What does spot indole test for?
Objective of Spot Indole Test To determine the ability of organism for the production of indole by the action of tryptophanase enzyme.
What is a positive indole test?
A positive indole test is indicated by the formation of a red color in the reagent layer on top of the agar deep within seconds of adding the reagent. If a culture is indole negative, the reagent layer will remain yellow or be slightly cloudy.
What bacteria can produce indole?
many pathogenic bacteria such as Bacillus alvei, pathogenic E. coli, several Shigella strains, Enterococcus faecalis, and V. cholerae, can produce indole.
Which Enterobacteriaceae are indole positive?
Summary of biochemical reactions of Enterobacteriaceae
| TSI | Indole | |
|---|---|---|
| E.coli | A/A, Gas | +ve |
| Citrobacter freundii | A/A or K/A, Gas, H2S | +ve |
| Klebsiella pneumoniae | A/A, Gas (++), H2S | -ve |
| Enterobacter cloacae | A/A, Gas (++) | -ve |
Is Enterobacter aerogenes indole positive?
E. coli is indole-positive; Enterobacter aerogenes is indole- negative. Glucose is the major substrate oxidized by enteric bacteria for energy production.
Is the indole test selective or differential?
This is a differential medium. It tests the ability of an organism to do several things: reduce sulfur, produce indole and swim through the agar (be motile).
Which media is used in indole test?
The medium used with this reagent is either broth containing tryptophan, motility- indole-ornithine agar, or sulfide-indole-motility agar (SIM).
Where is indole created?
gut microbiota
Indole is produced by gut microbiota from tryptophan, through the tryptophanase enzyme encoded by the tnaA gene. First, we mimicked an acute and high overproduction of indole by injecting this compound in the cecum of conventional rats.
What is indole used for in bacteria?
Indole is an intercellular signal in both gram-positive and gram-negative bacteria and has been shown to control a number of bacterial processes such as spore formation, plasmid stability, drug resistance, biofilm formation, and virulence (Lee & Lee, 2010).
Which medium is used for indole test?
Is Citrobacter Freundii indole positive?
The genus Citrobacter consists of Gram-negative peritrichous rods. The genus is subdivided into two species: (1) Citrobacter freundii (includes mostly H2S-positive, indole-negative, and adonitol-negative cultures) and (2) Citrobacter diversus (composed of H2S-negative, indole-positive, and adonitol-positive cultures).
Is Klebsiella pneumoniae indole positive?
The two clinically relevant species, Klebsiella pneumoniae and Klebsiella oxytoca, are differentiated by the ability to produce indole from tryptophan, K. oxytoca being indole positive.