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Microbiology > Microbiology - GI Infections > Flashcards

Microbiology - GI Infections Flashcards

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1
Q

What are the major defences of the GI tract? (4)

A

Acid
Mucus
Normal Flora
Intestinal Motility

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2
Q

What are the substances which destroy the major defences? Acid destruction? Normal flora destruction? Intestinal motility destruction?

A

Acid: Proton pump inhibitor
Normal flora: Antibiotics
Intestinal motility: Opiates

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3
Q

What is the only organism that targets the stomach?

A

Helicobacter pylori

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4
Q

What allows H. pylori to survive in the stomach? (3 virulence factors)

A

Its motility allows it to live in the gastric mucus and adhesins allow attachment to mucosal lining. Urease breaks down urea and forms ammonia (used to neutralize acid).

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5
Q

What diseases are caused by H. pylori infection? (3)

A

Peptic ulcer disease
Gastric adenocarcinoma
Gastric lymphoma

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6
Q

What types of ulcers are found in peptic ulcer disease?

A

Gastric and duodenal ulcer.

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7
Q

How does peptic ulcer disease present? (2)

A

Epigastric pain after eating

Gnawing/burning sensation

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8
Q

What is the cause of peptic ulcer disease? (1 bacteria, 1 other reason)

A
  1. H. pylori infection

2. NSAIDs (even low dose aspirin use in elderly)

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9
Q

How do you diagnose peptic ulcer disease? (3)

A
  1. Urea breath test (urease breaks down urea)
  2. ELISA - Stool antigen test (find H. pylori)
  3. Gastric biopsy + urease test
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10
Q

How do you treat peptic ulcers? (2)

A
  1. Proton Pump Inhibitors

2. Antibiotics (2 or 3 of them)

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11
Q

What is the structure and physiology of H. pylori?

A

GN spiral, microaerophile

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12
Q

Where can you find H. pylori?

A

Stomach of 50% of the worlds population

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13
Q

How is H. pylori spread?

A

Oral-oral and oral-fecal route.

Or…if you drink it to prove a point that it causes peptic ulcers like an IDIOT!

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14
Q

What are the virulence factors of H. pylori? Functions? (3)

A
  1. Flagella - movement through mucous
  2. Adhesins - attachment to gastric epithelium
  3. Urease - neutralize gastric acids
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15
Q

How is diarrhea classified?

A

It is classified as having 3 or more loose stools per day (lasts <14 days)

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16
Q

What are the steps required in assessing a patient with diarrhea? (5)

A
  1. Is there blood/mucous/both in stool?
  2. Is there FEVER?
  3. Is there abdominal pain?
  4. What is the extent of dehydration?
  5. What is the patients history (i.e., diet)?
17
Q

What are the two different types of diarrheal presentations? (2) What part of the GI tract affected?

A
  1. Non-inflammatory (watery diarrhea) - small intestines

2. Inflammatory (dysentery) - large intestines

18
Q

What is the general problem in non-inflammatory diarrhea? Observations?

A

Alterations in absorption and/or secretion processes.

Observe: NO FECAL LEUKOCYTES

19
Q

What is the general problem in inflammatory diarrhea? Observations?

A

Cytotoxins or invasion of bacteria leads to inflammatory response in the intestine.

Observe: MUCOUS, BLOOD, FECAL LEUKOCYTES

20
Q

What is the general pathophysiology of non-inflammatory diarrhea?

A

Bacteria can enter the GI tract via contaminated water and bind to the mucosal lining of the intestine (DO NOT INVADE MUCOSA). Release of enterotoxin (most bacteria do this) which increase fluid loss to lumen of small intestine.

21
Q

What is a major concern for those with non-inflammatory diarrhea?

A

DEHYDRATION

22
Q

What is the TX for non-inflammatory diarrhea?

A

Supportive care and no antibiotics (self limiting cases), so just REHYDRATION

23
Q

What are the most common causes of watery diarrhea (from most common to least)(3)?

A
  1. Viruses
  2. Bacteria
  3. Other
24
Q

What are the 7 bacteria that cause non-inflammatory diarrhea? (7)

A
  1. S. aureus
  2. B. cereus
  3. C. perfringens
  4. E. coli (ETEC, EPEC, EAEC)
  5. V. cholera
  6. V. prahaemolyticus
  7. L. monocytogenes
25
Q

What type of drug increases the risk of non-inflammatory diarrhea?

A

Proton pump inhibitors

26
Q

What is the virulence factor responsible for S. aureus non-inflammatory diarrhea?

A

Enterotoxin present in food (pre-formed heat stable (superantigen) toxin) which acts on the SMALL intestine

27
Q

What are the SX associated with S. aureus non-inflammatory diarrhea?

A

Vomiting, diarrhea, abdominal pain

28
Q

What is the incubation period of S. aureus non-inflammatory diarrhea? How long does it last?

A

Incubation: 2-6 hours
Lasts: <24 hours

29
Q

What types of food cause S. aureus non-inflammatory diarrhea?

A

Processed meats and dairy products

30
Q

What are the two forms of B. cereus infection and cause?

A
  1. Emetic disease (reheated rice) with B cereus spores

2. Diarrheal disease (contaminated food)

31
Q

How does the emetic form of B. cereus cause its SX? Incubation period and duration?

A

Germinating spores produce heat stable toxin that cause vomiting, nausea and abdominal cramps.

Incubation: Onset w/in 6 hours
Duration: <24 hours

32
Q

How does the diarrheal form of B. cereus cause its SX? Incubation period and duration?

A

Spores contaminate the food, toxin formed in GI and acts on small intestine causing diarrhea and abdominal cramps.

Incubation: 8-12 hours
Duration: <24 hours

33
Q

What foods cause B. cereus infection (diarrheal form)?

A

Meats, vegetables and sauces (gravies)

34
Q

Treatment for both the emetic and diarrheal forms of B. cereus infection?

A

ORAL REHYDRATION

35
Q

How does C. perfringens cause diarrhea?

A

Diarrhea caused by enterotoxin (heat labile) produced in small intestine.

36
Q

What is the incubation period for C. perfringens causing diarrhea and the duration of the disease?

A

Incubation period: 8-24 hours

Lasts: <24 hours

37
Q

What food causes C. perfringens diarrhea?

A

Meat and meat products

38
Q

What is the treatment for C. perfringens diarrhea?

A

ORAL REHYDRATION

Microbiology (5 decks)

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