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Infection > Diarrhoea > Flashcards

Diarrhoea Flashcards

1
Q

how do the definitions between diarrhoea and gastroenteritis differ?

A

Diarrhoea - subjective
fluidity and frequency

Gastro-enteritis - objective
three or more loose stools/day
accompanying features

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2
Q

what is dysentery?

A

large bowel inflammation, bloody stool

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3
Q

what is the bristol stool chart?

A
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4
Q

what is the epidemiology of gastroenteritis?

A

Contamination of foodstuffs
- Intensively farmed chicken and campylobacter

Poor storage of produce
Bacterial proliferation at room temperature

Travel-related infections e.g. Salmonella

Person-to-person spread
norovirus

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5
Q

what is the most common foodborn pathogen?

A

Campylobacter

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6
Q

what pathogen causes the most hospital admissions?

A

Salmonella

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7
Q

what is the food linked to most cases of food poisoning?

A

Poultry meat

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8
Q

what defences do we have against enteric infections?

A

stomach acidity
antacids and infection

normal gut flora
Cl. difficile diarrhoea

immunity
HIV + salmonella

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9
Q

what are clinical features of non inflammatory/secretory diarrhoea?

A

secretory toxin-mediated
cholera - increases cAMP levels and Cl secretion
enterotoxigenic E. coli (travellers’ diarrhoea)

frequent watery stools with little abdo pain

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10
Q

what is the mainstay of treatment for secretory/inflammatory diarrhoea?

A

rehydration

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11
Q

what is the cause of non inflammatory/secretory diarrhoea?

A

cholera

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12
Q

what is the mechanism of diarrhoea in cholera?

A

Increased cAMP results
in loss of Cl from cells
along with Na and K

Osmotic effect leads to
massive loss of water from
the gut

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13
Q

what are the clinical features of inflammatory diarrhoea?

A

inflammatory toxin damage and mucosal destruction pain and fever
bacterial infection / amoebic dysentery

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14
Q

what is the choice of treatment for inflammatory diarrhoea?

A

antimicrobials may be appropriate but rehydration alone is often sufficient

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15
Q

what is the cause of inflammatory diarrhoea?

A

shigella dystentry

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16
Q

how should a patient with diarrhoea be assessed?

A

Symptoms and their duration
>2/52 unlikely to be infective gastro-enteritis

Risk of food poisoning
Dietary, contact, travel history
assess hydration

postural BP, skin turgor, pulse

features of inflammation (SIRS)
fever, raised WCC

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17
Q

what would be seen in an infant with diarrhoea?

A
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18
Q

what fluid and electrolyte losses result from secretory diarrhoea especially?

[1-7 l fluid per day containing 80-100 mmol Na]

A

Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions

Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)

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19
Q

what investigations should be done for a patient with diarrhoea?

A

stool culture +/- molecular or Ag testing

blood culture

Renal function

blood count - neutrophilia, haemolysis (E. Coli O157)

abdominal X-Ray/CT if abdomen distended, tender

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20
Q

what are differential diagnosis for diarrhoea?

A

Inflammatory bowel disease
Spurious diarrhoea -secondary to constipation
Carcinoma

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21
Q

Diarrhoea and fever can occur with sepsis outside the gut, what might be clues for this differential diagnosis?

A

lack of abdo pain/tenderness
goes against gastroenteritis
no blood/mucus in stools

22
Q

what is the treatment for gastro-enteritis?

A

Rehydration - iv or oral?

Oral rehydration with salt/sugar solution
iv saline

23
Q

what is campylobacter gastroenteritis, and what is associated with it?

A

Up to 7 days incubation so dietary history may be unreliable

Stools negative within 6 weeks

abdominal pain can be severe

<1% invasive
Post-infection sequelae
Guillain-Barre syndrome, Reactive arthritis

24
Q

what routine bacterial cultures are available?

A

selective and enrichment methods of culture necessary - variety of media and incubation conditions

takes 3 days to complete all tests

[molecular and antigen detection]

25
Q

what are the two spaces of campylobacter that cause most infections?

A

specialised culture conditions

Two species cause most infections:
C. jejuni (90%)
C. coli (9%)

26
Q

what is salmonella gastroenteritis and what is associated with it?

A

symptom onset usually <48 hrs after exposure

diarrhoea usually lasts <10 days

<5% positive blood cultures
20% patients still have positive stools at 20/52
Prolonged carriage may be associated with gallstones

Post-infectious irritable bowel is common

27
Q

what is the routine bacterial culture for salmonella?

A

2 species in genus: S.enterica S.bongori

> 2500 serotypes with individual names - most are S.enterica species
traditionally named after place of first isolation eg Sandiego, Panama, Derby
screened out in lab as ‘lactose non-fermenters’ – look alike microscope - then antigen (O and H) and biochemical tests

28
Q

what are the most common salmonella infections in the UK?

A

Salmonella enteritidis and Salmonella typhimurium

29
Q

what is ecoli?

