Indole Test
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Indole Test Done by: alkaser40
Indole Test The test: •
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Pure bacterial culture must be grown in sterile tryptophan or peptone broth for 24-48 hours before performing the test. Following incubation, add 5 drops of Kovac's reagent (isoamyl alcohol, p-Dimethylaminobenzaldehyde, concentrated hydrochloric acid) to the culture broth. A variation on this test using Ehrlich's reagent (using ethyl alcohol in place of isoamyl alcohol, developed by Paul Ehrlich) is used when performing the test on nonfermenters and anaerobes. A positive result is shown by the presence of a red or red-violet color in the surface alcohol layer of the broth. A negative result appears yellow. A variable result can also occur, showing an orange color as a result. This is due to the presence of skatole, also known as methyl indole or methylated indole, another possible product of tryptophan degradation. Indole-Positive Bacteria Bacteria that test positive for cleaving indole from tryptophan include: Aeromonas hydrophilia, Aeromonas punctata, Bacillus alvei, most Citrobacter sp., Edwardsiella sp., Escherichia coli, Flavobacterium sp., Haemophilus influenzae, most Proteus sp. (not P. mirabilis), Plesiomonas shigelloides, Pasturella multocida, Pasturella pneumotropica, Streptococcus faecalis, and Vibrio sp. Indole-Negative Bacteria Bacteria which give negative results for the indole test include: Actinobacillus spp., Aeromonas salmonicida, Alcaligenes sp., most Bacillus sp., Bordtella sp., Enterobacter
Indole Test Purpose: • The indole test performed on bacterial species to determine the ability of the organism to split indole from the amino acid tryptophan. This division is performed by a chain of a number of different intracellular enzymes, a system generally referred to as "tryptophanase."
Indole Test Methods: 3.Inoculate the tryptophan broth with the test organism and incubate at 37°C for 24-28h. 4.Add 0.5mL of the Kovac’s reagent and gently agitate. 5.Examine the upper layer of liquid
Indole Test • Results: • Positive result red colour (occurring within a few seconds) • Negative result yellow colour
Indole Test The test: •
•
•
• •
• •
Pure bacterial culture must be grown in sterile tryptophan or peptone broth for 24-48 hours before performing the test. Following incubation, add 5 drops of Kovac's reagent (isoamyl alcohol, p-Dimethylaminobenzaldehyde, concentrated hydrochloric acid) to the culture broth. A variation on this test using Ehrlich's reagent (using ethyl alcohol in place of isoamyl alcohol, developed by Paul Ehrlich) is used when performing the test on nonfermenters and anaerobes. A positive result is shown by the presence of a red or red-violet color in the surface alcohol layer of the broth. A negative result appears yellow. A variable result can also occur, showing an orange color as a result. This is due to the presence of skatole, also known as methyl indole or methylated indole, another possible product of tryptophan degradation. Indole-Positive Bacteria Bacteria that test positive for cleaving indole from tryptophan include: Aeromonas hydrophilia, Aeromonas punctata, Bacillus alvei, most Citrobacter sp., Edwardsiella sp., Escherichia coli, Flavobacterium sp., Haemophilus influenzae, most Proteus sp. (not P. mirabilis), Plesiomonas shigelloides, Pasturella multocida, Pasturella pneumotropica, Streptococcus faecalis, and Vibrio sp. Indole-Negative Bacteria Bacteria which give negative results for the indole test include: Actinobacillus spp., Aeromonas salmonicida, Alcaligenes sp., most Bacillus sp., Bordtella sp., Enterobacter
Indole Test Purpose: • The indole test performed on bacterial species to determine the ability of the organism to split indole from the amino acid tryptophan. This division is performed by a chain of a number of different intracellular enzymes, a system generally referred to as "tryptophanase."
Indole Test Methods: 3.Inoculate the tryptophan broth with the test organism and incubate at 37°C for 24-28h. 4.Add 0.5mL of the Kovac’s reagent and gently agitate. 5.Examine the upper layer of liquid
Indole Test • Results: • Positive result red colour (occurring within a few seconds) • Negative result yellow colour
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