Table 13A: Interpretation of the Enterotube II.

Compartment Reaction Negative Positive
1 glucose fermentation red/orange yellow
1 gas production wax not lifted wax lifted
Remarks: Glucose - Any degree of yellow is positive. Acid end products from glucose fermentation turn the pH indicator from red (alkaline) to yellow (acid).
Remarks: Gas - Positive is a definite and complete separation of the white wax overlay from the surface of the glucose medium. Detects gas from glucose fermentation.

Compartment Reaction Negative Positive
2 lysine decarboxylase activity yellow purple
Remarks: Any degree of purple is positive. Alkaline end products from the decarboxylation of lysine changes the pH indicator from pale yellow (acid) to purple (alkaline).

Compartment Reaction Negative Positive
3 ornithine decarboxylase activity yellow purple
Remarks: Any degree of purple is positive. Alkaline end products from the decarboxylation of ornithine changes the pH indicator from pale yellow (acid) to purple (alkaline).

Compartment Reaction Negative Positive
4 hydrogen sulfide production beige black
4 indole production (done last) colorless red
Remarks: Hydrogen sulfide - Only a true black is positive. Reduction of thiosulfate produces hydrogen sulfide which reacts with iron salts to produce black ferric sulfide.
Remarks: Indole - This test is not interpreted until all other compartments have been read. Kovac's Reagent must be added before reading. Indole, produced from the breakdown of tryptophan, reacts with Kovac's reagent turning it red.

Compartment Reaction Negative Positive
5 adonitol fermentation red yellow
Remarks: Any degree of yellow is positive. Acid end products from adonitol fermentation turn the pH indicator from red (alkaline) to yellow (acid).

Compartment Reaction Negative Positive
6 lactose fermentation red yellow
Remarks: Any degree of yellow is positive. Acid end products from adonitol fermentation turn the pH indicator from red (alkaline) to yellow (acid).

Compartment Reaction Negative Positive
7 arabinose fermentation red yellow
Remarks: Any degree of yellow is positive. Acid end products from adonitol fermentation turn the pH indicator from red (alkaline) to yellow (acid).

Compartment Reaction Negative Positive
8 sorbitol fermentation red yellow
Remarks: Any degree of yellow is positive. Acid end products from adonitol fermentation turn the pH indicator from red (alkaline) to yellow (acid).

Compartment Reaction Negative Positive
9 (not normally used) Voges-Proskauer colorless red
Remarks: This test is not used unless required later as a confirmatory test. Acetoin produced during the production of butylene glycol from glucose fermentation reacts with the added reagents KOH and alphanaphthol and turns red.

Compartment Reaction Negative Positive
10 dulcitol fermentation not yellow yellow
10 phenylalanine deaminase activity not black/smoky gray black/smoky gray
Remarks: Dulcitol - Yellow or pale yellow is positive. Any other color is negative. Acid from dulcitol fermentation turns the pH indicator from green (alkaline) to yellow (acid).
Remarks: PA - Pyruvic acid produced from deamination of phenylalanine reacts with ferric salts in the medium turning it black.

Compartment Reaction Negative Positive
11 urea hydrolysis beige red/purple
Remarks: Hydrolysis of urea forms ammonia which causes the pH indicator to turn from yellow (acid) to pink, red, or purple (alkaline).

Compartment Reaction Negative Positive
12 citrate utilization green blue
Remarks: Any degree of blue is positive. Utilization of citrate produces alkaline products turning the pH indicator from green (acid) to blue (alkaline).


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Microbiology Laboratory Manual by Gary E. Kaiser, PhD, Professor of Microbiology
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Last updated: September, 2017