Indole test: Difference between revisions

Latest revision as of 02:55, 8 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

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-* Tests for the presence of trypophanase, which metabolizes tryptophan to indole
+*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
+*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 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
+**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''
+*Helps to differentiate species within the ''Enterobacteriaciae''
-** Most strains of ''E.coli,'' ''P. vulgaris'', ''M. morganii'' and ''Providenica''
+**Most strains of [[Escherichia coli]], [[Proteus vulgaris]], [[Morganella morganii]] and [[Providencia]] are indole-positive
-** Specifically can help identify species within a genus:
+**Specifically can help identify species within a genus:
-*** ''Klebsiella'' species: ''Klebs‪iella oxytoca'' is indole positive whereas ''Klebsiella pneumoniae'' is indole negative.
+***[[Klebsiella]]: [[Klebs‪iella oxytoca]] is indole-positive whereas [[Klebsiella pneumoniae]] and [[Klebsiella aerogenes]] are indole-negative
-*** ''Citrobacter'' species: ''Citrobacter koseri'' is indole positive where as ''Citrobacter freundii'' is indole negative
+***[[Citrobacter]]: [[Citrobacter koseri]] is indole-positive where as [[Citrobacter freundii]] is indole-negative
-*** ''Proteus'' species: ''Proteus Vulgaris'' is indole positive whereas ''Proteus mirabilis'' 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
 [[Category:Diagnostics]]