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17 Cards in this Set

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What are the usual defense mechanisms of the GI tract?
-Stomach has HCl
-Intestines: normal flora, peristalsis, sIgA, Phagocytes.
What are the 3 types of pathogenic mechanisms in the GI tract?
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?
1. Abdominal pain
2. Diarrhea
3. Dysentery
4. Botulism (neurological symptoms)
When and how should stool specimens be collected?
-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.
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?
-Brilliant green agar
-Bismuth sulfite agar
Other than enteric plates, what should be inoculated from a stool specimen?
-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?
-Tetrathionate
-Selenite
-GN broth
On a daily timeframe, how do you do an enteric workup?
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?
-Enterobacteriaceae
-Streptococci (enterococci)
-Anaerobes
-Pseudomonas
-Staphylococci
-Yeast
What enteric pathogens would you culture FOOD (not stool) for?
-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.