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GI Infections Flashcards

1
Q

Describe the stages of pathogenic infection?

A
  • Exposure
  • Adhesion
  • Invasion
  • Colonization
  • Toxicity
  • Tissue damage and disease
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2
Q

What is the difference between colonisation and infection?

A

Colonisation
- establishment of a microorganism on or within a host which does not cause symptoms

Infection
- invasion of a host causing the patient to be symptomatic

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3
Q

What is virulence?

A

likelihood of a pathogen to cause disease

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4
Q

What normal bacterial flora is found in the mouth?

A 
Strep. “viridans”
Neisseria sp.
Anaerobes
Candida sp. (few)
Staphylococci
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5
Q

Why are the stomach and duodenum usually sterile?

A
  • Low (acidic) pH

- Few Candida & Staphylococci may survive

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6
Q

What normal bacterial flora are found in the small intestine?

A

Lactobacilli
E-Coli
Enterococcus

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7
Q

The colon normally contains what types of bacteria?

A

Large numbers of coliforms and anaerobes

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8
Q

The bile ducts are usually sterile. TRUE/FALSE?

A

TRUE

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9
Q

How are GI infections caused in the community?

A
  • Cross-contamination of work surfaces/utensils
  • Undercooking (insufficient heat to kill pathogens/ inadequate defrosting of frozen food)
  • Improper storage of food (inadequate refrigeration)
  • Poor reheating of food
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10
Q

Describe how CDiff infection is caused?

A
  • C diff. is present in small numbers in bowel
  • Infection occurs when antibiotics kill off normal competitive bowel flora
    => C diff overgrows
  • Organism produces spores that are more resistant to disinfectants
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11
Q

What symptoms do patients experience with C Diff?

A
  • Diarrhoea (sometimes bloody)
  • abdominal pain
  • Severe cases may progress to pseudomembranous colitis or bowel perforation
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12
Q

How is C Diff usually managed?

A

Less severe = oral metronidazole

Severe = oral vancomycin

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13
Q

How is C Diff. prevented?

A
  • Use narrow spectrum antibiotics where possible
  • Avoid the “4Cs”
  • Isolation of patients
  • HandWASHING (not alcohol gel)
  • Cleaning of the environment
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14
Q

If there is not one good lab test for CDIff, how can it be confirmed?

A
  • Screening test for presence of the organism (GDH)
  • If GDH positive, test for Toxins (A&B)

Culture can be done if strain needs to be typed:
- Only used if an outbreak is expected OR if hyper toxin-producing strains

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15
Q

What viruses commonly cause diarrhoea?

A

Rotavirus

Norovirus

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16
Q

Rotavirus usually presents in patients of what age?

A
  • commonest cause of diarrhoea in patients under 3

- most cases occur in children <5 years

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17
Q

How is rotavirus spread?

A
  • Person-person spread

- direct or indirect

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18
Q

Patients with rotavirus diarrhoea often have blood in their stool. TRUE/FALSE?

A

FALSE

no blood is seen

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19
Q

What complications can rotavirus cause?

A

Children may develop post-infection malabsorption

=> causing more diarrhoea

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20
Q

How is rotavirus diagnosed?

A

PCR test on faeces

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21
Q

How is rotavirus managed?

A

Rehydration is key (orally where possible)

- vaccines given at 2 and 3 months of age

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22
Q

Why should the rotavirus vaccine not be given >3 months of age?

A

Risk of intussusception

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23
Q

How is norovirus spread and when does it normally present?

A
  • “winter diarrhoea and vomiting disease”
    SPREAD VIA:
  • faecal-oral/droplet
  • person to person (or on contaminated food/water)
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24
Q

Exposure to a low dose can infect patient’s with norovirus. TRUE/FALSE?

A

TRUE

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25
Q

Describe the disease course of norovirus

A
  • Short incubation – often <24 hours

- Sudden onset explosive D and V, lasts 2-4 days

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26
Q

How is norovirus diagnosed?

A
  • Faeces specimen or vomit swab for PCR test
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27
Q

How is norovirus treated?

