MOELLERS DECARBOXYLASE MEDIA

Cat. no. Y41 Moellers Decarboxylase Base, 16x125mm Tube, 5ml 20 or 100 tubes/box
Cat. no. Y42 Moellers Arginine Decarboxylase, 16x125mm Tube, 5ml 20 or 100 tubes/box
Cat. no. Y43 Moellers Lysine Decarboxylase, 16x125mm Tube, 5ml 20 or 100 tubes/box
Cat. no. Y44 Moellers Ornithine Decarboxylase, 16x125mm Tube, 5ml 20 or 100 tubes/box

INTENDED USE

Hardy Diagnostics Moellers Decarboxylase Media is recommended for the differentiation of gram-negative enteric bacilli based on the production of arginine dihydrolase, lysine decarboxylase or ornithine decarboxylase.

SUMMARY

Hardy Diagnostics Moellers Decarboxylase Media employs the formula established by Moeller, who, in 1955, first introduced its use in the differentiation of gram-negative enteric bacilli. (6) The basal media consists of peptones, beef extract, pyridoxal, glucose, bromcresol purple and cresol red. Necessary growth nutrients are supplied by the peptones and beef extract. Pyridoxal is an enzyme co-factor. Bromcresol purple and cresol red serve as pH indicators that aid in the detection of glucose-fermentation and amino acid decarboxylation. Arginine, lysine or ornithine are added to the basal medium to detect the production of specific amino acid decarboxylase and dihydrolase enzymes.

The production of decarboxylase and dihydrolase enzymes is induced in an acidic environment. In the case of Moeller Decarboxylase Media, an acidic state is established when glucose is fermented by the microorganism resulting in a color shift from purple to yellow. Microorganisms possessing the specific decarboxylase and dihydrolase enzymes for the amino acid (arginine, lysine or ornithine) degrade the amino acid to yield various amine by-products. An alkaline environment is thereby established. The increased pH results in a color shift from the previous yellow to a purple or gray-purple. If the organism does not produce the appropriate enzyme, then the medium will retain the yellow color indicative of glucose-fermentation. Non-glucose-fermenters that possess decarboxylase and dihydrolase enzymes may display weak decarboxylase activity to produce little or no color change as compared to an uninoculated tube of basal medium.

FORMULA

Ingredients per liter of deionized water:*

Moellers Decarboxylase Base:
Peptone 5.0gm
Beef Extract 5.0gm
Glucose 0.5gm
Bromcresol Purple 10.0mg
Cresol Red 5.0mg
Pyridoxal 5.0mg

Additionally,

Moellers Arginine Decarboxylase contains:
Arginine 10.0gm

Moellers Lysine Decarboxylase contains:
Lysine 20.0gm

Moellers Ornithine Decarboxylase contains:
Ornithine 10.0gm

Final pH 6.0 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.

STORAGE AND SHELF LIFE

Storage: Upon receipt store at 2-30ºC. away from direct light. Media should not be used if there are any signs of deterioration, discoloration, contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.

PRECAUTIONS

PROCEDURE

Specimen Collection: Specimen collection is not applicable since this medium is not intended for primary isolation from clinical specimens. As a general rule, infectious material should be submitted directly to the laboratory without delay and protected from excessive heat and cold. If there is to be a delay in processing, the specimen should be inoculated onto an appropriate transport media and refrigerated until inoculation. Consult listed references for information on specimen collection. (1-5)

Method of Use:

1. Inoculate the media using 1-2 isolated colonies taken from an 18-24 hour pure culture.

2. Inoculate a control tube of Decarboxylase Base (Cat. no. Y41) in parallel with the amino acid based media.

3. Overlay each inoculated tube with 1ml sterile mineral oil (Cat. no. Z80).

4. Tighten the caps on the inoculated tubes and incubate aerobically at 35ºC. for 18-96 hours.
Note: Increased incubation for up to 10 days may be necessary for some microorganisms.

5. Observe daily for color reactions. Compare results with the inoculated control tube.

INTERPRETATION OF RESULTS

A positive decarboxylase result is indicated by the development of a purple to pale yellow-purple color.

A negative decarboxylase result is indicated by the development of a bright yellow color for glucose-fermenting microorganisms. Non-glucose-fermenters will result in little or no color change as compared to an uninoculated tube.

