Diarrhoea Flashcards
(99 cards)
1
Q
What is diarrhoea?
A
Subjective - increase in fluidity or frequency of stools
2
Q
How is gastroenteritis defined?
A
3 or more loose stools in 24 hours plus one of; fever vomiting pain blood/mucus in stools
3
Q
What is dysentery?
A
Large bowel inflammation, resulting in severe diarrhoea with blood/mucus in stools
4
Q
What are the main bacteria responsible for causing diarrhoea in the UK?
A
Salmonella
Clostridium difficile
Campylobacter
E. coli O157
5
Q
What campylobacter species are most commonly responsible for causing diarrhoea in the UK?
A
C. jejuni
C. coli
6
Q
What is the commonest cause of bacterial food poisoning in the UK?
A
Campylobacter
7
Q
What are the sources of campylobacter causing food poisoning?
A
Chickens
Contaminated milk
Puppies
8
Q
What pattern of infection does campylobacter result in?
A
Isolated cases rather than outbreaks - person-to-person spread is rare, outbreaks would have to result from a common contaminated source
9
Q
Symptoms/signs of campylobacter infection
A
Severe abdominal pain
Colitic picture e.g. pain, diarrhoea
10
Q
How long does it usually take a campylobacter infection to clear?
A
3 weeks
11
Q
How are Salmonella species screened for?
A
Screened out as lactose non-fermenters, followed by antigen and further biochemical tests
12
Q
Most serotypes of salmonella causing diarrhoea are of the same species - what is this?
A
Salmonella enterica
13
Q
What are the commonest isolates of salmonella species causing diarrhoea in the UK?
A
Salmonella enteritidis
Salmonella typhimurium
14
Q
What salmonella species cause enteric fever rather than gastroenteritis?
A
S. typhi and S. paratyphi
15
Q
Features of salmonella gastritis
A
Symptom onset usually < 48 hours after exposure
Diarrhoea usually lasts < 10 days
16
Q
Features of blood and stool cultures in patients with salmonella gastroenteritis
A
< 5% will have positive blood cultures
20% of patients will still have positive stool cultures at 20 weeks
17
Q
What might prolonged carriage of salmonella be associated with?
A
Gallstones
18
Q
What is a common post-infective side effect of salmonella gastroenteritis?
A
Post-infectious irritable bowel
19
Q
What kind of bacteria is E. coli O157?
A
Enterohaemorrhagic gram negative bacilli
20
Q
What is the source of E. coli O157?
A
Cattle reservoir
21
Q
When does excretion of E. coli O157 typically occur?
A
3 weeks after symptoms
22
Q
What is the time frame between onset of diarrhoea and HUS in E. coli O157 infection?
A
5-9 days
23
Q
Shigella infection is largely a disease of
A
childhood and travel
24
Q
What kind of bacteria is shigella?
A
Gram negative anaerobic
25
What is leading to the resistance of Shigella?
Widespread quinolone use against shigellosis in the developing world
26
What would be typical of a history of a patient with clostridium difficile diarrhoea?
History of previous antibiotic therapy - particularly the four C antibiotics (clindamycin, cephalosporins, co-amoxiclav, ciprofloxacin)
27
How do antibiotics increase the risk of C. diff diarrhoea?
Knock out the normal gut flora, reducing competition for C. diff
28
Range of severity of C. diff diarrhoea
Ranges from mild diarrhoea to severe colitis, which can result in death particularly in the elderly or those with co-morbidities
29
What toxins are produced by C. diff?
Enterotoxin A
Cytotoxin B
These cause damage to the colonocytes
30
What is the treatment of C. diff diarrhoea?
Further antibiotic therapy
```
Metronidazole
Oral vancomycin
Fidaxomicin (new and expensive)
Stool transplants
Surgery
```
31
Why is oral vancomycin a suitable treatment for C. diff diarrhoea?
It is not absorbed anywhere else in the GI tract so produces a local effect on colon
32
What might C. diff diarrhoea result in?
Pseudomembranous colitis
33
What account for 80% of tourist infections (traveller's diarrhoea)?
Enterotoxigenic E. coli
Campylobacter
Shigella
34
What fraction of travellers from industrialised to developing countries will develop a bout of diarrhoea?
about 1/3
35
How long does traveller's diarrhoea normally last?
