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3rd Year Infection > Infectious Diarrhoea > Flashcards

Infectious Diarrhoea Flashcards

1
Q

How is Gastro-enteritis defined?

A

3+ loose stools/day

Accompanying features

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2
Q

How is Dysentery defined?

A

Large bowel inflammation

Bloody stools

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3
Q

How is gastro-enteritis spread?

A

Contaminated foodstuffs
Poor food storage
Travel-related infections
Person-person spread

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4
Q

What gastro-enteritis bacteria is associated with contaminated foodstuffs?

A

Campylobacter

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5
Q

Which foodstuff is most commonly associated with food poisoning?

A

Poultry

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6
Q

What are the defences against enteric infections?

A

Hygiene
Stomach acidity
Normal gut flora
Immunity

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7
Q

What are the clinical features of diarrhoeal illness?

A

Inflammatory/non-inflammatory

Mixed

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8
Q

What are the clinical features of non-inflammatory diarrhoeal illness?

A
  • Secretory Toxin-mediated
  • Frequent watery stooles with little abdo pain
  • Rehydration mainstay of therapy
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9
Q

What toxins are involved in non-inflammatory diarrhoeal illness?

A

Cholera - ↑cAMP and C1 secretion

Enterotoxigenic E. coli

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10
Q

What is the mechanism of diarrhoea in cholera?

A

↑cAMP = loss of Cl, Na and K

Osmotic effect leads to massive water loss

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11
Q

What are the clinical features of inflammatory diarrhoeal illness?

A

Pain and fever - inflammatroy toxin damage and mucosal destruction
Bacterial infection/amoebic dysentery
Antimicrobials may be appropriate
Rehydration often sufficient

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12
Q

What must be assessed in a patient with gastroenteritis?

A

Symptoms and duration
Risk of food poisoning (Diet, contact, travel)
Assess hydration
Assess for inflammation (SIRS)

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13
Q

How is hydration assessed?

A 
Postural BP
Skin turgor
Pulse
Dry mouth
Sunken eyes/cheeks/fontanelle
Few/no tears
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14
Q

How severe can fluid loss be in gastroenteritis?

A

1-7L/day
80-100mmol Na+
Hyponatremia
Hypokalemia

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15
Q

How should a gastroenteritis patient be investigated?

A 
Stool culture
Blood culture
Renal function
Blood count - neutrophilia, haemolysis
Abdominal X-ray/CT
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16
Q

Haemolysis and gastroenteritis is associated with what?

A

E. coli O157

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17
Q

What is the DDx of gastroenteritis?

A

Inflammatory Bowel disease
Spurious/Overflow diarrhoea
Carcinoma
Sepsis

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18
Q

Diarrhoea and fever due to sepsis would likely present how?

A

Lack of abdominal pain/tenderness

No blood/mucus in stool

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19
Q

How is gastroenteritis diagnosed?

A

Rehydration therapy - salt/sugar

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20
Q

What post-infection sequelae are associated with Campylobacter gastroenteritis?

A

Guillain-Barre

Reactive arthritis

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21
Q

Why is dietery history unreliable in Campylobacter gastroenteritis?

A

Up to 7 days incubation

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22
Q

What tests can be used in stool testing?

A

Molecular detection

Antigen detection

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23
Q

What species are most common in Campylobacter gastroenteritis?

A

C. jejuni (90%)

C. coli (9%(

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24
Q

What is the most common source of Campylobacter gastroenteritis?

A

Chicken
Contaminated milk
Puppies

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25
Q

How does Salmonella gastroenteritis present?

A

Symptoms <48hrs
Diarrhoea <10 days
<5% +ve blood cultures
Positive stools up to 20 weeks

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26
Q

Prolonged Salmonella carriage is associated with what?

A

Gallstones

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27
Q

What post-infection sequelae is associated with Salmonella gastroenteritis?

A

Post-infectious irritable bowel

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28
Q

What species are most commonly responsible for Salmonella gastroenteritis?

A

S. enterica

S. bongori

29
Q

What tests are used for culturing salmonella?

A

Lactose non-fermenters
Antigen tests
Biochemical tests

30
Q

What are the most common salmonella isolates in the UK?

A

Salmonella enteritidis

Salmonella typhimurium

31
Q

Salmonella typhi and paratyphi are responsible for what?

A 
Enteric fever (not gastro-enteritis)
(Typhoid, Paratyphoid)
32
Q

What is E. coli O157 associated with?

A

Infection from contaminated meat or other people

33
Q

How does E. coli O157 present?

A

Illness with frequent bloody stools

Haemolytic-uraemic syndrome (HUS)

34
Q

What is the mechanism for E. coli O157 gastroenteritis?