LIMITATIONS

Mineral oil must be applied to the surface of each inoculated medium. Oil overlay decreases the possibility of an alkaline shift occurring in the medium due to oxidation.

Test interpretation should not be made prior to 18-24 hours of incubation. Earlier interpretation may lead to erroneous results. Glucose-fermentation occurs within the first 10-12 hours of incubation. Fermentation produces an acidic environment which results in a yellow color development. The production of decarboxylase and dihydrolase enzymes will not be induced until the acidic state has been established.

Decarboxylation results for non-glucose-fermenting microorganisms may prove unreliable. This test relies on the inducement of decarboxylase and dihydrolase enzymes by acid produced from glucose-fermentation. Decarboxylation results for non-glucose-fermenting microorganisms, therefore, may display weak decarboxylase activity thereby resulting in an insufficient production of amines necessary to convert the pH indicator system. Some non-fermenters, however, will produce sufficient amines and result in a deeper purple color as compared to an uninoculated tube of basal medium.

Non-glucose-fermenting microorganisms that do not produce the appropriate enzyme remain the same color as the original uninoculated control tube of basal medium.

Organisms that do not produce the appropriate enzyme, but do utilize glucose, will result in a yellow color development in the medium.

Development of a purple (alkaline) color in the uninoculated control tube of basal medium invalidates all test results, and test interpretation should not be made.

Increased incubation for up to 10 days may be necessary for some microorganisms.

MATERIALS REQUIRED BUT NOT PROVIDED

Standard microbiological supplies and equipment such as loops, other culture media, swabs, applicator sticks, mineral oil, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.

QUALITY CONTROL

Test Organisms
Inoculation Method*
Incubation
Results
Time
Temperature
Atmosphere
Klebsiella pneumoniae
ATCC ® 13883
E** 24-96hr 35°C Aerobic Growth;
Arginine: negative,
Lysine: positive,
Ornithine: negative


Enterobacter cloacae
ATCC ® 23355
E** 24-96hr 35°C Aerobic Growth;
Arginine: positive, Lysine: negative,
Ornithine: positive

Proteus mirabilis
ATCC ® 12453
E** 24-96hr 35°C Aerobic Growth;
Arginine: negative,
Lysine: negative,
Ornithine: positive


User Quality Control

PHYSICAL APPEARANCE

Moellers Decarboxylase Media should appear clear, slightly opalescent, and yellowish-red in color.

K. pneumoniae growing in Moellers Decarboxylase Media

Klebsiella pneumoniae (ATCC ® 13883) growing in Moellers Decarboxylase Media. Incubated aerobically with sterile mineral oil (Cat. no. Z80) layer and tightened caps for 24 hours at 35ºC.
Pictured: Moellers Base (Cat. no. Y41), Moellers Arginine (Cat. no. Y42), Moellers Lysine (Cat. no. Y43), Moellers Ornithine (Cat. no. Y44).

E. cloacae growing in Moellers Decaboxylase Media

Enterobacter cloacae (ATCC ® 23355) growing in Moellers Decaboxylase Media. Incubated aerobically with sterile mineral oil layer (Cat. no. Z80) and tightened caps for 24 hours at 35ºC.
Pictured: Moellers Base (Cat. no. Y41), Moellers Arginine (Cat. no. Y42), Moellers Lysine (Cat. no. Y43), Moellers Ornithine (Cat. no. Y44).



P. mirabilis growing in Moellers Decarboxylase Media

Proteus mirabilis (ATCC ® 12453) growing in Moellers Decaboxylase Media. Incubated aerobically with sterile mineral oil layer (Cat. no. Z80) and tightened caps for 24 hours at 35ºC.
Pictured: Moellers Base (Cat. no. Y41), Moellers Arginine (Cat. no. Y42), Moellers Lysine (Cat. no. Y43), Moellers Ornithine (Cat. no. Y44).

Moellers Decarobxylase Base

Uninoculated tube of Moellers Decaboxylase Base (Cat. no. Y41).






REFERENCES

1. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

2. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

3. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

4. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

5. Koneman, E.W., et al. Color Atlas and Textbook of Diagnostic Microbiology, J.B. Lippincott Company, Philadelphia, PA.

6. Moeller. 1955. Acta Pathol. MIcrobiol. Scand.; 36:158.


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032816gr