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Infection > Diarrhoea > Flashcards

Diarrhoea Flashcards

1
Q

What is diarrhoea?

A

Subjective - increase in fluidity or frequency of stools

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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
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3
Q

What is dysentery?

A

Large bowel inflammation, resulting in severe diarrhoea with blood/mucus in stools

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4
Q

What are the main bacteria responsible for causing diarrhoea in the UK?

A

Salmonella
Clostridium difficile
Campylobacter
E. coli O157

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5
Q

What campylobacter species are most commonly responsible for causing diarrhoea in the UK?

A

C. jejuni

C. coli

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6
Q

What is the commonest cause of bacterial food poisoning in the UK?

A

Campylobacter

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7
Q

What are the sources of campylobacter causing food poisoning?

A

Chickens
Contaminated milk
Puppies

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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

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9
Q

Symptoms/signs of campylobacter infection

A

Severe abdominal pain

Colitic picture e.g. pain, diarrhoea

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10
Q

How long does it usually take a campylobacter infection to clear?

A

3 weeks

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11
Q

How are Salmonella species screened for?

A

Screened out as lactose non-fermenters, followed by antigen and further biochemical tests

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12
Q

Most serotypes of salmonella causing diarrhoea are of the same species - what is this?

A

Salmonella enterica

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13
Q

What are the commonest isolates of salmonella species causing diarrhoea in the UK?

A

Salmonella enteritidis

Salmonella typhimurium

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14
Q

What salmonella species cause enteric fever rather than gastroenteritis?

A

S. typhi and S. paratyphi

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15
Q

Features of salmonella gastritis

A

Symptom onset usually < 48 hours after exposure

Diarrhoea usually lasts < 10 days

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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

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17
Q

What might prolonged carriage of salmonella be associated with?

A

Gallstones

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18
Q

What is a common post-infective side effect of salmonella gastroenteritis?

A

Post-infectious irritable bowel

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19
Q

What kind of bacteria is E. coli O157?

A

Enterohaemorrhagic gram negative bacilli

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20
Q

What is the source of E. coli O157?

A

Cattle reservoir

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21
Q

When does excretion of E. coli O157 typically occur?

A

3 weeks after symptoms

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22
Q

What is the time frame between onset of diarrhoea and HUS in E. coli O157 infection?

A

5-9 days

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23
Q

Shigella infection is largely a disease of

A

childhood and travel

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24
Q

What kind of bacteria is shigella?

A

Gram negative anaerobic

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25
Q

What is leading to the resistance of Shigella?

A

Widespread quinolone use against shigellosis in the developing world

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26
Q

What would be typical of a history of a patient with clostridium difficile diarrhoea?

A

History of previous antibiotic therapy - particularly the four C antibiotics (clindamycin, cephalosporins, co-amoxiclav, ciprofloxacin)

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27
Q

How do antibiotics increase the risk of C. diff diarrhoea?

A

Knock out the normal gut flora, reducing competition for C. diff

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28
Q

Range of severity of C. diff diarrhoea

A

Ranges from mild diarrhoea to severe colitis, which can result in death particularly in the elderly or those with co-morbidities

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29
Q

What toxins are produced by C. diff?

A

Enterotoxin A
Cytotoxin B

These cause damage to the colonocytes

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30
Q

What is the treatment of C. diff diarrhoea?

A

Further antibiotic therapy

Metronidazole 
Oral vancomycin 
Fidaxomicin (new and expensive) 
Stool transplants
Surgery
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31
Q

Why is oral vancomycin a suitable treatment for C. diff diarrhoea?

A

It is not absorbed anywhere else in the GI tract so produces a local effect on colon

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32
Q

What might C. diff diarrhoea result in?

A

Pseudomembranous colitis

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33
Q

What account for 80% of tourist infections (traveller’s diarrhoea)?

A

Enterotoxigenic E. coli
Campylobacter
Shigella

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34
Q

What fraction of travellers from industrialised to developing countries will develop a bout of diarrhoea?

A

about 1/3

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35
Q

How long does traveller’s diarrhoea normally last?

A 
Usually lasts < 1 week 
Persistent diarrhoea (> 30 days) occurs in 1-3% 
Significantly shortened by antibiotics
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36
Q

What other bacteria less commonly cause diarrhoea?

