Indole test: Difference between revisions

Revision as of 10:06, 14 August 2020

Tests for the presence of trypophanase, 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 positive
- Specifically can help identify species within a genus:
  - Klebsiella species: 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
  - Proteus species: Proteus vulgaris is indole positive whereas Proteus mirabilis is indole negative
- Notable indole-negative species include Salmonella species, Hafnia species, Enterobacter species
- Yersinia enterocolitica and some Shigella species are indole-variable

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-* Tests for the presence of trypophanase, which metabolizes tryptophan to indole
+*Tests for the presence of trypophanase, 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 col]]''i,'' [[Proteus vulgaris]], [[Morganella morganii]] and [[Providencia species|Providencia]] are 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 species|''Klebsiella'' species]]: ''[[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 species|''Citrobacter'' species]]: ''[[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 species|''Proteus'' species]]: ''[[Proteus vulgaris]]'' is indole positive whereas ''[[Proteus mirabilis]]'' is indole negative
+**Notable indole-negative species include [[Salmonella species]], [[Hafnia species]], [[Enterobacter species]]
+**[[Yersinia enterocolitica]] and some [[Shigella species]] are indole-variable
 [[Category:Diagnostics]]