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HUMAN HEALTH AND DISEASE > Infections of the GI Tract > Flashcards

Infections of the GI Tract Flashcards

1
Q

What does the normal microbiome look like for the stomach, SI, & LI?

A

Stomach- sterile, contains only a few organisms because of low pH and enzymes

SI- streptococci, lactobacilli and yeasts, the proportions of which depend on dietary habits

LI- dense population of varied flora: Strep faecalis, Bacteroides spp, enterobacteriaceae, Clostridium spp, anaerobic streptococci

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2
Q

What is gastroenteritis, what is associated with it, and who commonly gets it?

A

Acute gastrointestinal illness usually due to infection.

You get vomiting and diarrhoea and it’s often associated with food poisoning.

Can occur at all ages, but infants principal group

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3
Q

Where is gastroenteritis more common?

A

More common in countries with poor hygiene standards, water sanitation problems.

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4
Q

What are some bacterial causes of gastroenteritis and their individual incubation periods?

A

look at the slides

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5
Q

What are some other non-bacterial causes of gastroenteritis and their incubation periods?

A

There are also viral and parasitic causes.

look at the slides

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6
Q

What are the main groups at risk of contracting gastroenteritis?

A

-Enteric hygiene difficulties
-Pre-school, creche children
-Food workers
-Health care staff

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7
Q

What is the commonest bacterial gastroenteritis in the Western world?

A

Gastroenteritis secondary to Campylobacter, with C. jejuni & C. coli being some of the most common diarrhoea-inducing agents in the Western world.

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8
Q

What are the characteristics of campylobacter?

A

Curved, slender, Gram negative bacilli

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9
Q

What are the signs and symptoms associated with campylobacter gastroenteritis?

A

-Incubation period which can be up to 4 days.

-these can be fever, myalgia, myalgia abdominal pain, and headaches.

-Diarrhoea occurs later & ranges from profuse, watery stools to bloody stools lasting up to one week.

-Patients may have prolonged carriage, however a chronic carrier state is rare

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10
Q

Can recurrent infection of campylobacter gastroenteritis occur?

A

Yes, in up to 25% of patients

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11
Q

Where can campylobacter be found?

A

In the gut or oral cavity

common sources are food (poultry; gut of bird), raw milk and dairy products

It can also infect young animals, like kittens or puppies, and then spread to humans

Caused by enterotoxins

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12
Q

How do you diagnose campylobacter gastroenteritis?

A

Via stool culture

Selective media, low Ox, 43C

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13
Q

Is treatment required for campylobacter gastroenteritis?

A

Not normally since it’s a self limiting infection

Erythromycin recommended for symptoms lasting more than 1 week

OR

If patient presents with worsening symptoms, dysentery, pyrexia, bacteraemia, is pregnant, or at risk of complications

(extremely young or elderly, immunocompromised, or those with liver cirrhosis)

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14
Q

Are there any post-infectious complications with campylobacter gastroenteritis?

A

Infection caused by salmonella bacteria.

This can cause a spectrum of diseases which can be divided into:

non-typhoidal types (causing self-limiting gastroenteritis)

typhoidal subtypes (like salmonella typhi, and salmonella paratyphi, which can cause typhoid fever)

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15
Q

What is the incubation period, symptoms & signs, and source of salmonellosis (non-typhoid)?

A

Incubation period : 1-2 days

Symptoms: Nausea, vomiting, diarrhoea, fever, abdominal pain and disseminated sepsis (severe sepsis)

Source: ingestion of contaminated food/water.

Also found in domestic animals and poultry e.g poultry, swine, cattle

Or from handling exotic pets

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16
Q

How long do the conditions caused by salmonella last and what are the possible outcomes?

A

Duration: 1-7 days

Gastroenteritis occurs in 75% of infections

Bacteraemia occurs in 5-10% of infections, often resulting in distant infections (e.g. CNS infections, endocarditis, or osteomyelitis)

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17
Q

Which groups are mostly affected by salmonella?

A

Infants, elderly and those with decreased stomach acid

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18
Q

How do you diagnose salmonella?

A

Stool culture

Enrichment and selective media

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19
Q

What is the treatment for salmonella infections?

A

Rehydration (treatment rarely necessary and antibiotic therapy is generally contraindicated as it would prolong the carriage of the organism in the convalescent phase and cause resistance)

Antibiotic therapy is only indicated for those with colitis, bacteraemia, haemoglobinopathies & immunocompromised states

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20
Q

Does salmonella have a high secondary spread?

A

Yes so it’s important to have strict contact precautions & clinical surveillance of contacts.