```
Usually lasts < 1 week
Persistent diarrhoea (> 30 days) occurs in 1-3%
Significantly shortened by antibiotics
```
36
What other bacteria less commonly cause diarrhoea?
Shigella (shigella sonnei in nurseries)
| Several other forms of E. coli
37
What other organisms are occasionally responsible for causing food poisoning outbreaks?
Staphylococcus Aureus
Bacillus Cereus
Clostridium Perfringens
38
How is routine bacterial culture of stools carried out?
Routinely look for four pathogens
Selective and enrichment method
Takes 3 days to complete all tests
Difficult to find pathogen in the complex flora
39
What are the parasites commonly detected in stool specimens in the UK?
Protozoa
Helminths
Giardia Lamblia
Cryptosporidium Parvum
Diagnosis by microscopy
40
What percentage of diarrhoea in developed countries are cryptosporidiosis species responsible for?
3-6%
41
How is cryptosporidiosis transmitted?
Water-borne outbreaks
| Cattle are the principal reservoir
42
Features of cryptosporidiosis infection in the immunocompromised
Self limiting but protracted illness
43
Transmission and treatment of Giardia infection
Present in surface water
Asymptomatic carriers
Treatment with metronidazole/tinidazole
44
What disease might entamoeba histolytica mimic?
Ulcerative colitis
45
How is symptomatic entamoeba histolytica infection treated?
10/7 metronidazole
| Furamide for cyst carriage
46
Features of Giardia Lamblia infection
Spread in infected water
Diarrhoea, malabsorption and failure to thrive
Vegetative form in duodenal biopsy or string test
Cysts seen on stool microscopy
47
Treatment of Giardia Lamblia infection
Metronidazole
48
In what patients was cryptosporidium first recognised?
Patients with AIDS
49
Features of Cryptosporidium Parvum infection
Spread in contaminated water (from animal faeces)
Cysts seen on microscopy
No treatment
50
Features of infection due to imported parasites
Vegetative form in symptomatic patient
Cysts seen in asymptomatic patient
Amoebic liver abscess as long-term complication
Treatment with metronidazole
51
At what time of year is viral diarrhoea most common?
Winter
52
How is viral diarrhoea diagnosed?
Antigen detection
53
Common causes of viral diarrhoea
Rotavirus
Adenovirus
Norovirus
54
In what settings is viral diarrhoea due to norovirus most common?
Hospitals
Community
Cruise ships
etc.
55
How is norovirus infection diagnosed?
Viral DNA PCR
56
Treatment of norovirus infection
Supportive
Ward closures
Strict infection control measures
57
What is food poisoning?
Illness caused by bacteria or other toxins in food, typically with vomiting and diarrhoea
58
What is gastroenteritis?
Inflammation of the stomach and intestines, typically resulting from bacterial toxins or viral infection and causing vomiting and diarrhoea
59
What is dysentery?
Infection of the intestines resulting in severe diarrhoea with the presence of blood and mucus in the faeces
60
What is colitis?
Inflammation of the colon
61
What factors affect the host's natural defence against enteric infection?
```
Age
Hygiene
Gastric acid
Gut motility
Normal flora
Gut immunity
```
62
Possible sources of infection causing gastroenteritis
Contamination of foodstuffs - intensity of farming
Storage of produce e.g. bacterial proliferation to infective doses at room temperature
Travel related infections e.g. Salmonella
Person-to-person spread e.g. norovirus
63
What percentage of the population will have an infectious intestinal disorder each year?
25%
64
What percentage of the population will visit their GP due to a GI infection each year?
2%
65
What is the commonest cause of gastroenteritis?
Viral infection
| Campylobacter is the most common bacterial pathogen
66
What is the most common viral cause of gastroenteritis?
Rotavirus
67
How many deaths are caused yearly by rotavirus in children under 5?
> 800,000
68
What is the route of transmission of rotavirus?
Faecal-oral
69
How does rotavirus result in gastroenteritis?
Infects mature enterocytes of the villous body and tip resulting in cell death and lactose intolerance
70
How many cases of food poisoning from known pathogens are there per year?
more than 500,000
71
What is the most common food-borne cause of food poisoning?
Campylobacter
72
How can C. diff infection be prevented?
