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Phase 2: Gastrointestinal System > Lecture 15: Enteric Infection > Flashcards

Lecture 15: Enteric Infection Flashcards

1
Q

What are the 3 most common symptoms of enteric infection?

A
  • Vomiting
  • Diarrhoea
  • Non-intestinal manifestations e.g. paralysis of the face
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2
Q

What is an enteric infection?

A

The name given to any disease caused by an intestinal infection

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3
Q

How common is vomiting?

A

Very rare- nausea (the feeling of sickness) is more common

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4
Q

When vomiting is the predominant symptom what certain aetiologies does the suggest?

A
  • Staphylococcus aureus
  • Bacillus cereus
  • Norovirus
  • Food poisoning
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5
Q

Nausea is a common symptom of ___ gastroenteritis

A

Infectious gastroenteritis

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6
Q

Define gastroenteritis?

A

Gastro- means stomach

enteron- means small intestine

inflammation of the stomach and small intestine, typically resulting from bacterial toxins or viral infection.

Gastroenteritis is defined as a diarrheal disease

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7
Q

Describe the mechanism utilised by the toxins in order to survive so they can be ingested in food?

A

Common in food that is kept warm on hot plates or reheated food.

The bacteria grow on the food and release these toxins into the food. When heated, the bacteria die but many of these toxins a heat-resistant and therefore are still present on the food.

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8
Q

Define diarrhoea?

A

Diarhhoea is defined as 3 or more loose or watery stools in 24 hours or at least 200 grams of stool per day

The stool must hold the shape of its container i.e. liquid consistency

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9
Q

What are the major differences between small and large bowel associated diarrhoea?

A

Small intestine:

Cause is usually fluid and enzyme secretion

Signs are large volume of watery diarrhoea

Rare blood or fever

Cramps and bloating due to the distention of the SI

large intestine:

Cause is absorption of fluid and salt

Frequent defecation but small volume (painful stool)

Fever and blood is common

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10
Q

Give examples of pathogens that produce toxins prior to consumption?

A

Staphylococcus aureus

Bacillus cereus

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11
Q

Give examples of pathogens that produce toxins after consumption?

A

Clostridium difficle

Escherichia coli (E.coli) 0157 (important to remember the name as E.coli have many strains some good some bad)

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12
Q

What are the 3 major pathogenic mechanisms for gastroenteritis?

A
  • Toxin mediated
    • Organisms produce toxins (before prior or after consumption)
  • Damage to the intestinal epithelial surface
  • Invasion across the intestinal epithelial barrier
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13
Q

Give examples of bacteria that can cause gastroenteritis?

aka bacterial gastroenteritis

A

Campylobacter (most common)

Salmonella

Shigella

E.coli 0157

Clostridium difficle

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14
Q

Give examples of viruses that can cause gastroenteritis?

aka viral gastroenteritis

A

Norovirus

Sapovirus

Rotavirus

Adenoviruses

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15
Q

Sapovirus, rotavirus and adenoviruses are common viral infections in which group of patients?

A

Common cause of illness in children

Less so in adults

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16
Q

Norovirus is a common viral infection in which group of patients?

A

Adults

Less common in children (while sapovirus, rotavirus and adrenoviruses are common in children)

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17
Q

Give examples of parasites that can cause gastroenteritis?

aka parasitic gastroenteritis

A

Cryptosporidium

Giardia (found in contaminaed food and water- important take a travel history)

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18
Q

Why is Cryptosporidium infections common in the UK?

A

Because the cryptosporidium parasite infects both humans and farm animals

More common in spring months (in the lambing season) because if the lamb is infected with this parasite then so will their feces. The parasite gets washed away from the feces and enters surrounding water supply.

Common as well with patient attending farming and lamb petting events

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19
Q

What are the 3 goal stands when assessing a patient with enteric infection?

A
  • 1st is history
    • Most important
  • Stool examination/ culture
    • Difficult since the feces will have numerous organisms present (Due to the microflora of the gut)
    • Selective mediums to grow the culture in
  • Endoscopy
    • Looking for the signs of infection (Remember PRISH- pain, redness, immobility, swelling and heat)
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20
Q

Name some the key aspects when taking a history for a patient with suspected enteric infection? and why

A
  • Food history
    • Ingestion of any toxins
  • Occupation
    • Certain jobs put people at higher risk e.g. live stock workers.
  • Travel
  • Pets
    • Snakes are covered in multiple organisms
  • Recent antibiotic use
    • Useful to identify Clostridium difficle
  • Co-morbidity
    • Infection can destabilise chronic illnesses
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21
Q

Describe the pros and cons of stool culture in gastroenteritis?

