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Infection > Infectious Diarrhoea > Flashcards

Infectious Diarrhoea Flashcards

1
Q

Define diarrhoea

A

Fluidity and frequency

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2
Q

Define gastro-enteritis

A

3+ loose stools/day & accompany features

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3
Q

Define dysentery

A

Type of GE
Large bowel inflammation
Bloody/mucusy stools
(& fever, abdo pain etc.)

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4
Q

Define chronic diarrhoea

A

Diarrhoea lasting for more than 14 days

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5
Q

What may cause GE?

A

Contamination of foodstuffs, e.g. campylobacter and chicken
Poor storage, e.g. bacterial proliferation at room temperature
Travel related infections, e.g. salmonella
Person to person spread, e.g. norovirus

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6
Q

What is the most common cause of GE?

A

Viruses

Most common bacterial cause in UK: campylobacter

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7
Q

What are our natural defences against GE?

A

Hygiene, stomach acidity, normal flora, immunity

NB - therefore antacids, and those with HIV are at greater risk of GE

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8
Q

What are two non-inflammatory diarrhoeas?

A

Cholera and enterotoxogenic E. coli (traveller’s diarrhoea)

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9
Q

Describe the mechanism by which cholera vibrio causes diarrhoea

A

Releases a toxin which is endocytosed by enterocytes Via G5, the toxin stimulates adenylyl cyclase which increases the levels of cAMP
cAMP activates the CFTR channel –> efflux of Cl –> efflux of water and other ions

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10
Q

Describe the mechanism by which enterotoxogenic E. coli causes diarrhoea

A

Toxin, via G5 stimulates adenylyl cyclase –> increased cAMP levels –> increased chloride secretion –> increased water secretion

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11
Q

Give an example of an inflammatory diarrhoea

What happens in inflammatory diarrhoea?

A

Shigella/amoebic dysentry
(which causes bloody diarrhoea, pain and fever)

Inflammatory toxin damage and mucosal destruction

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12
Q

Symptom duration >2/52 is likely to be what?

A

Unlikely to be infective GE

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13
Q

What questions do you need to ask in a history of suspected infective GE?

A

Dietary, contact, travel history

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14
Q

How could you assess a patient with diarrhoea for dehydration?

A

Postural BP, skin turgor, pulse

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15
Q

What are signs of dehydration in children?

A

Sunken fontanelle, few/no tears, dry mouth/tongue, decreased skin turgor, sunken eyes/cheek/abdomen

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16
Q

What must you also assess the patient for?

A

Features of inflammation - SIRS (fever, raised WCC)

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17
Q

What complications are associated with diarrhoea?

A

Hyponatraemia, hypokalaemia, normal anion gap metabolic acidosis, severe fluid loss

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18
Q

How do you investigate suspected infective GE?

A 
Stool culture 
Blood culture
Renal function 
FBC - neutrophilia, haemolysis
Abdo X-Ray 
Suspected parasite: microscopy (e.g. send stool with request such as parasites, cysts and ova)
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19
Q

What are potential differentials for GE?

A

IBD/IBS
Spurious diarrhoea
Carcinoma
Due to sepsis outside the gut

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20
Q

How do you manage GE?

A

Rehydration is mainstay
Salt and sugar solution if oral
IV saline

21
Q

What are the bacterial causes of diarrhoea?

A 
Campylobacter 
Salmonella
E. coli 
Shigella 
Staph aureus
Bacillus cereus
22
Q

Campylobacter GE

A

Up to 7 day incubation period
Abdo pain
Flu like predrome
Post-infection sequelae: GB syndrome, reactive arthritis

Caused by: C. jejuni, C. coli
Sources: chicken

23
Q

Salmonella GE

A

Symptom onset <48h post exposure
Diarrhoea lasts <10 days
Prolonged carriage assoc. w. gallstones
Post infectious IBS common

