Microbiology - GI Infections Flashcards
What are the major defences of the GI tract? (4)
Acid
Mucus
Normal Flora
Intestinal Motility
What are the substances which destroy the major defences? Acid destruction? Normal flora destruction? Intestinal motility destruction?
Acid: Proton pump inhibitor
Normal flora: Antibiotics
Intestinal motility: Opiates
What is the only organism that targets the stomach?
Helicobacter pylori
What allows H. pylori to survive in the stomach? (3 virulence factors)
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).
What diseases are caused by H. pylori infection? (3)
Peptic ulcer disease
Gastric adenocarcinoma
Gastric lymphoma
What types of ulcers are found in peptic ulcer disease?
Gastric and duodenal ulcer.
How does peptic ulcer disease present? (2)
Epigastric pain after eating
Gnawing/burning sensation
What is the cause of peptic ulcer disease? (1 bacteria, 1 other reason)
- H. pylori infection
2. NSAIDs (even low dose aspirin use in elderly)
How do you diagnose peptic ulcer disease? (3)
- Urea breath test (urease breaks down urea)
- ELISA - Stool antigen test (find H. pylori)
- Gastric biopsy + urease test
How do you treat peptic ulcers? (2)
- Proton Pump Inhibitors
2. Antibiotics (2 or 3 of them)
What is the structure and physiology of H. pylori?
GN spiral, microaerophile
Where can you find H. pylori?
Stomach of 50% of the worlds population
How is H. pylori spread?
Oral-oral and oral-fecal route.
Or…if you drink it to prove a point that it causes peptic ulcers like an IDIOT!
What are the virulence factors of H. pylori? Functions? (3)
- Flagella - movement through mucous
- Adhesins - attachment to gastric epithelium
- Urease - neutralize gastric acids
How is diarrhea classified?
It is classified as having 3 or more loose stools per day (lasts <14 days)
What are the steps required in assessing a patient with diarrhea? (5)
- Is there blood/mucous/both in stool?
- Is there FEVER?
- Is there abdominal pain?
- What is the extent of dehydration?
- What is the patients history (i.e., diet)?
What are the two different types of diarrheal presentations? (2) What part of the GI tract affected?
- Non-inflammatory (watery diarrhea) - small intestines
2. Inflammatory (dysentery) - large intestines
What is the general problem in non-inflammatory diarrhea? Observations?
Alterations in absorption and/or secretion processes.
Observe: NO FECAL LEUKOCYTES
What is the general problem in inflammatory diarrhea? Observations?
Cytotoxins or invasion of bacteria leads to inflammatory response in the intestine.
Observe: MUCOUS, BLOOD, FECAL LEUKOCYTES
What is the general pathophysiology of non-inflammatory diarrhea?
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.
What is a major concern for those with non-inflammatory diarrhea?
DEHYDRATION
What is the TX for non-inflammatory diarrhea?
Supportive care and no antibiotics (self limiting cases), so just REHYDRATION
What are the most common causes of watery diarrhea (from most common to least)(3)?
- Viruses
- Bacteria
- Other
What are the 7 bacteria that cause non-inflammatory diarrhea? (7)
- S. aureus
- B. cereus
- C. perfringens
- E. coli (ETEC, EPEC, EAEC)
- V. cholera
- V. prahaemolyticus
- L. monocytogenes