A

Cons:

Majority of the time it is not used as by the time the organism is cultured the diarrhoea is gone (usually lasts 48 hours).

Low rate positive stool culture: hard to recreate the bowel environment- therefore many organisms cannot be cultured.

Pros:

Useful to indicate possible treatments and to document the pathogen

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22
Q

What is a more useful technique instead of stool culture for parasites only?

A

Look at the stool down a microscope.

Can identify eggs if parasite is present

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23
Q

Describe the pros and cons of endoscopy for gastroenteritis?

A

Rarely used for gastroenteritis

Useful to rule out non-infectious causes e.g. IBD.

Occasionally useful when the diagnosis requires biopsy.

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24
Q

What is the goal stand treatment for gastroenteritis?

A

Oral rehydration solution to prevent dehydration

Self-limiting: will get better on its own

May require IV fluid replacement if they cannot keep fluids down (i.e. more fluids out than in)

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25
Give an example of an enteric infectious agent that if antibiotics are given it will make the infection **worse** than better?
E.coli 0157 If you give antibiotics with 0157, the E.coli responds by producing more toxins Treatment is IV fluid and monitor kidney function
26
On average, antibiotics use reduces the duration of diarrhoea from __ to \_\_?
Without antibiotics diarrhoea would last aprrox. 2.8 days With antibiotics around 1.7 days Reduction by ONE DAY
27
What are the 3 groups of people that antibiotics may help if they have diarrhoea?
* Very ill patients * Immunocompromised etc * Significant comorbidity * Certain causes * Clostridium difficle infection
28
Why are loperamide or other OTC medication not advised with patients with diarrhoea? When is it appropriate
Diarrhoea is the body's mechanism to remove toxic pathogens. Therefore by reducing the diarrhoea, the body is unable to remove the toxins. Therefore, it increases the length of infection (As it takes the body longer to remove the toxins) and increases the risk of invasion from invasive organisms (as they are staying longer in the intestines)
29
What is a unique recommendation with patients suffering with Giardia infection?
Recommended to exclude lactose for a period of time
30
Define the term "infecting dose"?
Infectious dose is the smallest quantity of infectious material that regularly produces infection A bacteria with a high infectious dose requires lots of the bacteria in order to produce an infection in the host
31
Is the infectious dose for Campylobacter high or low?
High infectious dose
32
Why are people taking PPI or other drugs to reduce stomach acid at a higher risk to Campylobacter?
Campylobacter are sensitive to the stomach acid, therefore one of the mechanisms to prevent infection. People taking PPI are at higher risk as they have a reduction in this preventative mechanism
33
Name the clinical features for Campylobacter infection?
* Fever * Diarrhoea * Frequent and can be high volume * Blood in stool common * Abdominal pain * Nausea is common * Vomiting is rare
34
What is the standard treatment for Campylobacteri?
Self-limiting Lasts approx 7 days Will get better on its own
35
When taking a history about an infection, why must you ask if they keep or have recently been in contact with reptiles ?
Reptiles, e.g. snake, have a high level of Salmonella on their skin
36
Describe the public health measure that has resulted in a large decline in the number of cases of Salmonella?
Factory chickens are being vaccinated against Salmonella, one of the major ways in which Salmonella was transferred to humans
37
What is the infection dose for Salmonella?
Very high approx. 10,000 organisms
38
If you take a higher innoculum of the organisms what happens to the time of onset?
More rapid onset
39
Salmonella infection you get clinical symptoms after how long?
—Illness within 72 hrs ingestion
40
Which infection is significant in food handlers and why?
Salmonella infection The median duration of salmonella shedding after intestinal infection is 5 weeks. During this time, hosts are asymptomatic
41
Define bacteria shedding?
Humans shed bacteria throughout the course of the infection. Shedding can last for several days to several weeks, and people may become temporary carriers for several months or longer.
42
What is Verocytotoxigenic Escherichia coli (VTEC)?