Caused by: s. enterica spp (s. enteritidis, a. typhidmurium)
50% from abroad

24
Q

E. coli 0157

A

Contaminated meat/person to person spread
Frequent bloody stools
Produces verocytotoxin which enters blood and may cause HUS

25
What is HUS?
Haemolytic uraemic syndrome Triad of: haemolytic anaemia, thrombocytopenia and AKI Caused by toxin binding to globotriasolyceramide on glomerulus --> actives platelets --> thrombotic microangiopathy (microthrombi occlude arterioles/capillaries)
26
How do you test for salmonella GE?
Screened as lactose non-fermenters, then antigen and biochemical tests
27
How do you treat HUS?
Antibiotics not indicated
28
Shigella
Outbreaks of shigella sonnei in nurseries | Causes bloody diarrhoea, ab pain and vomiting
29
Bacillus cereus
Two patterns seen: - Vomiting within 6h usually due to rice - Diarrhoeal illness after 6h
30
When are antibiotics indicated in the treatment of GE?
``` Immunocompromised Severe sepsis/invasive infection Valvular heart disease Chronic disease Diabetes ```
31
Clostridium difficle
Recent antibiotic use (esp. 4 Cs) Severity variable: mild diarrhoea --> severe pseudomembranous colitis (inflammation of the large bowel due to C. diff overgrowth) C. diff produces endotoxin A and cytotoxin B
32
How do you treat C. diff infection?
1. stop precipitating antibiotics (clarithromycin, clindamycin, co-amoxiclav, cephalosporins) 2. oral metronidazole (if no severity markers) 3. oral vancomycin (if 2+ severity markers) 4. fidamoxicin 5. stool transplant 6. surgery
33
How can we prevent c. diff infections?
Reduce broad spectrum antibiotic use Antimicrobial management team and local antibiotic policy Isolate symptomatic patients Wash hands b.w patients
34
Giardia Lamblia
Contaminated water Diarrhoea, malabsorption, failure to thrive Non-bloody diarrhoea, that comes on gradually and can last a long time UK parasite Vegetative form in duodenal biopsy/string test (swallow capsule that extends string from mouth to top of duodenum, pulled back out and examined under microscopy) Two forms of GL: dormant (cysts), trophozites (active)
35
How do you treat giardia lamblia?
Metronidazole
36
Cryptosporidium parvum
HIV/immunocompromised Contaminated water/animal faeces Cysts on microscopy Supportive Rx
37
Amoebic dysentry
Blood diarrhoea, lasts quite long Vegetative form in symptomatic patient (hot stool) Cysts in asymptomatic patient Complications: amoebic liver abscess (which produces anchovy pus)
38
How do you treat amoebic dysentery?
Metronidazole
39
Rota virus
Under 5s Common in winter Dx: antigen detection Vomiting, non-bloody diarrhoea
40
Adenovirus
Certain strains can cause diarrhoea
41
Norovirus
Winter, vomiting bud Common cause of outbreaks (hospital, nursing homes etc.) Dx: PCR V. infectious - strict ICP controls req.
42
Define travellers diarrhoea
3+ loose stools in 24h with/without 1+ of: ab cramps, fever, nausea, vomiting, blood in stools
43
What is the commonest cause of traveller's diarrhoea?
E. coli
44
What is acute food poisoning?
Sudden onset N, V and diarrhoea after ingestion of a toxin
45
What tends to cause acute food poisoning?
Staph aureus Bacillus cereus Clostridium perfringes
46
Staph aureus diarrhoea
Severe vomiting | Short incubation period
47
What are the incubation periods for: a. Staph aureus, bacillus cereus b. Salmonella, E. coli c. Shigella, campylobacter d. Giardiasis, Amoebiasis?
a. 1-6h b. 12-48h c. 48-72h d. >7 days
48
What organism causes giardiasis?
Flagellated protozoan giardia lamblia
49
How is Giardia lamblia spread?
Faecal oral route

Infection (22 decks)

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