A
  • Rehydration is key, esp. in the young and elderly
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28
Q

Patients can spread norovirus after their symptoms have disappeared. TRUE/FALSE?

A

Asymptomatic shedding occurs for up to 48 hours post cessation of symptoms

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29
Q

Where are outbreaks of norovirus common?

A
  • Hospitals,
  • Schools
  • Cruise ships
  • Nursing Homes
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30
Q

Which infections need patients to be contained in a side room?

A

C difficile and norovirus

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31
Q

Which infections require patients to be admitted to the infectious diseases unit?

A

Salmonella

E-Coli 0157

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32
Q

What puts patients at a higher risk of developing a GI infection?

A
  • Malnutrition
  • Exposure to contaminated food/water /travel
  • Winter congregating/ summer floods
  • Age <5 or elderly
  • not breastfeeding
  • Acid suppression
  • Immunosuppression
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33
Q

What is the definition of diarrhoea?

A

> 3 unformed stools/day
From no other cause (laxatives etc)
Stool holds the shape of container
Departure from normal bowel habit

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34
Q

What pathogens are known to cause “dysentry” i.e inflammation of the colon?

A
  • Shigella, Campylobacter
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35
Q

What symptoms do patients experience with gastroenteritis?

A
  • inflames intestine
  • diarrhoea associated with blood and mucus
  • fever
  • abdominal pain
  • rectal tenesmus (sense of incomplete defaecation).
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36
Q

How long does gastroenteritis normally last?

A

Acute is duration < 2 weeks

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37
Q

What can go wrong in the kitchen that may cause a gastroenteritis?

A
  • cross contamination of raw and cooked food
  • preparation of food too far in advance
  • inadequate heating and cooling
  • contaminated environment/ equipment
  • poor personal hygiene
38
Q

What factors should be asked about in a gastroenteritis infection history?

A
  • foreign travel
  • antibiotics
  • camping
  • raw seafood
  • anal receptive sex (MSM)
  • HIV status
  • cruise ship
39
Q

What infections have a short incubation period?

A

Bacillus cereus (Gm +ve bacillus)

  • forms Heat resistant spores
  • usually from Reheated rice

Staph. Aureus (Gm +ve coccus)

  • preformed toxin in food
  • found in foods left at room temp. (Milk/ meat/fish)
40
Q

What infections are tested for on a normal stool sample?

A
  • All stools get Salmonella/Shigella/Campylobacter/ E-Coli 0157 & cryptosporidium
  • All > 4 yrs stools get C Diff
41
Q

Shigella infection produced Shiga Toxin, but what does this do?

A
  • Binds to receptors found on renal cells, RBC’s & others
  • Inhibits protein synthesis
  • Causes cell death
42
Q

Type 2 is more potent than type 1 in Shigella. TRUE/FALSE?

A

TRUE

43
Q

Shiga-like toxins have been discovered in other types of bacteria. TRUE/FALSE?

A

TRUE

>30 serotypes of E- coli produce Shiga –like toxins

44
Q

How do shiga-like toxins produced by ecoli cause damage?

A
  • inhibit protein synthesis

- kill enterocytes

45
Q

What happens after shiga-like toxins attack the bowel?

A
  • toxins are carried to the kidneys
  • causes haematuria and renal failure (Haemolytic Uraemic Syndrome)
  • shiga-like toxin 2 causes this
46
Q

What symptoms/exposure would make you consider EColi 0157 infection?

A
  • bloody diarrhoea
  • exposure to beef (raw milk/water)
  • animal contact
  • children + elderly
47
Q

HOw does haemolytic uraemic syndrome usually present?

A
  • Abdo pain
  • fever
  • pallor
  • petechiae
  • oliguria
  • bloody diarrhoea in 90% of cases
  • 85 of cases occur in those under 16 years old
48
Q

Describe how a patient’s blood results may look in haemolytic uraemic syndrome?

A
  • High white cells
  • Low platelets
  • Low Hb
  • LDH>1.5 x normal
49
Q

How is haemolytic uraemic syndrome investigated?