A

Shigella (shigella sonnei in nurseries)

Several other forms of E. coli

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37
Q

What other organisms are occasionally responsible for causing food poisoning outbreaks?

A

Staphylococcus Aureus
Bacillus Cereus
Clostridium Perfringens

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38
Q

How is routine bacterial culture of stools carried out?

A

Routinely look for four pathogens
Selective and enrichment method
Takes 3 days to complete all tests
Difficult to find pathogen in the complex flora

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39
Q

What are the parasites commonly detected in stool specimens in the UK?

A

Protozoa
Helminths
Giardia Lamblia
Cryptosporidium Parvum

Diagnosis by microscopy

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40
Q

What percentage of diarrhoea in developed countries are cryptosporidiosis species responsible for?

A

3-6%

41
Q

How is cryptosporidiosis transmitted?

A

Water-borne outbreaks

Cattle are the principal reservoir

42
Q

Features of cryptosporidiosis infection in the immunocompromised

A

Self limiting but protracted illness

43
Q

Transmission and treatment of Giardia infection

A

Present in surface water
Asymptomatic carriers
Treatment with metronidazole/tinidazole

44
Q

What disease might entamoeba histolytica mimic?

A

Ulcerative colitis

45
Q

How is symptomatic entamoeba histolytica infection treated?

A

10/7 metronidazole

Furamide for cyst carriage

46
Q

Features of Giardia Lamblia infection

A

Spread in infected water
Diarrhoea, malabsorption and failure to thrive
Vegetative form in duodenal biopsy or string test
Cysts seen on stool microscopy

47
Q

Treatment of Giardia Lamblia infection

A

Metronidazole

48
Q

In what patients was cryptosporidium first recognised?

A

Patients with AIDS

49
Q

Features of Cryptosporidium Parvum infection

A

Spread in contaminated water (from animal faeces)
Cysts seen on microscopy
No treatment

50
Q

Features of infection due to imported parasites

A

Vegetative form in symptomatic patient
Cysts seen in asymptomatic patient
Amoebic liver abscess as long-term complication
Treatment with metronidazole

51
Q

At what time of year is viral diarrhoea most common?

A

Winter

52
Q

How is viral diarrhoea diagnosed?

A

Antigen detection

53
Q

Common causes of viral diarrhoea

A

Rotavirus
Adenovirus
Norovirus

54
Q

In what settings is viral diarrhoea due to norovirus most common?

A

Hospitals
Community
Cruise ships
etc.

55
Q

How is norovirus infection diagnosed?

A

Viral DNA PCR

56
Q

Treatment of norovirus infection

A

Supportive
Ward closures
Strict infection control measures

57
Q

What is food poisoning?

A

Illness caused by bacteria or other toxins in food, typically with vomiting and diarrhoea

58
Q

What is gastroenteritis?

A

Inflammation of the stomach and intestines, typically resulting from bacterial toxins or viral infection and causing vomiting and diarrhoea

59
Q

What is dysentery?

A

Infection of the intestines resulting in severe diarrhoea with the presence of blood and mucus in the faeces

60
Q

What is colitis?

A

Inflammation of the colon

61
Q

What factors affect the host’s natural defence against enteric infection?

A 
Age 
Hygiene 
Gastric acid 
Gut motility 
Normal flora 
Gut immunity
62
Q

Possible sources of infection causing gastroenteritis

A

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
Q

What percentage of the population will have an infectious intestinal disorder each year?

A

25%

64
Q

What percentage of the population will visit their GP due to a GI infection each year?

A

2%

65
Q

What is the commonest cause of gastroenteritis?

A

Viral infection

Campylobacter is the most common bacterial pathogen

66
Q

What is the most common viral cause of gastroenteritis?

A

Rotavirus

67
Q

How many deaths are caused yearly by rotavirus in children under 5?

A

> 800,000

68
Q

What is the route of transmission of rotavirus?

A

Faecal-oral

69
Q

How does rotavirus result in gastroenteritis?

A

Infects mature enterocytes of the villous body and tip resulting in cell death and lactose intolerance

70
Q

How many cases of food poisoning from known pathogens are there per year?

A

more than 500,000

71
Q

What is the most common food-borne cause of food poisoning?

A

Campylobacter

72
Q

How can C. diff infection be prevented?

