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Microbiology > Gastroenteritis > Flashcards

Gastroenteritis Flashcards

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Biology 101 flashcards
1
Q

Important questions to ask a patient with acute diarrhoea

A
  • Age
    • Under 40 – IBS, infective cause
    • Over 40- carcinoma
  • Duration – when where you last ill?
  • Consistency (british stool chart)
    • Watery/clear/frothy
    • Fluid/brown
    • Semiformed
    • Solid
    • Presence or absence of mucus or blood
  • Mucous (IBD/IBS)
  • Colour
    • Blood (fresh red blood, melaena)
    • Pale –steatorrhoea (biliary obstruction- gallstones/malignancy)
    • Black- Melaena
  • Urgency – IBD/IBS/Gastroenteritis
  • Duration
  • Frequency – How many times in 24 hour period? Day and night?
  • Accompanying symptoms (abdominal pain, fever, weight loss, tenensmus, vomiting, eye, skin or joint infections )
    • Systemic signs and symptoms: anaemia, pyrexia, arthritis, sacrolilitis, uveitis, erythema nodosum
    • Nausea and vomiting; dehydration
    • Abdominal pain
  • Foods consumed (food poisoning)
  • Drug history (antibiotics recent or current, anticoagulants, antiplatelet, laxatives)
  • Family history (IBD, occupation and travel history)
  • Recent travel- (travellers diarrhoea- pretravl vaccination, food and water precautions)
  • ill contact - important for viral gastroenteritis
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2
Q

Non infectious causes of diarrhoea

A
  • IBD
  • bowel cancer
  • diverticular disease
  • chronic ancreatitis
  • HIV
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3
Q

Acute diarrhoea

A

(lasting less than 14 days) with or without vomiting are due to gastrointestinal infection with bacteria, virus or protozoa.

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4
Q

Diarrhoea definition

A

defined as >300g of loose stool passed in a 24 hour period

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5
Q

Origin of infection

A

reflected in the nature of diarrhea:

  • Watery diarrhea – small intestine,
  • bloody diarrhea – Colonic mucosa
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6
Q

Bacterial causes of diarrhoea

A
  • Vibrio cholera
  • staphylococcus aureus
  • bacillus cerus
  • escherichia coli
  • clostridium perfringes
  • clostridium difficile
  • salmonella enteritidis
  • campylobacter
  • shigella
  • yesinio enterocolitica
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7
Q

Vibrio cholera

  1. organism
  2. transmission
  3. pathogenesis
  4. clinical features
  5. investigation
  6. treatment
A
  1. organism
    • Vibrio cholera (gram negative rods)
  2. transmission
    • Faecal oral route, particularly contaminated water
  3. pathogenesis
      • Exotoxin action
        • Exotoxin has two subunits (A and B)
        • B- binds to specific cell membrane receptors
        • A subunit activates intracellular enzyme adenylate cylase
        • Increased production of cAMO

Results in marked loss of water and electrolytes (sodium and chloride into the lumen of the small intestine)

  1. clinical features
      • Profuse watery diarrhea (up to 20 L/day)
        • “rice water stools”

Severe dehydration

  1. investigation
    • microscopy and culture of stool
  2. treatment
      • Intensive rehydration therapy and/or intravenous fluid replacement
        • Antibiotic therapy in severe (oral
        • tetracycline,doxycycline and ciprofloxacin)
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8
Q

Staphyoccocus aureus

  1. organism
  2. transmission
  3. pathogenesis
  4. clinical features
  5. investigation
  6. treatment
A
  1. organism
    • staphylococcus aureus
    • gram positive cocci
  2. transmission
    • eating contaminated foods
  3. pathogenesis
    • produces enterotoxins that induce severe vomititing and diarrhoea
  4. clinical features
      • rapid onset of symptoms (2-6 hours after eating)
        • Vomiting + Severe abdominal pain and diarrhea commonly not present
        • Symptoms are short lived, usually resolving within 12-24 hours
  6. investigation
    * Sample of suspected food required to look for the organism and for detection of the enterotoxin
  7. treatment
    * No specific treatment just supportive care as the illness is self-limiting
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9
Q

