Gi bacterial and viral infections Flashcards
(52 cards)
1
Q
what damage can GI pathogens do
A
local inflammation ulceration perforation of mucosal epithelium Disruption of normal microbiota Pharmacological action of bacterial toxins Invasion to blood or lymphatics villous atrophy
2
Q
describe types of epithelial perforation
A
Ruptured ulcer / perforated ulcer
may result in leaking of food and gastric juices to the abdominal cavities
3
Q
what pathogens can cause diarrhoea
A
campylobacter
shigella
EPEC
cholera
4
Q
how long can campylobacter incubate for
A
2-11 days
5
Q
how long can diarrhoea caused by campylobacter last for
A
3 weeks
6
Q
what symptoms may present with campylobacter or shigella
A
bloody stools
7
Q
what does EPEC stand for
A
enteropathogenic E. coli
8
Q
what may result from e.coli or cholera infection
A
watery stools
9
Q
what are some bacterial diarrhoeal pathogens
A
- Vibrio cholerae
- Escherichia coli
- Campylobacter jejuni
- Salmonella spp.
- Shigellaspp.
- Listeria monocytogenes
10
Q
describe V. cholerae
A
- Gram negative
- Comma-shaped rod
- Flagellated
found in water
11
Q
what is O1 antigen associated with
A
Associated with early pandemics
12
Q
what is non O1 antigen associated with
A
recent outbreaks
13
Q
what vaccines are available for cholera
A
- Parenteral vaccine: low protective efficiency
* Oral vaccine: effective & suitable for travellers
14
Q
describe the pathogenesis of V.cholerae
A
- Only infective in large doses
- Many organisms killed in stomach
- Colonisation of small intestine involving flagellarmotion, mucinase, attachment to specific receptors
- Production of multicomponent toxin
- Loss of fluid and electrolytes without damage to enterocytes
15
Q
what are the consequences of cholera infection
A
Fluid loss of up to 1 litre/hour •Electrolyte imbalance leading to dehydration, metabolic acidosis & hypokalemia •Hypovolaemicshock •40-60% mortality •
16
Q
describe E.coli
A
- Gram negative
- Bacillus
- Member of normal gastrointestinal microbiota
- Some strains possess virulence factors enabling them to cause disease
17
Q
what are the types of E. coli
A
- EPEC enteropathogenic
- ETEC enterotoxigenic
- VTEC verocytotoxin-producing
- EHEC enterohaemorrhagic
- EIEC enteroinvasive
- EAEC enteroaggregative
18
Q
what is EPEC (enteropathogenic) responsible for
A
sporadic cases and outbreaks of infection in under 5’s
19
Q
what is ETEC (enterotoxigenic) responsible for
A
travellers’ diarrhoea
20
Q
what is VTEC / EHEC (verocytoxin/ enterohaemorrhagic) responsible for
A
sporadic cases and outbreaks of gastroenteritis
21
Q
what is EIEC (enteroinvasive) responsible for
A
food-borne infection in areas of poor hygiene (often persistent diarrhoea)
22
Q
where is EAEC found (enteroaggregative e. coli)
A
resource-poor countries
23
Q
describe C. jejuni
A
- Gram negative
* Helical bacillus
24
Q
how is C. jejuni spread
A
consumption of raw / undercooked meat, contaminated milk
25
what does C. jejuni cause
Commonest case of diarrhoea in developed world
| Mucosal inflammation and fluid secretion
26
what is the histological appearance of C.jejuni infection
* Inflammation involves entire mucosa
* Villous atrophy
* Necrotic debris in crypts
* Thickening of basement membrane
27
what is Salmonella sp
Gram negative Bacilli
28
what does Salmonella do
food associated diarrhoea
| transmission through meat, eggs milk or human to human
29
describe the pathogenesis of Salmonella
* 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
30
what does S. typhi and S. paratyphi cause
typhoid and paratyphoid
travel around the body in macrophages
spread via faeces in contaminated water, can become a chronic carrier
31
describe typhoid vaccines
```
Oral; live attenuated
