Miscellaneous Bench (stools) Flashcards
What are the enteric pathogens that would be cultured on a routine stool work-up?
Salmonella
Shigella
Campylobacter
Escherichia coli 0157:H7
What enteric pathogens can be cultured but require special request by the physician?
Yersinia Aeromonas Plesiomonas Vibrio Listeria Clostridium difficile
How should stool specimen be maintained (and how long) if they cannot be immediately processed?
room temp/ unpreserved -
What is the recommended transport medium as an alternative to fresh specimens?
- for routine specimen?
- for Vibrio?
Modified Carey-Blair
- buffered glycerol saline for salmonella and Shigella
- buffered glycerol saline enriched with CACl2 for Vibrio and Campylobacter
List 5 reasons for unacceptable stool specimens
- contaminated with urine and/or water
- contaminated with castor oil, bismuth, or barium
- Multiple spemimens submitted on the same day
- dry rectal swabs and stools sent in diapers or paper cups
- unpreserved stool specimens greater than one hour old
Media used to culture routine stool pathogens (and temperatures)
- BAP (35C ambient air for 24 hours)
- Enteric agar media=MAC/HEK/MAC SORBITOL (35C in ambient air for 24 hours)
- Campylobacter media (microaerophilic, capnophilic, 42C for 48 hours)
What are capnophilic conditions?
5% O2
10% CO2
85% N2
Media used and proper incubation for:
- Aeromonas species
BAP plate employing the cytochrome oxidase test. CIN or YSA may be used as a selective medium.
Media used and proper incubation for:
- Plesiomonas shigelloides
BAP plate employing the cytochrome oxidase test
Media used and proper incubation for:
- Vibrio species
Selective agar: TCBS incubated at 35C ambient air for 48 hours
Media used and proper incubation for:
- Yersinia species
YSA plate after 48 hours incubation at 25C
MAC plate after 48 hours incubation at 25C
Potenital pathogen colonial morphology on a BAP
Screen for Aeromonas and Plesiomonas by testing for cytochrome oxidase positive colonies
Potenital pathogen colonial morphology on a MAC
Clear or transparent colony
Potenital pathogen colonial morphology on a HEK
Green or black colony
Potenital pathogen colonial morphology on a MAC SORB
Clear or transparent colony
Potenital pathogen colonial morphology on a YSA
Any colony
Potenital pathogen colonial morphology on a Charcoal CAMPY
Non-hemolytic grey or colorless colonies can be flat with irregular edges or round and convex with entire edges. Colonies can be pin point or spreading along streak lines, some spread all over plate
Potenital pathogen colonial morphology on a TCBS
Yellow or green colony
Potenital pathogen colonial morphology on a PALCAM
Blackening around colony
How can a rapid urease help to rule out stool pathogens?
all positive urease isolates can be dismissed as normal flora
Campylobacter jejuni:
- typical gram stain
small, curved gram negative rods
Campylobacter jejuni:
- catalase? oxidase? hippurate test result?
Cat: pos
Ox: pos
Hip: pos
Report to the State Board of Health
Salmonella
E. coli 0157:H7
Shigella?
Campylobacter?
Shiga Toxin Producing E. coli methods:
- which methods screens for only O157
EHEC by EIA testing
Shiga Toxin Producing E. coli methods:
- purpose of broth
*
Shiga Toxin Producing E. coli methods:
-
Examine on MAC SORBITOL for colorless or clear colonies. Test with 0157:H7 Latex Kit
How do you identify
- Salmonella
*
How do you identify
- Shigella
*
How do you identify
- E. coli 0517
*
Organisms that cause food poisoning “infections”
*
Organisms that cause food poisoning “intoxications:
*
Why are cultures of stool not effective for diagnosing intoxications?
*
Differences between the O, H, and K antigens found on the Enterobacteriaceae stool pathogens
*
O antigens associated with stool pathogens
*
H antigens associated with stool pathogens
*
K antigens associated with stool pathogens
*
Significance of H. pylori with respect to disease
peptic ulcers
How is H. pylori infection diagnosed?
*