Bacillus cerus

  1. organism
  2. transmission
  3. pathogenesis
  4. clinical features
  5. investigation
  6. treatment
A
  • organism
    • bacillus cerus
    • gram positive bacillus
  • transmission
    • eating rice, occasionally pasta, meat and dairy products (survive cooking)
  • pathogenesis
    • food posiiong from the production of enterotoxins
  • clinical features
    • toxin production- rapid onset within 1-6 hours
    • vomitting then diarrhoea 8-12 hours
  • investigation
    • food and sample sent for microscopy and culture
  • treatment
    • self limiting
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10
Q

Escherichia coli

  1. organism
  2. transmission
  3. pathogenesis
  4. clinical features
  5. investigation
  6. treatment
A
  • organism
    • Ecoli, EPEC, ETEC, VTEX and EIEC
  • transmission
    • faecel oral route from contaminated food
  • pathogenesis- four types
      • EPEC- attaches to and damages the intestinal villi directly. Children <2 years
        • ETEC: enterotoxin, acts on cAMP in a similar manner to cholera and causes travelers diarrhea
        • VTEC: possesses a toxin, like shigella toxin, that acts locally on the mucosa to cause a haemorrhagic colitis or systemically resulting in haemolytic uraemic syndrome
        • EIC – invades the mucosa in a manner similar to shigella
  • clinical features
      • Water diarrhea – ETEC
        • All other types – bloody diarrhea

Pain can be associated with bloody diarrhea

  • investigation
    • stool microscopy and cultures and serotyping
  • treatment
    • supportive therapt with ORS
    • antibitoics reserved for severe, when ciprofloxacin is the drug of choice
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11
Q

Clostridium perfringes

  • organism
  • transmission
  • pathogenesis
  • clinical features
  • investigation
  • treatment
A
  • organism
    • clostridium perfringes
  • transmission
    • Commensal of the colon, meat can become contaminated with spore and are able to stand boiling. If the meat is then left at room temperature the spores germinate and replication occurs
  • pathogenesis
      • Produces an enterotoxin
        • Toxin induces diarrhea

Enterotoxin is not able to reproduce in food, only after injestion

  • clinical features
      • 8-24 hours after injestion
        • Explosive watery diarrhea
        • cramping and abdo pain
  • investigation
    • microscopy and culture of food and faeces
  • treatment
    • supportive therapy with ORS
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12
Q

clostridum difficile

  • organism
  • transmission
  • pathogenesis
  • clinical features
  • investigation
  • treatment
A
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13
Q

Salmonella enteridis

  • organism
  • transmission
  • pathogenesis
  • clinical features
  • investigation
  • treatment
A
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14
Q

Campylobacter

  • organism
  • transmission
  • pathogenesis
  • clinical features
  • investigation
  • treatment
A
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15
Q

Shigella

  • organism
  • transmission
  • pathogenesis
  • clinical features
  • investigation
  • treatment
A
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16
Q

Viral causes of gastroenteritis

A
17
Q

Protozoal causes of diarrhoea

A
18
Q

Investigations

A
  • Look for :
    • dry mucous membranes, decreased skin turgour, capillary refil >2secs
    • fever,, weight loss, clubbing, anaemia, oral ulvers
  • rectal exam for masses or impacted faeces
  • FBC:
    • MCV decrease/Fe deficiency eg coeliac or colon,
    • MCV Increase if alcohol abuse or B12 absorption decreased
    • ESR/CRP – infection
    • U&E: K decrease if severe d & V
    • TSH: throtoxocis
    • Coeliac serology
  • Stool MC & S: Bacterial pathogens, parasities
  • Rigmoid sigmoidoscopy – with biopsy of normal and abnormal looking mucosa
  • Colonoscopy/barium enema
19
Q

Management

A
  • Treat causes
  • Food handlers: no work until stool samples negative
  • Hospital outbreak- isolation
  • Oral rehydration is better than IV but if impossible (0.9% saline + 20mmol K+/L IVI
  • Codeine phosphate 30mg/8hr to decrease stool frequency
  • Avoid antibitotics unless infective diarrhea is causing systemic upset

Microbiology (21 decks)

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