PRINCIPLE/DISCUSSION:

Rapid Fermentation Tablets are used in identifying fermentative bacteria through their ability to ferment carbohydrates and related compounds. Fermentation of the related carbohydrate creates acid changing the phenol red indicator to yellow. The long shelf life offered in this system makes it easy to do supplemental testing without the high costs normally associated with rare sugars in tube form. These tablets are designed for use with coliform bacteria only.

ACTIVE INGREDIENTS:

Each tablet contains the respective carbohydrate in a final concentration of 20 mg. per tablet and other inert chemicals: Dipotassium phosphate, Phenol Red, Hyamine, and Sodium Chloride. None of the ingredients are known to be hazardous.

STORAGE:

Store tablets with desiccant at room temperature up to 80o F.

MATERIALS REQUIRED:

Each carbohydrate is sold separately in bottles of 50 tablets. The complete list of available carbohydrates is given in the QUALITY CONTROL section. Rapid Fermentation tests require fresh 24 hour growth on culture media. Consult the Manual of Clinical Microbiology for recommended media for the specimen. The tests may be done from any media if sufficient colonies are available. The following items are required but not provided:
Small test tubes (e.g. 12 X 75)
Inoculating loop
Sterile pipette
Distilled water, pH 7.0-7.2

PROCEDURE:

For the correct carbohydrate selection, consult the Manual of Clinical Microbiology. Follow instructions for single or multiple tests as shown below.

SINGLE TEST METHOD -

Harvest enough colonies of the organism to create a heavy bacterial suspension in 1.5- 2.0 ml of distilled water and add the tablet. Add oil overlay if desired. Incubate at 37oC.

MULTIPLE TEST METHOD -

Label and set up the desired number of empty tubes in a rack. Add 1.5 to 2.0 ml of distilled water (neutral pH) and the appropriate tablet to each tube. Prepare a heavy suspension into 1.0-2.0 ml. of distilled water from an agar slant or plate containing a pure culture of the organism being tested. This is enough to inoculate 9-12 tubes and still yield rapid results. The suspension may be used for up to 4 days if stored at 4oC. Inoculate the prepared tubes by adding 2-3 drops of this suspension with a sterile pipette. Add oil overlay if desired. Incubate at 37oC.

INTERPRETATION OF RESULTS

The tube should be observed for color change from red to yellow, indicating acid production. Fermentation may be apparent in 30 minutes and usually is complete within 6 hours. It is best to hold tubes for 48 hours before discarding negative tests. Gas production is shown by the appearance of bubbles near the bottom of the tube.

QUALITY CONTROL:

KEY Fermentation tablets should be tested prior to use with organisms which produce known reactions. Suggestions are listed below. The Manual of Clinical Microbiology