Vibrio media Flashcards
What does “TCBS agar” stand for?
thiosulfate-citrate-bile salts-sucrose agar
What ingredients in TCBS agar inhibit gram positives?
ox gall, sodium cholate (bile salts)
What ingredients in TCBS agar inhibit Enterobacteriaceae?
sodium thiosulfate and sodium citrate
What is the pH of TCBS media?
8.6 (very alkaline)
What is the purpose of thymol blue and bromothymol blue in TCBS agar?
pH indicators (change color when sucrose fermentation occurs)
What color and colony morphology does Vc have on TCBS?
large, yellow colonies
What color does Vp have on TCBS?
blue/green colonies (indicates suc-)
What color and colony morphology does Va have on TCBS?
large, mucoidal, yellow colonies
Vh and Vf should have what color and characteristic on TCBS agar?
blue/green colonies that fluoresce
What types of organisms are inhibited on most selective and differntial Vibrio media? (2)
Gram pos
Enterobacteriaceae
What are two examples of organisms that may grow on TCBS?
Proteus/enterococci- small yellow colonies
Pseudomonas/aeromonas- small blue colonies
Growth should be partially inhibited!
What component of TCBSS agar is diffferent between brands and can cause problems with quality/reproducibility?
bile salts
What is the most common culture media for Vibrios?
marine agar/broth
not selective-get lots of background organisms in environmental samples
What are some problems with culture methods?
Almost none are specific for a single species and even fewer are selective for pathogenic organisms
What species of Vibrio was CHROMagar first developed for?
Vp (Hara-Kudo et al. 2001)
What is the recipe for CHROMagar
proprietary
has salts + a “chromogenic mix”
What is the pH for CHROMagar
9.0 (very alkaline)
What color is Vp on CHROMagar?
purple/violet
What color is Vv on CHROMagar?
pale blue
What color is Vc on CHROMagar?
pale blue
What color is Va on CHROMagar?
white/clear
What are some advertised benefits of using CHROMagar instead of TCBS?
fewer false positives, more Vibrio recovered
What color do suc+ Vibrios appear on TCBS?
yellow
What are two problems associated with growing Vv on TCBS?
Vv has very similar result to Vp– difficult to differentiate
TCBS media is thought to somewhat inhibitory for Vv
What is one problem associated with differentiating Vv on CHROMagar?
Vv and Vc have similar result (blue colonies)
Can sometimes get around by adding more salt
What media is recommended for the enrichment of Vibrio?
Alkaline peptone water
What is the concentration of Peptone in APW?
1-2% (2% more appropriate for marine species)
What is the pH of APW?
9.0
How does the MPN method work?
10X dilution of samples (usually triplicates), innoculate in nutrient broth to look for growth, use a table to determine MPN based on your results
Must confirm species using colony hybridization or other molecular test
What are the biochemical characteristics of Vp O3:K6 (pandemic strain associated with seafood-related illnesses in Asia and the US)
trh-
tdh+
urease-
How does colony hybridization work?
Grow colonies on solid media
Blot colonies onto a membrane
Preform cell lysis on membrane
Incubate with probes
Visualize using UV or autoradiography