VTEC is a particular group of the bacterium Escherichia coli. Although most strains of E. coli are harmless and live in the intestines of healthy humans and animals, VTEC strains produce a powerful toxin and can cause severe illness. Most common member is E.coli 0157
43
Most common ways in which people get VTEC?
* Direct contact with VTEC-contaminated faecal material, as a result of handling or petting animals e.g. petting zoos. * Fruit and vegetables can be contaminated if they come in contact with soil, animal faeces or manure which contains VTEC.
44
What is the infectious dose for E.coli 0157?
Small infectious dose As little as 10 organisms i.e. highly infectious
45
Describe the clinical features of E.coli 0157?
* Incubation period 3 to 4 days * Bloody diarrhoea & abdominal tenderness * Fever is rare
46
Discuss Clinical features of gastroenteritis
* Watery, usually nonbloody diarrhea — bloody diarrhea usually means you have a different, more severe infection. * Abdominal cramps and pain. * Nausea, vomiting or both. * Occasional muscle aches or headache. * Low-grade fever.
47
Discuss the management of infectious diarrhoea
Self-limiting will get better on its own. Dehydration required due to the high level of fluid loss In high risk groups, e.g. children and elderly, antibiotics may be useful but very rare
48
Describe the pathogenesis of E.coli 0157 infection?
E.coli attach to the gut mucosa. Starts to produce Shiga toxin The Shiga toxin induces apotosis of the enterocytes The Shiga toxin enters the systemic circulation and transferred into endothleial cells causing damage to blood vessels in certain organs including the kidney. Results in bloody diarrhoea
49
Describe the pathogenesis of Salmonella?
Salmonella organisms are ingested in food survive passage through the gastric acid barrier and invade the mucosa of the small and large intestine and produce toxins. The salmonella organisms invade the epithelial cells stimulating the release of proinflammatory cytokines which induce an inflammatory reaction
50
Describe the pathogenesis of Campylobacter
Initiated by the ingestion of contaminated food or water The organisms penetrate the gastrointestinal mucus and adhere to the gut enterocytes. Once adhered can then induce diarrhoea by toxin release
51
What is the major risk factor for Clostidiodes Difficile infection?
Broad spectrum antibiotic use
52
Describe the pathogenesis of Clostidiodes Difficle infection?
Results from a disturbance of the normal bacterial flora of the colon - Reduced colonisation resistance The C difficle colonises the gut and releases toxins The toxins cause mucosal inflammation and damage
53
When taking a stool sample for enteric infections, what two things are you looking for and why?
Looking for the bacteria antigen and toxin. Bacteria antigen to make sure the bacteria is present. But positive results might be due to "non-toxic" stains of the bacteria (take make up the normal gut micobiota). Must look for the toxin also to clarify that the bacteria present is toxic to the gut
54
Describe the treatments options for Clostidiodes Difficle infection?
* Stop causative antibiotic use * Use narrow spectrum antibiotic (Metronidazole /Vancomycin) to destroy the C.diff * Allow the microbiota to recolonise. * Possibility of the flora to be recolonised by C.Diff. In recurrent C.Diff infection, fecal transplantation may be required
55
Metronidazole and vancomycin are used in the treatment of Clostridioides difficle infection. Why is the best mechanism of giving the drug and why?
**Metronidazole = Intravenous + Oral** **Vancomycin= Oral only** Vancomycin must be given orally because intravenous vancomycin does not concentrate in the bowel mucosa
56
What is the most common viral gastroenteritis cause?
Norovirus
57
Why is norovirus highly transmissible?
Gains entry into the body via the faecal oral route Low infectious dose approx 10-100. i.e. it does not require high numbers of organisms to cause the infection Very stable in the environment e.g. can survive in temperatues above 60.
58
One technique to reduce transmission of infection is to use soap and water instead of alcohol gel. Which infective organisms is this important in protecting against?
Norovirus because the norovirus organisms are highly stable
59
What is often the best indicator of aetiology for enteric infections?
History
60
What are the normal treatment options for enteric infections?
—Rehydration —Antibiotics rarely indicated (self limiting)

Phase 2: Gastrointestinal System (30 decks)

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