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21
Q

Describe the sources, and symptoms of Staphylococcus aureus.

A

Staphylococcus aureus - bacteria that can cause a range of infections of the skin, bone and heart valves.

When infected, it can cause nausea, vomiting and diarrhoea (25% of cases)

Usually due to cooked food not stored at 4 degrees/frozen immediately + food handler since organisms multiply in warm conditions

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22
Q

What is the incubation/duration period of staphylococcus aureus? What treatment is given?

A

Incubation: 1/2 - 6 hours.

Duration: 1-24 hrs (rarely 48)

Treatment: self-limiting, no treatment required

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23
Q

What is Bacillus cereus?

A

Aerobic spore-forming gram-positive bacillus which can contaminate foods such as rice, cereals, raw, dried & processed foods

It survives cooking/boiling by sporulation

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24
Q

What does the Bacillus cereus toxin cause?

A

Two types of poisoning: emetic (vomiting) and diarrhoeal (rare)

Symptoms (nausea & vomiting) usually occur within 2 to 6 hours after ingestion of contaminated food

Symptoms can last for 6 to 10 hours

No treatment required; self limiting

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25
Q

How can you prevent Bacillus cereus infection?

A

Adequate food hygiene & correct storage of food.

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26
Q

What is Shigellosis and what can it cause?

A

Most common species in developed countries producing mildest symptoms.

Due to contaminated food + water

Causes fever, malaise, self-limiting eatery diarrhoea (can have mucus, pus and blood)

Incubation: 48hrs

Locally invasive in large bowel

27
Q

Which species of Shigella is most likely to cause complications and how do you diagnose & treat this?

A

S. dysenteriae infection is most likely to cause complications such as HUS, dysentery, and toxic megacolon

Diagnosis- isolate organism on selective culture media

Treatment- rehydration

Antibiotics indicated for most patients- ciprofloxacin

28
Q

What is cryptosporidiosis?

A

A self limiting diarrhoeal illness in children that causes nausea & vomiting.

29
Q

How is cryptosporidiosis acquired?

A

By drinking contaminated water containing cysts of Crypto parvum found in infected cattle or humans and passed on in stools.

30
Q

Why is elimination of cryptosporidiosis difficult?

A

Because it’s very resistant to chlorination

A more severe illness results in those that are immunocompromised e.g. like in those that have AIDS

31
Q

How is cryptosporidiosis diagnosed?

A

By finding cysts in stool (acid ‘fast’)

There is no specific treatment

32
Q

What is Clostridium perfringens responsible for?

A

Gas gangrene and food poisoning

33
Q

How is Clostridium perfringens transmitted?

A

Heat resistant spores survive in contaminated foods during the heating procedure

After food is ingested- sporulation occurs in the GUT and an enterotoxin is produced

Also contamination of an open wound

34
Q

What are the symptoms, treatment, and prevention of Clostridium perfringens?

A

Symptoms- abdominal pain and watery diarrhoea

Treatment- symptomatic, no antibiotics

Prevention- good food hygiene, adequate cooking of food to kill the organisms

35
Q

What are the principal causes of infantile gastroenteritis?

A

Viral:
-rotavirus (the most common cause)
-noroviruses (Norwalk like)

Bacterial:
Escherichia coli

Different strains are classified based on their serological and virulence properties:

enteropathogenic; enterohaemorrhagic; enterotoxigenic; enteroinvasive

36
Q

What is the incubation period of viral gastroenteritis and what are the symptoms?

A

-Incubation period: 2-4 days

-Presents as acute diarrhoea of mild to moderate severity, may be vomiting

-Common in winter months

37
Q

How is viral gastroenteritis diagnosed & treated?

A

Diagnosed by detection of rotavirus antigen in stool.

Treatment is supportive care as medication not necessary.

38
Q

What can enteropathogenic E. coli cause (EPEC)?

A

More than 20 (O) serotypes have been identified in outbreaks of infantile diarrhoea.

39
Q

What can EPEC affect, how is it spread, and what are the symptoms, and how do you treat it?

A

Small intestine affected (local destruction of intestinal epithelial cells)

Spread by contaminated food

Symptoms include fever, nausea, vomiting, non-bloody stools

Self-limiting, supportive care, no specific antibiotic treatment

40
Q

What 2 types of diarrhoea can EPEC cause?

A

Infantile gastroenteritis (acute & profuse)

traveller’s diarrhoea (accompanied by abdominal pain & vomiting)

Both produce NON-BLOODY stools
Organism attaches to the small bowel and causes diarrhoea through enterotoxins

41
Q

What does enterohaemorrhagic E. coli (EHEC) produce?