A
  • stool culture (all Pts with bloody faeces)
  • FBC, U+E, Blood film, Clotting
  • LFT
  • urine (dipstick/micro)
  • lactate
50
Q

What drugs should NOT be given if you suspect a patient has haemolytic uraemic syndrome?

A

NO antibiotics: may precipitate HUS
NO anti-motility agents
NO NSAIDS

51
Q

What can be used to “type” EHEC? (a strain of EColi which produces shiga-like toxin)

A
  • McConkey agar/ Sorbitol McConkey agar
  • Antisera for serotypes
  • ELISA identifies toxins
52
Q

What tropical infections can present in the GI tract?

A
  • Acute traveller’s diarrhoea
  • Enteric fever
  • Fever and Jaundice
  • Protozoan infections
  • Helminthic Infections
53
Q

What questions should you remember to ask a returned traveller if you suspect a Tropical GI infection?

A
  • Where have they been? (Rural/urban area)
  • Accommodation? (air conditioning)?
  • When did they get back?/ When did symptoms start?
  • Insect/Tick bites
  • Symptoms?
  • Anyone else unwell?
  • Activities whilst away? (Swimming/water sports/animal contact/bat caves/walking in bush/sex/work)
  • Precautions? (Vaccinations/malaria prophylaxis/bite protection/condoms)
54
Q

What signs should you look for on examination of a returned traveller?

A
  • Fever
  • Rash
  • Hepatosplenomegaly
  • Lymphadenopathy
  • Insect bites
  • Wounds
55
Q

Which infections of the returned traveller can cause a fever?

A
  • Respiratory tract infections – pneumonia/influenza
  • Traveller’s diarrhoea
  • Malaria
  • Enteric fever (typhoid/paratyphoid fever)
  • Arboviruses – e.g. Chikungunya/Zika
56
Q

What is the definition of Traveller’s diarrhoea?

A

3 loose stools in 24 hrs

- usually associated with fever

57
Q

What can cause Traveller’s diarrhoea?

A
  • Ecoli most common
  • salmonella, campylobacter and shigella
  • on Cruise Ships Norovirus/Rotavirus = common
58
Q

What is the most likely cause of profuse watery diarrhoea as opposed to the bloody diarrhoea usually experienced in Ecoli infection?

A

Cholera

- common in refugee camps

59
Q

How is Acute Traveller’s diarrhoea investigated?

A
  • Stool culture

- Stool wet prep on recently passed stool for amoebic trophozoites

60
Q

How is Traveller’s Diarrhoea treated?

A
  • Supportive – fluid rehydration (oral/IV)
  • In those travelling a fluoroquinolone (ciprofloxacin) single dose can stop worsening
  • Antibiotic resistance – now very common (if pt has been travelling in Asia, a macrolide e.g. azithromycin may be useful)
61
Q

What are the causes of enteric fever?

A

Typhoid or paratyphoid fever

Salmonella typhi or paratyphi

62
Q

Patients with enteric fever usually return from travelling in what part of the world?

A

Most common in those returning from Indian subcontinent and SE Asia

63
Q

What is the normal incubation period for enteric fever?

A

7-18 days (though occasionally up to 60 days)

64
Q

Patients with enteric fever usually present with what symptoms?

A
  • Fever
  • Headache
  • Constipation or diarrhoea
  • Dry cough
65
Q

What are the potential complications of enteric fever?

A
  • GI bleeding
  • GI perforation
  • Encephalopathy
  • Bone and joint infection
66
Q

How is enteric fever treated empirically if the patient has signs of sepsis?

A

IV Ceftriaxone

67
Q

What antibiotics can be used to treat enteric fever and how long do they take to clear the fever?

A

Ciprofloxacin <4 days (70% of cases are now resistant!)
Azithromycin 4.4 days
Ceftriaxone 6.2 days

68
Q

What infections can cause pre-hepatic (haemolytic) jaundice?

A

(i. e. jaundice from breakdown of red blood cells)
- Malaria
- HUS as complication of diarrhoea – E.coli 0157
- Sickle cell crisis triggered by infection

69
Q

What infections can cause hepatic jaundice?

