Indole test: Difference between revisions

Revision as of 10:09, 14 August 2020

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 species are indole-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 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 col]]''i,'' [[Proteus vulgaris]], [[Morganella morganii]] and [[Providencia species|Providencia]] are positive
+**Most strains of [[Escherichia coli]], [[Proteus vulgaris]], [[Morganella morganii]] and [[Providencia species]] are indole-positive
 **Specifically can help identify species within a genus:
-***[[Klebsiella species|''Klebsiella'' species]]: ''[[Klebs‪iella oxytoca]]'' is indole positive whereas ''[[Klebsiella pneumoniae]]'' and [[Klebsiella aerogenes]] are indole negative
+***[[Klebsiella species]]: [[Klebs‪iella oxytoca]] is indole-positive whereas [[Klebsiella pneumoniae]] and [[Klebsiella aerogenes]] are indole-negative
-***[[Citrobacter species|''Citrobacter'' species]]: ''[[Citrobacter koseri]]'' is indole positive where as ''[[Citrobacter freundii]]'' is indole negative
+***[[Citrobacter species]]: [[Citrobacter koseri]] is indole-positive where as [[Citrobacter freundii]] is indole-negative
-***[[Proteus species|''Proteus'' species]]: ''[[Proteus vulgaris]]'' is indole positive whereas ''[[Proteus mirabilis]]'' 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