A

Shiga toxin (STEC) or verotoxin (VTEC)

These ultimately cause colitis after an incubation period of 3-5 days

42
Q

What is the most common strain of EHEC & what does it cause?

A

O157:H7

Diarrhoea, bloody colitis, HUS (5%)

43
Q

How can EHEC infection occur and how should you treat it?

A

Ingestion of undercooked hamburger, salami, sprouts, and unpasteurised milk

Antibiotics and antimotility agents should be avoided if EHEC infection is suspected clinically

44
Q

What symptoms are associated with ETEC and how is it treated?

A

Ranges from mild to severe watery diarrhoea, cramps

Rehydration is main state of therapy

Antibiotics (quinolones, TMPSMX, and rifaximin) often are given empirically for moderate to severe traveller’s diarrhoea

45
Q

What symptoms does enteroinvasive E. coli (EIEC) cause and how does it affect the body?

A

Fever, watery diarrhoea, cramps

(Rarely) develops to (bacillary) dysentery, bloody stools

Large bowel affected, by invasion and local destruction of epithelial cells

46
Q

What is giardiasis?

A

SI infection caused by the flagellate protozoan Giardia lamblia.

47
Q

How is giardiasis acquired?

A

Ingestion of cysts in contaminated food or water (resists chlorination)

These develop into trophozoites in duodenum

Find cysts or rarely trophozoites in stool

48
Q

What symptoms do you get with giardiasis and when do they occur?

A

Symptoms present 1-2 weeks after ingestion and include cramping abdominal pain, flatulence, diarrhoea.

49
Q

What is the antimicrobial of choice in giardiasis?

A

Metronidazole

50
Q

What is Clostridium difficile (C. diff)?

A

Antibiotic associated pseudomembraneous colitis:

antibiotics (clindamycin, cephalosporins) suppress normal flora, C. diff multiplies, produces 2 toxins (cytotoxin and enterotoxin)

1st toxin binds to mucosal receptors causing cytotoxicity and inducing apoptosis.

2nd toxin enters the damaged mucosa causing further toxicity which leads to inflammation, haemorrhage etc

51
Q

How do you diagnose, treat & prevent C. diff?

A

Diagnosis- sigmoidoscopy, toxin in stool samples

Treatment- withdraw offending antibiotic, replace fluids, metronidazole, oral vancomycin

Prevention– wash hands/surfaces, selective use of antibiotics, isolate infected patients

52
Q

What is the causative organism of amoebic dysentery?

A

Entamoeba histolytica

53
Q

Where is ameobic dysentery common and how can it be acquired?

A

Indian sub Continent, Africa (but Worldwide distribution).

Acquired from eating food contaminated with cysts

54
Q

What are the symptoms associated with amoebic dysentery and how can it affect the body?

A

90% of individuals have no symptoms, but for the remaining 10%:

Can be severe diarrhoea with blood and mucus in stool

Can progress to cause perforation of large bowel and peritonitis

Also, you can have liver involvement with hepatitis or liver abscess

55
Q

What is the treatment for amoebic dysentery?

A

Metronidazole

56
Q

What is cholera caused by and how does it spread?

A

Caused by Vibrio cholerae and it’s typically water borne & infects only humans

It also has a short incubation period

57
Q

What is cholera and what can it cause?

A

A severe diarrhoeal illness with ‘rice water’ stools +/- vomiting and nausea

Can cause dehydration, electrolyte loss, circulatory and renal failure

58
Q

What is the mortality rate for cholera without treatment?

A

40%

59
Q

How do you diagnose and treat cholera?

A

Diagnosis with faecal culture

Treat by rehydration and antibiotics (tetracycline or ciprofloxacin)

60
Q

What may Helicobacter pylori infection give rise to?

A

Chronic gastritis and gastroduodenal ulceration, some cases of gastric carcinoma.

61
Q

What is H. pylori?

A

Gram negative bacterium

62
Q

How is H. pylori treated?

A

Treatment of H. pylori infection usually involves 7 days’ therapy with two antibiotics: (clarithromycin, metronidazole, and amoxicillin are often used)

together with a proton pump inhibitor (omeprazole)

Treatment fails in 10% of patients because of drug resistance

63
Q

How can we prevent foodborne illnesses?

A

Recognition of possible sources

Thorough cooking of food

Segregation of foodstuffs

Rapid cooling and good refrigeration

Store food so as to prevent multiplication

Treatment of foods likely to be contaminated

Exclusion of infections and other pests/vermin

Handwashing and hygienic practises

HUMAN HEALTH AND DISEASE (58 decks)

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