IMViC reactions
test is 4 in 1 biochemical related tests
breakdown/end product of tryptophan
indole
Sugar used as the basis for the methyl red test
glucose
name two media that can be used to detect citrate utilization
Koser's citrate broth and Simmon's citrate agar
medium used to test for indole production
Tryptone broth
medium used to test for methyl red and Voges-Proskauer
MR-VP broth
medium used to test for citrate in this lab
Simmon's Citrate agar
Chemical reagent used in indole test
Kovac's indole reagent; let stand 10 minutes
positive methyl red test pH
pH below 4.4
name two major end products produced by Voges-Proskauer positive organisms
2, 3 butanediol and acetonin
reagents used in the Voges-Proskauer test
Barritt's solution A and B
members of the Enterobacteriaceae or the enteric bacilli for which the IMViC tests are most useful belong to
coliform group
Enterics that do not fall into the two distinctive categories formed by E. coli and E. aerogenes are collectively referred to as
intermediates
Methyl red test
tests for fermentation of glucose by looking for acid production
when must indole production test be read
after 24 hour incubation, but no longer!
positive indole test
alcohol in Kovac's reagent separates out and turns red
negative indole test
alcohol in Kovac's reagent remains and color is unchanged
Media used in Methyl red test and Voges-Proskauer test
contains peptone, glucose and a phosphate buffer
Methyl red: if glucose has been fermented to acid
methyl red will be red, below pH of 4.4
Methyl red: if glucose has not been fermented
methyl red will be yellow, above pH of 4.4
Voges-Proskauer test
reaction results in red color complex formed by oxidation of 2, 3 butanediol and acetonin and presence of creatine and alpha-napthol
Voges-Proskauer: detection of glucose
red color complex forms if creatine and alpha-napthol are produced; may take 2 hours to develope
Citrate utilization
tests whether an organism can use 6-carbon citrate as its sole source of carbon
what must a cell need to carry citrate into cell
transport protein
Citrate test agar
Simmon's Citrate agar (green colored agar)
detection of citrate use
growth is observed on a slant and is accompanied by a change of the bromothymol blue indicator from green to deep blue
positive for citrate use
color of medium becomes bright blue
negative for citrate use
color stays the same green color
why are IMViC tests useful in differentiation?
differentiates subset of Gram negative, enteric bacteria known as the coliforms; helpful in spotting fecal contamination
Indole test
most E. coli strains produce indole
Enterobacter-Klebsiella group does NOT
Methyl red test
most E. coli strains are mixed acid fermenters
Enterobacter-Klebsiella group converts fermented glucose into neutral products
Voges-Proskauer test
most E. coli strains produce a negative result (no end products)
Enterobacter-Klebsiella group produce a positive result (end products)
Citrate test
E. coli strains cannot use citrate as a carbon source
Enterobacter-Klebsiella group can use citrate as a carbon source