MB11 Gastrointestinal Infections 2 Flashcards Preview

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Flashcards in MB11 Gastrointestinal Infections 2 Deck (23):


•An 11-month-old baby girl is admitted to the paediatric unit with a 2-day history of fever, vomiting and copious watery diarrhoea. She was a full term normal delivery and has two siblings, one of whom had a mild diarrhoeal illness that cleared up 4 days earlier

•On examination she is unwell, mildly dehydrated, and febrile with a temperature of 38°C. her abdomen is soft, and there are no other findings of note.


1.What would be your immediate management of this baby?

2.What viral causes of diarrhoea are most likely?

3.How would a viral infection be diagnosed?

4.What is the natural course of infection?

  1. Looks like an infection. Probably a viral infection. Will need oral rehydration (if cant tolerate = IV) Needs to be nursed in a sideroom with relevant precautions
  2. Big Two are Rotavirus and Norovirus
  3. PCR and Electron Microscopy 

  4. Self - limiting infection, but where there is severe nutritional compromise there can be significant mortality associated


Learning Outcomes (for general perusal)

Be able to describe with examples:

1.Common intestinal parasites

2.Toxin-mediated food poisoning

3.Helicobacter pylori & gastric ulcer disease

4.Enteric fevers

5.Hepatitis viruses A & E


1) Common Intestinal Parasites

  1. What are the two main types of intestinal parasites?
  2. How are Protozoan infections usually diagnosed?
  3. How are Helminth (worm) infections diagnosed?

  1. Protozoans and Worms
  2. by microscopy for cysts or alternatively for trophozoite forms which are less commonly seen.

  3. by microscopy of faecal samples for ova (eggs) or actual worms (less common). 



What do these parasites cause?

  1. Cryptosporidium parvum

  2. Giardia lamblia

  3. Entamoeba histolytica

  1. Cryptosporidiosis

  2. Giardiasis

  3. Amoebic dysentery


Cryptosporidium parvum

  1. What does it cause?
  2. Who is it more serious for?
  3. How is it transmitted?
  4. How is it diagnosed?
  5. Who needs treatment?

  1. Cryptosporidiosis Moderate to severe diarrhea -self-limiting in immunocompetent

  2. in compromised host esp AIDS

  3. Transmission via drinking water contaminated by oocysts, from humans or animals - survives chlorination

  4. Special staining to see the oocysts. Or PCR

  5. only immunocompromised patients need treatment


Giardia lamblia

  1. What does it cause?
  2. How is it transmitted?

  1. Diarrhoea - usually no blood (most common in developing countries). Can cause chronic infection
  2. Water/food/ faecal oral


Entamoeba histolytica

  1. What does it cause?
  2. What can the trophozoites and cysts cause?
  3. How is it transmitted?

  1. Amoebic dysentery - diarrhoea, cramps - faeces contain mucus, blood and pus.
    1. Colonic ulcers 
  2. can invade liver and cause liver abscesses
  3. faecal contamination water/food, faeco-oral & sexual contact. 

    1. (from developing countries



Outline the main worms involved in intestinal infection

Enterobius – pinworm, very common (children)

Strongyloides – tropical areas, Bad in immunosupressed

Trichuris – Whipworm - tropical areas, causes anaemia

Hookworm – tropical, causes anaemia

Tapeworms - from raw meat


2) Toxin-mediated Food Poisoning

  1. Where does the toxin come from?
  2. What are the causes?


  1. Toxin is elaborated in food before its consumption

  2. A) Bacillus cereus

    B) Staphylococcus aureus

    C) Clostridium perfringens

    D) Clostridium botulinum (doesn't actually cause GI upset, same mechanism though)



2) A)                          Bacillus cereus

  1. What is type 1?
    1. What does it cause?
  2. What is type 2?
    1. What does it cause?

  1. organism grows in starchy food (esp fried rice),
    1. Vomiting 2–3 hours post ingestion. 
  2. organism grows in meat, vegetables, and sauces, producing a heat-labile enterotoxin.

    1. When ingested, the enterotoxin can cause profuse diarrhea 10–12 hours after ingestion of the toxin. 


2) B) Staphylococcal food poisoning

  1. What is it caused by?
  2. How does it cause infection?
  3. What are the symptoms and why?
  4. How long does recovery take?
  5. What does lab diagnosis involve?

  1. 8 enterotoxins (A-E) (a-food associated)
  2. Food contaminated by human carriers. Bacteria grow at room temperature & release heat- stable toxin

  3. Toxins -superantigens act on CNS to cause vomiting within  3 -6h, diarrhoea not a feature

  4. 24hours, no complications 

  5. detection of enterotoxin in food


2) C) Clostridium perfringens

  1. Where does it come from?
  2. What does it cause?

  1. GI tract of animals & the environment as spores

    Produces heat-resistant spores -survive cooking & grow if the cooked food is held between 10°C and 30°C for an extensive amount of time.

    Meat sauces & gravies are foods most frequently associated

  2. Watery diarrhoea


2) D) Botulism

Note: Vomiting and Diarrhoea are NOT caused 

  1. What is it caused by?
  2. How do the spores spread?
  3. What do it do in the body?
  4. What are the other forms?
  5. What does it present as clinically?
  6. What is the treatment?