A

Infection from e.g. contaminated meat or person-to-person spread (low incoulum)
Typical illness characterised by frequent bloody stools

E. coli O157 produces Shiga toxin (same toxin also produced by Shigella spp) (previously called verocyto- toxin)
E. coli O157 stays in the gut but the toxin gets into the blood

toxin can cause hemolytic-uraemic (HUS) syndrome (haemolytic anaemia and renal failure)

30
Q

what is HUS characterized by?

A

renal failure, haemolytic anaemia and thrombocytopenia. Treatment supportive – antibiotics NOT indicated

31
Q

what is the mechanism behind HUS?

A

Toxin stimulates
platelet activation

micro-angiopathy results

32
Q

what are different species of shigella?

A

(4 species S. sonnei, S.flexneri, S.boydii, S. dysenteriae) – outbreaks of Shigella sonnei in children’s nurseries

33
Q

what are other forms of ecoli?

A

enteroinvasive
enteropathogenic
enterotoxic (traveller’s diarrhoea)

34
Q

what can occasionally cause outbreaks of food poisoning?

A

Staph aureus (toxin)
Bacillus cereus (re-fried rice)
Clostridium perfringens (undercooked meat/cooked food left out - toxin accumulates in spore formation)

35
Q

when are antibiotics indicated?

A

Indicated in gastroenteritis for
immunocompromised
severe sepsis or invasive infection
chronic illness e.g. malignancy

Not indicated for healthy patient with non-invasive infection

36
Q

what is clostridiodes difficile diarrhoea?

A

Patient usually gives history of previous antibiotic treatment – the “4 C antibiotics”
Severity ranges from mild diarrhoea to severe colitis
C. Diff produces enterotoxin (A) and cytotoxin (B) (inflammatory)

37
Q

what is clostridiodes difficile treated with?

A

metronidazole
oral vancomycin
Fidaxomicin (new and expensive)
Stool transplants
surgery may be required

38
Q

how is CDI prevented?

A

Reduction in broad spectrum antibiotic prescribing
Avoid 4 Cs – cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin
Antimicrobial Management Team (AMT) and local antibiotic policy
Isolate symptomatic patients
Wash hands between patients (spores resist alcohol rubs) – contact precautions
Cleaning environment

39
Q

how is CDI managed?

A

Stop precipitating antibiotic (if possible)

Follow published treatment algorithm – oral metronidazole if no severity markers

Oral vancomycin if 2 or more severity markers

40
Q

how are parasites diagnosed?

A

Protozoa and helminths

Diagnosis generally by microscopy

Send stool with request “parasites, cysts and ova please” or P, C and O

41
Q

what are examples of UK parasites?

A

Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites

Cryptosporidium parvum

42
Q

what symptoms are caused by Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites?

A

diarrhoea, gas, malabsorption, failure to thrive

43
Q

how are Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites
transmitted?

A

direct contact with cattle/cats/dogs/other people
food/water contaminated with faeces

44
Q

how are Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites diagnosed?

A

Cysts seen on stool microscopy
Trophozoites – duodenal biopsy ‘tightly bound to villi’ or string test

45
Q

what is mechanism of transmission for protozoa?

A

Carried by >150 species of mammals (cats/dogs/cattle/deer/rabbits…)
20 species known to infect humans
Diarrhoea, nausea and vomiting, abdo pain
Infected animals/faeces - contaminated water /food – need only 9 oocysts for infection (a stool = 1 million)

46
Q

how is Cryptosporidium parvum diagnosed?

A

oocysts seen on microscopy

47
Q

how is Cryptosporidium parvum treated?

A

no specific treatment usually required

48
Q

ntamoeba histolytica
amoebic dysentery (instestinal amoebiasis)
Invasive extraintestinal amoebiasis (liver/pleuropulmonary/brain abscess) – months/years later – usually no bowel symptoms

A

Microscopy: trophozoites in symptomatic patient - “hot stool”; asymptomatic patient-cysts seen in formed stool
Antibody detection (serum) – for invasive disease
Intestinal disease: metronidazole + luminal agent to clear colonization

49
Q

liver abscess pus known as?

A

amoebic liver abscess - long term complication (“anchovy pus”)

50
Q

rotavirus

A

Rotavirus in children under 5 yrs
common in winter – previously estimated 55000 cases/yr Scotland
1465 laboratory reports in Scotland in 2011
diagnosis by antigen detection in stool
rotavirus vaccine introduced July 2013 in UK, 8+12 weeks

51
Q

norovirus?

A

diagnosis by PCR
very infectious -18 virus particles (1g stool=5 billion infectious doses)
ward closures common – staff and patients affected
strict infection control measures needed

Noroviruses - previously known as
small round structured viruses (SRSV)
Norwalk like viruses (Norwalk,Ohio)
Winter vomiting disease – diarrhoea and vomiting
common cause of outbreaks
Institutions: hospital, community (schools, care homes), cruise ships
In Scotland between 1.5 and 3.5 thousand cases/year

Infection (14 decks)

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