GI tract
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- What are the usual defense mechanisms of the GI tract?
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-Stomach has HCl
-Intestines: normal flora, peristalsis, sIgA, Phagocytes. - What are the 3 types of pathogenic mechanisms in the GI tract?
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1. Enterotoxins affect cell function (by either being ingested preformed or forming after ingestion)
2. Organism growth disrupts intestinal mucosa function
3. Organism growth damages intestinal mucosa - What are 4 symptoms associated with GI infection?
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1. Abdominal pain
2. Diarrhea
3. Dysentery
4. Botulism (neurological symptoms) - When and how should stool specimens be collected?
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-During the most acute phase of the disease.
-Collect 2-3 specimens if possible.
-Don't settle for swabs - try to get fecal specimen if poss. - How should you hold a fecal specimen if unable to culture right away?
- Put in the refrigerator to prevent overgrowth of normal flora.
- When processing a stool culture, is a direct smear normally done?
- No - not unless it's requested.
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If a fecal smear is requested what would you be looking for?
What type of stain is used? - Fecal leukocytes with Methylene blue.
- What does the presence of WBCs in a fecal specimen indicate?
- Presence of a pathogen - Salmonella, shigella, campy, C. difficile, or Cryptosporidium.
- You know the low/intermed selective enteric plates; what are the 2 high selective plates?
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-Brilliant green agar
-Bismuth sulfite agar - Other than enteric plates, what should be inoculated from a stool specimen?
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-CNA
-BA
-Campy, CIN, SMAC, or TCBS. - What is the purpose of enrichment media?
- Keeps the normal flora from growing and promotes the growth of fastidious pathogens.
- What are the 3 normal types of enrichment broths?
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-Tetrathionate
-Selenite
-GN broth - On a daily timeframe, how do you do an enteric workup?
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Day 1: possibly fecal leukocyte direct smear, inoculate primary.
Day 2: Screen for pathogens - inoculate nonferm. to TSI/LIA; subculture the enrichment broth. - What are 6 normal flora seen in the enteric specimen?
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-Enterobacteriaceae
-Streptococci (enterococci)
-Anaerobes
-Pseudomonas
-Staphylococci
-Yeast - What enteric pathogens would you culture FOOD (not stool) for?
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-Bacillus cereus
-Clostridium perfringens
-Listeria - How would you test for Clostridium difficile?
- Toxin assay on stool
- How would you test for Clostridium botulinum?
- Toxin assay on serum.