A
  • Hepatitis A and E – acute (occasionally Hep B)
  • Leptospirosis – Weils diseases
  • Malaria
  • Enteric fever
  • Rickettsia (scrub typhus, Rocky Mountain spotted fever etc)
  • Viral haemorrhagic fever
70
Q

How is fever and jaundice investigated in a returned traveller?

A
  • Malaria blood film and rapid antigen
  • Blood film for red cell fragmentation
  • Blood tests and cultures
  • US abdomen
  • Serology for viruses
71
Q

How is fever and jaundice treated in a returned traveller?

A
  • Appropriate isolation and infection control procedures
  • Supportive – possible dialysis if AKI
  • Acute liver failure – hepatology/transplant unit
72
Q

What is a Amoebiasis infection caused by and how is this spread?

A
  • caused by a protozoa
  • faecal-oral spread
  • strong association with poor sanitation
73
Q

Patients can carry amoebiasis infection asymptomatically. TRUE/FALSE?

A

TRUE

- may not be symptomatic but protozoa chronically sheds cysts in stools

74
Q

What symptoms are caused by amoebiaisis infection?

A
  • Abdominal pain/ Peritonism
  • Fever
  • Bloody diarrhoea / colitis (can perforate)
75
Q

What investigations are used for suspected amoebiasis?

A
  • Stool microscopy for trophozoites/ cysts
  • AXR if you suspect toxic megacolon
  • Endoscopy for biopsy (not if evidence of toxic dilatation)
76
Q

What complication can amoebiasis infection cause?

A

Liver abscesses

77
Q

How long do amoebic liver abscesses take to present and in which gender are they most common?

A
  • more common in men
  • incubation period 8-20 weeks
  • usually present sub-acutely over 2-4 weeks
78
Q

What symptoms are caused by an amoebic liver abscess?

A
  • Fever, sweats
  • Upper abdominal pain
  • Sometimes history of GI upset (dysentery)
  • Hepatomegaly
  • Point tenderness over right lower ribs
79
Q

What investigations are used to diagnose amoebic liver abscesses?

A
  • Abnormal LFTs
  • CXR – raised right hemi-diaphragm
  • USS/CT scan
  • Serology
  • Stool microscopy - often negative
80
Q

How are amoebic liver abscesses treated?

A
  • Metronidazole or Tinidazole
  • If pyogenic abscess, Tx with empirical antibiotics
  • Clear the gut lumen of parasites (Paramomycin/ Diloxanide)
81
Q

What causes giardiasis and how is it spread?

A
  • flagellated protozoa
  • Invades duodenum and proximal jejunum
  • Faecal-oral spread (contaminated water)
  • Incubation ~ 7 days
82
Q

How does giardiasis present?

A
  • Watery, malodorous diarrhoea
  • Bloating, flatulence
  • Abdominal cramps
  • Weight loss
83
Q

How is giardiasis investigated?

A
  • Stool microscopy for cysts
  • PCR tests (in developed countries)
  • OGD for duodenal biopsy (rarely necessary)
84
Q

How is giardiasis treated?

A
  • Metronidazole

- Tinidazole

85
Q

Helminth infections are caused by what?

A

Parasites!

86
Q

Helminth infections are associated with an increase in which type of white blood cell?

A

Eosinophilia

87
Q

What are the different types of Helminth infections?

A

Nematodes (Roundworms)
=> Intestinal roundworms
=> Tissue roundworms (filariasis)

Trematodes (Flukes)

Cestodes (Tapeworms)
=> Intestinal or Larval

88
Q

Give an example of a Trematode (Fluke) infection?

A

Schistosomiasis – from fresh water exposure

89
Q

What sources of Tapeworm can give rise to infection?

A
  • Eating undercooked meat containing infectious larval cysts
  • Either PORK or BEEF
90
Q

What is Chagas disease caused by and how is it transmitted?

A

Trypanosmiasis

- Transmitted by the kissing bug (Triatome)

91
Q

How does Chagas disease affect the body?

A
  • Causes parasymphathetic denervation affecting the colon and/or oesophagus
  • May cause Megaoesophagus

GI (33 decks)

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