  1. Clostridium botulinum
  2. Cl. Botulinum  spores germinate &  produce toxins under anaerobic conditions
  3. Toxin → peripheral nerve synapses →block neurotransmission
  4. Other forms : Infant botulism & wound botulism
  5. Clinically: flaccid paralysis → progressive muscle weakness & respiratory arrest
  6. When suspected, immediate antitoxin +  supportive care 


3) Helicobacter pylori & gastric ulcer disease

  1. What is H.Pylori?
  2. What is the pathogenesis? (how does it create pathological state?)
  3. How is it diagnosed?
  4. What is the treatment?

  1. (gram -ve spiral bacterium) -associated with > 90% of duodenal ulcers & 70-80% of gastric ulcers 
  2. Pathogenesis: disruption of gastric mucosa by a number of virulence factors:   cytotoxin, acid-inhibiting protein, adhesins, urease 

  3. –Histology of biopsy specimens

    –Urea breath test

    –Fecal H. pylori antigen testing 

  4. Combination therapy 
    1. Amoxicillin  +

      Clarithromycin  or


    2. Acid Suppressant


4) Enteric fevers: typhoid and paratyphoid

  1. What are these caused by?
  2. Where are they common?
  3. How do they spread?
  4. How are the bacteria transported around the body?
  5. When do patients develop a fever?
  6. What are the complications?
  7. How is it diagnosed?
  8. How is it treated?
  9. How can they be prevented?

  1. Caused by S. typhi, & paratyphi
  2. Developing countries
  3. Restricted to humans spread via contaminated food or water

  4. Bacteria multiply within, and are transported around, the body in macrophages

  5. After IP 10-14 days, patients develop sustained high fever, non-specific symptoms- rose spots more specific

  6. –Intestinal haemorrhage & perforation

    –Meningitis, osteomyelitis or endocarditis

    –Toxemia (e.g. myocarditis, hepatic and bone marrow damage)

    –1-3% of patients become chronic carriers 

  7. –Clinically, rose spots highly suggestive

    –Samples of blood, feces and urine cultured on selective media

    –Widal test –rising titer between acute and convalescent phase sera 

  8. immediate antibiotic (Ciprofloxacin/cefotaxime)

  9. involves public health measures, treating carriers & vaccination 


5) Viral hepatitis

  1. What is hepatitis usually caused by?
  2. What are the characterisitics of 
    1. Hep A + E
    2. Hep B, C, D?

  1.  Hepatitis is usually caused by viruses (eg. Hepatitis viruses A-E)
    1. Transmitted by fecal-oral route

      Do not result in a carrier state 

      Infections resolve 

    2. Transmitted by contaminated blood or sexually

      Chronic carrier 



5) A) Hepatitis A

(•only member of hepatovirus genus- endemic worldwide )

  1. Where does the virus spread to?
  2. How long is the IP?
  3. What are the main features?
  4. How is it diagnosed?
  5. How is it prevented?

  1. spreads to liver & replicates in hepatocytes 

  2. 4 weeks

  3. fever, anorexia, nausea & vomiting; jaundice common in adults

  4. HAV- IgM , Typing – PCR and sequencing 

  5. •pre- or post-exposure prophylaxis with human normal Igs  contain hepatitis A IgG

    •Inactivated viral vaccine



  1. What is useful for deciding if vaccination is necessary?
  2. What is the current vaccination program?

  1. •Hepatitis A IgG – useful for deciding if vaccination is necessary

  2. MSM vaccination program

    –Can be combined with hepatitis B as a single vaccine

(men who have sex with men)


Describe the Clinical and Virological Course of HAV


IP (incubation period) = 4 weeks 

HAV in faeces until 2 weeks

HAV IgM from week 1-4

IgG from week 1, peaks and remains highest by week 3

Shedding virus when you’re well for few weeks before symptoms. By the time you recognise a case, they will have already transmitted to others. 


What is the management of HAV?


  • No specific treatment – supportive
  • Contacts – can be given either
    • HNIG (human normal immunoglobulin)
    • HAV Vaccine
      • Depends on circumstances- level of contact. If outbreak. Timing etc.



  1. What is it?
  2. What is it caused by?
  3. What is the Incubation Period?
  4. For whom is it severe?
  5. How is it diagnosed?
  6. Is there a vaccine?
  7. How can it be zoonotic?
  8. What is a worry?

  1. Enteric, non-A-non-B hepatitis 

  2. •Caused by ssRNA virus- genus Hepevirus 

    •Sporadic & epidemic forms (Asia) 

  3. 6-8weeks. Generally mild

  4. pregnant women, mortality 20% during 3rd trimester due to fulminant hepatitis

  5. HEV-specific IgM

  6. No

  7. Food-bourne from pork. (undercooked pork)

  8. Far more common that thought to be (genotype 3)

    •Men over 50 predominantly                             •Can occasionally cause persistent infection with fibrosis in immunosupressed patients.


•A 29-year-old male presented with seven day history of fever, anorexia, right-sided abdominal discomfort, two days ago, he noticed that his urine became dark and a friend of him thinks he looks yellow.

•On examination, he was febrile, has yellow sclera and is tender in the right upper quadrant of his abdomen. Liver was slightly enlarged.

•Investigations: serum bilirubin and transaminases  raised.

•Viral serology demonstrated the presence of anti-HAV IgM antibodies. Other viral serological markers were absent.

What is the diagnosis of this condition and how can you manage this condition?


 Supportive management. Notification to public health. Is he a food handler? 

  • Contacts – can be given either
    • HNIG (human normal immunoglobulin)
    • HAV Vaccine