A

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
Q

Management of C. diff infection

A

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
Q

Mechanisms by which infecting organisms can cause diarrhoea

A

Toxin mediated
Invasion
Attachment

75
Q

Features of non-inflammatory diarrhoea

A 
Secretory toxin mediated e.g. cholera or enterotoxigenic E. coli 
Frequent watery stools 
Little abdominal pain 
Rapid dehydration 
Treated with rehydration therapy
76
Q

Features of inflammatory diarrhoea

A

Inflammatory toxin damage and mucosal destruction
Pain and fever
Bacterial infection or amoebic dysentery
Rehydration therapy often sufficient, antimicrobials may be appropriate

77
Q

What percentage of patients given antimicrobials will get diarrhoea?

A

5-10%

78
Q

In what percentage of antibiotic-associated diarrhoea is C. diff the causative organism?

A

10-15%

79
Q

What percentage of patients carry C. diff when;
coming into hospital
leaving hospital?

A

Coming into hospital - 7%

Leaving - 28%

80
Q

What percentage of stool cultures and toxin detection in C. diff infection will have false negatives?

A

up to 33%

81
Q

Defences against enteric infections

A

Hygiene
Stomach acidity
Normal flora
Immunity

82
Q

Important features when assessing a patient with diarrhoea

A

Symptoms and their duration
Risk of food poisoning
Assess hydration
Features of inflammation

83
Q

Over what length of time is diarrhoea unlikely to be due to infective gastroenteritis?

A

> 2 weeks

84
Q

Important aspects of history when determining risk of food poisoning

A 
Dietary 
Contact 
Travel history 
Occpation 
Institution
85
Q

Ways to assess hydration

A 
Postural BP 
Skin turgor 
Urine flow 
Patient appearance 
Muscle cramps
86
Q

Features of inflammation

A

Fever
Raised WCC
Tachycardia
Raised respiratory rate

87
Q

How to assess children for dehydration

A

Skin turgor
Sunken eyes, cheeks, fontanelle
Few or no tears produced
Dry mouth/tongue

88
Q

How does diarrhoea affect fluids and electrolytes?

A

Fluid and electrolyte loss, can be severe in secretory diarrhoea
Hyponatraemia due to sodium loss with fluid replacement

89
Q

Investigations commonly done for patients with diarrhoea

A 
Stool culture 
Blood culture 
Renal function 
Blood count 
Sigmoidoscopy 
Abdominal x-ray
90
Q

Differential diagnoses for diarrhoea

A 
Inflammatory bowel disease 
Spurious diarrhoea 
Carcinoma 
Obstructive pathology 
Sepsis
91
Q

Common treatments of diarrhoea

A

Rehydration
Fasting
Antimicrobials
Treatment of complications

92
Q

Features of campylobacter gastroenteritis

A 
Up to 7 day incubation 
Stools negative within 6 weeks 
Abdominal pain very severe 
< 1% invasive 
Post-infective sequelae
93
Q

When are antibiotics indicated in the treatment of gastroenteritis?

A 
Immunocompromised patients 
Severe sepsis or invasive infection 
Valvular heart disease 
Chronic illness 
Diabetes
94
Q

Typical characteristics of E. coli O157 infection

A

Frequent bloody stools
Not dehydrated as severely as in other forms of diarrhoea
Abdominal pain

95
Q

What is haemolytic-uraemic syndrome (HUS) and how is it caused by E. coli O157?

A

Haemolytic anaemia, renal failure and thrombocytopenia

E. coli O157 produces verocytotoxin which gets into the blood and causes HUS

96
Q

Characteristics of HUS

A 
Haemolytic anaemia which may result in breathlessness and fatigue 
Renal failure 
Thrombocytopenia 
Low platelet count 
Lactate dehydrogenase
97
Q

What is the treatment of HUS? In what groups of patients are complications more common?

A

Treatment is supportive, antibiotics not indicated

Commoner in the very young, elderly, or those with co-morbidities

98
Q

Within what time frame will HUS occur following E. coli O157 infection?

A

Within 10 days of diarrhoea onset

99
Q

Pathophysiology of haemolytic-uraemia syndrome

A 
Toxin binds to globotriaosylceramide
Platelet activation stimulated 
Micro-angiopathy 
Attachment to endothelial, glomerular, tubule and mesangial cells 
Progressive uraemia/renal failure

Infection (14 decks)

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