Reduction in broad spectrum antibiotic prescribing
Avoid the 4C antibiotics
Antimicrobial management team and local antibiotic policy
Isolate symptomatic patients
Ensure hand washing between patients
73
Management of C. diff infection
Stop the precipitating antibiotic if possible
Oral metronidazole if no severity markers are present
Oral vancomycin if 2 or more severity markers are present
74
Mechanisms by which infecting organisms can cause diarrhoea
Toxin mediated
Invasion
Attachment
75
Features of non-inflammatory diarrhoea
```
Secretory toxin mediated e.g. cholera or enterotoxigenic E. coli
Frequent watery stools
Little abdominal pain
Rapid dehydration
Treated with rehydration therapy
```
76
Features of inflammatory diarrhoea
Inflammatory toxin damage and mucosal destruction
Pain and fever
Bacterial infection or amoebic dysentery
Rehydration therapy often sufficient, antimicrobials may be appropriate
77
What percentage of patients given antimicrobials will get diarrhoea?
5-10%
78
In what percentage of antibiotic-associated diarrhoea is C. diff the causative organism?
10-15%
79
What percentage of patients carry C. diff when;
coming into hospital
leaving hospital?
Coming into hospital - 7%
| Leaving - 28%
80
What percentage of stool cultures and toxin detection in C. diff infection will have false negatives?
up to 33%
81
Defences against enteric infections
Hygiene
Stomach acidity
Normal flora
Immunity
82
Important features when assessing a patient with diarrhoea
Symptoms and their duration
Risk of food poisoning
Assess hydration
Features of inflammation
83
Over what length of time is diarrhoea unlikely to be due to infective gastroenteritis?
> 2 weeks
84
Important aspects of history when determining risk of food poisoning
```
Dietary
Contact
Travel history
Occpation
Institution
```
85
Ways to assess hydration
```
Postural BP
Skin turgor
Urine flow
Patient appearance
Muscle cramps
```
86
Features of inflammation
Fever
Raised WCC
Tachycardia
Raised respiratory rate
87
How to assess children for dehydration
Skin turgor
Sunken eyes, cheeks, fontanelle
Few or no tears produced
Dry mouth/tongue
88
How does diarrhoea affect fluids and electrolytes?
Fluid and electrolyte loss, can be severe in secretory diarrhoea
Hyponatraemia due to sodium loss with fluid replacement
89
Investigations commonly done for patients with diarrhoea
```
Stool culture
Blood culture
Renal function
Blood count
Sigmoidoscopy
Abdominal x-ray
```
90
Differential diagnoses for diarrhoea
```
Inflammatory bowel disease
Spurious diarrhoea
Carcinoma
Obstructive pathology
Sepsis
```
91
Common treatments of diarrhoea
Rehydration
Fasting
Antimicrobials
Treatment of complications
92
Features of campylobacter gastroenteritis
```
Up to 7 day incubation
Stools negative within 6 weeks
Abdominal pain very severe
< 1% invasive
Post-infective sequelae
```
93
When are antibiotics indicated in the treatment of gastroenteritis?
```
Immunocompromised patients
Severe sepsis or invasive infection
Valvular heart disease
Chronic illness
Diabetes
```
94
Typical characteristics of E. coli O157 infection
Frequent bloody stools
Not dehydrated as severely as in other forms of diarrhoea
Abdominal pain
95
What is haemolytic-uraemic syndrome (HUS) and how is it caused by E. coli O157?
Haemolytic anaemia, renal failure and thrombocytopenia
E. coli O157 produces verocytotoxin which gets into the blood and causes HUS
96
Characteristics of HUS
```
Haemolytic anaemia which may result in breathlessness and fatigue
Renal failure
Thrombocytopenia
Low platelet count
Lactate dehydrogenase
```
97
What is the treatment of HUS? In what groups of patients are complications more common?
Treatment is supportive, antibiotics not indicated
Commoner in the very young, elderly, or those with co-morbidities
98
Within what time frame will HUS occur following E. coli O157 infection?
Within 10 days of diarrhoea onset
99
Pathophysiology of haemolytic-uraemia syndrome
```
Toxin binds to globotriaosylceramide
Platelet activation stimulated
Micro-angiopathy
Attachment to endothelial, glomerular, tubule and mesangial cells
Progressive uraemia/renal failure
```