–booster after 5 years
•Parenteral; capsular polysaccharide
–Booster after 2 years
•50-80% effective
•Recommended for travellers to endemic areas
```
32
what is shigellosis
shigella infection causing dysentery
faecal- oral
human only
33
describe the pathogenesis of Shigella
* Attaches to mucosal epithelium of distal ileum and colon
* Causes inflammation and ulceration
* Rarely invasive
* Produces Shiga toxin
* Diarrhoea watery initially, later can contain blood and mucus
* Disease usually self-limiting
34
what is L. monocytogenes
* Coccobaccillus
* Causes listeriosis
* Food-borne pathogen associated with paté, soft cheese, unpasteurised milk
usually presents as meningitis
35
who is at risk of L.monocytogenes infection
–Pregnant women (with possibility of infection of the baby in uteroor at birth)
–Immunosuppressed individulas(e.g. those with AIDS or on cancer / immunosuppresivedrugs)
–The elderly
36
what viruses can cause diarrhoea
* Rotavirus
* Norovirus
* Enteric Adenovirus
more rarely:
•Calicivirus
•Coronavirus
•Astrovirus
37
describe rotavirus
```
looks like a wheel
infects mammals
commonest in very young children
high virulence
faeco-oral or faeco-respiratory
```
38
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 villous 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 1010–1011virus particles/gram faeces released
39
describe the rotavirus vaccine
```
•RotaRix; RotaTeq
–Oral administration (2-3 doses)
–First dose at 6-10 weeks of age
–Live, attenuated virus
•Introduced in UK from 2013
•In US, hospital admissions decreased by 86% since introduction
•Has already been used in >30 countries
```
40
what is norovirus
•a.k.a. “winter vomiting disease”
•Accounts for most non-bacterial outbreaks worldwide
•Past infection in 60% of adults
•Human only pathogen
•Transmission is faeco-oral, contaminated water / shellfish, fomites
•
41
what is enteric adenovirus
* Accounts for 10% of community-acquired diarrhoeas in young children
* No seasonal incidence
* Asymptomatic infections common
* Mild, but prolonged diarrhoea
42
what pathogen might multiply after tetracycline treatment
Staphylococcus aureus& Candida sp.
43
describe C. difficile
* Produces spores for survival
* Produces an enterotoxin and a cytotoxin
* Not only associated with antibiotic use
* Now associated with >55,000 cases in England/Wales per annum
* More severe disease associated strain 027 which produces more enterotoxin (toxin A) than cytotoxin(toxin B)
* Nosocomial infections largely responsible for increase in cases
44
describe the appearance of Helicobacter pylori
* Gram negative
* Spiral
* Flagellated
* Microaerophilic
* >80% infected individuals are asymptomatic
can cause stomach ulcers
45
what diseases can H. pylori cause
* Duodenal ulcers
* Gastric ulcers
* Gastro-oesophageal reflux disease
* Non-ulcer dyspepsia
46
what are the Key featurs 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
47
how is H. pylori treated
```
•1 week triple combination therapy
EITHER:
Proton pump inhibitor (PPI)
& Clarithromycin
& Amoxycillin
OR:
Proton pump inhibitor (PPI)
& Clarithromycin
& Metronidazole
```
48
what toxins can cause food poisoning
* emetic toxins of Bacillus cereus
* enterotoxin of Staphylococcus aureus
* neurotoxin of Clostridium botulinum
49
what is oral rehydration therapy
the replacement of fluids and electrolytes lost during diarrheal illness
contains glucose, NaCl, KCl, and other salts
50
what is listeriosis
after eating certain foods contaminated with listeria
causes mild fever, vomiting and diarrhoea
may cause meningitis
caused by L. monocytogenes
51
how long does shigella incubate for
1-4 days and lasts for 3 days
52
what might clindamycin lead to
c. difficile infection