A

Shiga toxin enters the blood, bacteria stays in gut

35
Q

Shiga toxin is produced by what pathogens?

A

E. coli O157

Shigella

36
Q

How does Haemolytic-uraemic syndrome (HUS) present?

A 
Renal failure 
Haemolytic anaemia
Thrombocytopenia
Bloody diarrhoea
Seizures
Abdominal pain
37
Q

How is Haemolytic-uraemic syndrome (HUS) treated?

A

Supportive - antibiotics not indicated
Dialysis
IVIG/Plasmapharesis

38
Q

Haemolytic-uraemic syndrome (HUS) is caused by what?

A

E. coli Shiga toxin

39
Q

What is the mechanism of Haemolytic-uraemic syndrome (HUS)?

A

Shiga toxin stimulates platelet activation, leading to microangiopathy

40
Q

Shigella is associated with what?

A

Gastroenteritis

41
Q

Which Shigella species are associated with Gastroenteritis?

A

S. sonnei - nursery outbreaks
S. flexneri
S. boydii
S. dysenteriae

42
Q

What are the less common cause of food poisoning outbreaks? What are their sources?

A 
Staph aureus (toxin)
Bacillus cereus (refried rice)
Clostridium perfringens (undercooked meat)
43
Q

When are antibiotics indicated in gastroenteritis?

A

Immunocompromised
Severe sepsis/invasion
Chronic illness

44
Q

How does C. diff diarrhoea present?

A

Previous history of antibiotics

Mild diarrhoea to severe colitis

45
Q

What antibiotics are associated with C. diff?

A 
"4 C's"
Clindamycin
Cephalosporins
Co-amoxiclav 
Ciprofloxacin
46
Q

What is the mechanism for C. diff diarrhoea?

A

Enterotoxin (A)

Cytotoxin (B)

47
Q

How is C. diff infection treated?

A 
Stop precipitating antibitics
Metronidazole
oral vancomycin (if >2 severity markers)
Fidaxomicin 
Stool transplants
Surgery
48
Q

How is C. diff infection prevented?

A 
Avoid prescribing broad-spec antibiotics
Avoid 4Cs
Antimicrobial management team policy 
Hygiene 
Patient isolation
49
Q

How are parasites diagnosed?

A

Microscopy:

Stool sample with “parasites, cysts and ova”

50
Q

What parasites are associated with gastroenteritis?

A

Protozoa

Helminths

51
Q

What protozoans are associated with gastroenteritis in the UK?

A

Giardia duodenalis (/lamblia)

52
Q

Giardia duodenalis gastroenteritis presents how?

A

Diarrhoea
Gas
Malabsorption
Failure to thrive

53
Q

How is Giardia duodenalis gastroenteritis diagnosed?

A

Cysts on stool microscopy
Duodenal biopsy
String test

54
Q

How is Giardia duodenalis gastroenteritis treated?

A

Metronidazole

55
Q

How is Giardia duodenalis gastroenteritis transmitted?

A

Direct contact with animals/people

Contaminated food/water

56
Q

How is cryptosporidium parvum gastroenteritis diagnosed?

A

Oocysts on microscopy

57
Q

Which UK protozoans are associated with gastroenteritis?

A

Cryptosporidium parvum
Giardia duodenalis
Entamoeba histolytica - imported

58
Q

How does cryptosporidium parvum gastroenteritis present?

A

Diarrhoea
N+V
Abdo pain

59
Q

How is cryptosporidium parvum gastroenteritis transmitted?

A

Animals

Contaminated water/food (9 cysts needed for infection)

60
Q

How is cryptosporidium parvum gastroenteritis treated?

A

None usually required

61
Q

How does Entamoeba histolytica infection present?

A

Amoebic dysentery
Invasive extraintestinal amoebiasis much later
Liver abscess
No bowel symptoms

62
Q

How is Entamoeba histolytica infection diagnosed?

A

Antibody detection

Stool microscopy “hot stool”

63
Q

How is Entamoeba histolytica infection treated?

A

Metronidazole

Luminal agent

64
Q

Which viruses are commonly associated with diarrhoea?

A

Rotavirus
Norovirus
Adenovirus

65
Q

How does Rotavirus present?

A

Children <5
Winter
Antigen in stool

66
Q

How does Norovirus present?

A

Vomiting and diarrhoea
Winter
Hospitals
Community centres

67
Q

How is Norovirus diagnosed?

A

PCR

68
Q

How is Norovirus managed?

A

Ward closure

Strict infection controls

3rd Year Infection (16 decks)

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