cells and migration to lamina propria * Multiplication in lymphoid follicles inflammatory response mediates release of prostaglandins * Stimulation of cyclic AMP * Release of fluid and electrolytes causing diarrhoea
35
What can s.thyphi and s.paratyphi cause?
* Cause enteric fevers: typhoid and paratyphoid * Systemic infections initiated in gastrointestinal tract
36
Describe the consequences for a patient who gets thyphoid fever
* Patient can excrete S. typhi in faeces for several weeks after recovery * 1-3% become chronic carriers, most common in women and the elderly * Public health concern * It’s a notifiable disease
37
What are the vaccinations avaliable for thyoid?
* Oral; live attenuated * Booster after 5 years * Parenteral; capsular polysaccharide * Booster after 2 years * 50-80% effective * Recommended for travellers to endemic areas
38
Describe the shigella spp. bacteria
* Bacillus * Cause shigellosis (bacillary dysentery) * Human-only pathogen
39
What are the 4 species of Shigella spp.?
* S. dysenteriae: most serious * S. flexneri: severe disease * S. boydii: severe disease * S. sonnei: mild infections
40
Describe the pathogenesis of shigella infection
* Attaches to mucosal epithelium of distal ileum and colon * Causes inflammation and ulceration * Rarely invasive * Produces Shiga toxin (STx) * Diarrhoea watery initially, later can contain blood and mucus * Disease usually self-limiting
41
Describe Listeria monocytogenes
* Coccobacillus * Causes listeriosis * Food-borne pathogen associated with pâté, soft cheese, unpasteurised milk * \< 1000 organisms may cause disease
42
What population are at risk of listeria?
* Pregnant women (with possibility of infection of the baby in utero or at birth) * Immunosuppressed individuals (e.g. those with AIDS or on cancer/immunosuppressive drugs) * The elderly
43
What does listeria usually present as?
meningitis
44
What are the 3 main viral diarrhoeal pathogens?
* Rota virus * Norovirus * Enteric Adenovirus
45
Describe the rotavirus
* “rota” – wheel * 11 separate segments of double-stranded RNA * Infects many mammals * Infection commonest in children \<2 years old * As few as 10 ingested particles can causes disease * Seasonal occurrence (commonest in cooler months)
46
What is the transmission mode of rotavirus?
Transmission is faeco-oral, but may also be faecal-respiratory
47
Describe the pathogenesis of rotavirus
* Incubation period of 1-2 days * Replication of virus in small intestinal epithelial cells at tips of villi * Results in callous atrophy * Damage caused to infected cells leaving immature cells with reduced absorptive capacity for sugar, water and electrolytes * Onset of vomiting, diarrhoea lasting 4-7 days * Up to 1010-1011 virus particles/gram faeces released
48
What is the vaccination for rotavirus?
* RotaRix; RotaTeq * Oral administration (2-3 doses) * First dose at 6-10 weeks of age * Live, attenuated virus
49
What is norovirus known as?
A.k.a “winter vomiting disease” Accounts for most non-bacterial outbreaks worldwide
50
What type of pathogen is norovirus?
human-only pathogen
51
What is the mode of transmission of norovirus?
* Transmission is faeco-oral, contaminated water/shellfish, fomites * \<100 virions can establish infection
52
What is the vaccine for the norovirus?
* None yet * Still approx. 4-5 years away * No vaccine is ever 100% effective * Hand washing
53
Describe enteric adenovirus
* Accounts for 10% of community-acquired diarrhoeas in young children * No seasonal incidence * Asymptomatic infections common * Mild, but prolonged diarrhoea
54
What are the other diarrhoeal viruses outside the 3 most common ones?
Calicivirus Coronavirus Astrovirus
55
Desccribe anti-biotic associated diarrhoea
* Does NOT involve ingestion of pathogen or toxin * Can arise from disruption of gut microbiota following antibiotic therapy
56
Give the consequences of some antibiotics on the gut microbiota
* Tetracycline – allows colonisation by Staphylococcus aureus and Candida spp. * Clindamycin suppresses gut microbiota and allows Clostridium difficile to multiply * C. difficile infection is now associated with resistance to vancomycin
57
Describe the C.difficile infection
* Produces spores for survival * Produces an enterotoxin and a cytotoxin
58
Describe Helicobacter pylori
* Gram negative * Spiral * Flagellated * Microaerophilic * \>80% infected individuals are asymptomatic
59
What diseases is H.pylori associated with?
* Duodenal ulcers * Gastric ulcers * Gastro-oesophageal reflux disease * Non-ulcer dyspepsia
60
What are the key features of H.pylori?
* Acid-inhibiting protein – survival in stomach * Urease – neutralisation of acid pH * Adhesins – binding to gastric epithelium * Cytotoxin – damage to gastric epithelium * Flagellum – movement through gastric mucus layer
61
What is the first-line treatment of H.pylori?
1 week (7 days) triple therapy Either: * Proton pump inhibitor (PPI), Clarithromycin and Amoxicillin OR * Proton pump inhibitor (PPI), Clarithromycin and Metronidazole
62
What is food poisoning?
Syndrome is restricted to diseases caused by toxins elaborated by contaminating bacteria in food before it is consumed
63
Give 3 examples of food poisoning toxins
* Emetic toxins of Bacillus cereus * Enterotoxin of staphylococcus aureus * Neurotoxin Clostridium botulinum
64
Describe food-associated GI infection of Clostridium perfrigens
* Usually caused by type A strains from animal guts and soil * Contamination of raw meat products * Spores survives cooking and germination takes place * Multiplication in large intestine, production of spores and enterotoxin * Damage to intestinal epithelium * Diarrhoea
65
What is Oral Rehydration therapy?
* Involves the replacement of fluids and electrolytes lost during diarrheal illness * 90-95% of cases of acute, watery diarrhoea can be successfully treated with an oral rehydration solution (ORS) * ORS increases the resorption of fluids and salts into the intestinal wall
66
What are the ingredients of ORT?
* Glucose (anhydrous): 13.6g/L * Sodium chloride: 2.6g/L * Potassium chloride: 1.5g/L * Trisodium citrate dihydrate: 2.9g/L * In addition, fruit juices, coconut water, and other indigenous solutions can adequately approximate ORS

MD3002 - GI Disease/Pathology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions