Indole test: Difference between revisions
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+ | *Tests for the presence of tryptophanase, which metabolizes tryptophan to indole |
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+ | *May be done either as a '''conventional tube indole''' (overnight incubation) or as a '''spot indole''' rapid test |
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+ | **The tube test requires overnight incubation at 37°C in ambient air, then add the reagent; it turns pink if positive |
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+ | **The spot test is quick, testing for indole reacting with cinnamaldehyde to give a '''blue-green''' colour within 30 seconds |
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+ | *Helps to differentiate species within the ''Enterobacteriaciae'' |
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+ | **Most strains of [[Escherichia coli]], [[Proteus vulgaris]], [[Morganella morganii]] and [[Providencia]] are indole-positive |
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+ | **Specifically can help identify species within a genus: |
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+ | ***[[Klebsiella]]: [[Klebsiella oxytoca]] is indole-positive whereas [[Klebsiella pneumoniae]] and [[Klebsiella aerogenes]] are indole-negative |
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+ | ***[[Citrobacter]]: [[Citrobacter koseri]] is indole-positive where as [[Citrobacter freundii]] is indole-negative |
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+ | ***[[Proteus]]: [[Proteus vulgaris]] is indole-positive whereas [[Proteus mirabilis]] is indole-negative |
+ | **Notable indole-negative species include [[Salmonella]], [[Hafnia]], [[Enterobacter]] |
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+ | **[[Yersinia enterocolitica]] and some [[Shigella]] are indole-variable |
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[[Category:Diagnostics]] |
[[Category:Diagnostics]] |
Latest revision as of 22:55, 7 February 2022
- Tests for the presence of tryptophanase, which metabolizes tryptophan to indole
- May be done either as a conventional tube indole (overnight incubation) or as a spot indole rapid test
- The tube test requires overnight incubation at 37°C in ambient air, then add the reagent; it turns pink if positive
- The spot test is quick, testing for indole reacting with cinnamaldehyde to give a blue-green colour within 30 seconds
- Helps to differentiate species within the Enterobacteriaciae
- Most strains of Escherichia coli, Proteus vulgaris, Morganella morganii and Providencia are indole-positive
- Specifically can help identify species within a genus:
- Klebsiella: Klebsiella oxytoca is indole-positive whereas Klebsiella pneumoniae and Klebsiella aerogenes are indole-negative
- Citrobacter: Citrobacter koseri is indole-positive where as Citrobacter freundii is indole-negative
- Proteus: Proteus vulgaris is indole-positive whereas Proteus mirabilis is indole-negative
- Notable indole-negative species include Salmonella, Hafnia, Enterobacter
- Yersinia enterocolitica and some Shigella are indole-variable