CANDIDA SCREEN- K9141B -

PRINCIPLES/DISCUSSION:

Candida albicans produces enzymes which hydrolyze specific substrates bound to compounds which are fluorescent or colorimetric when free. The hydrolysis of the substrate will produce end products, one visible under ultraviolet light and the other after addition of a developer. Candida screen, by combining two non-interfering substrates (4-Mu-N-acetyl B-d Galactosaminide, and Proline naphthylamide), allows presumptive identification of C. albicans in 15 minutes. Candida albicans is positive for both of these substrates, while other commonly encountered yeasts are negative for one or both.

MSDS / STORAGE

None of the ingredients is hazardous in the minute amounts present in each disc. Uninoculated tubes may be discarded in normal trash. The developer contains hydrochloric acid, will stain surfaces and hands, and is corrosive.

Store all materials in the refrigerator between uses. It is not necessary to bring discs or reagent to room temperature before use.

MATERIALS REQUIRED:

Discs are sold 50 per bottle with PEP reagent provided. Usage requires pure 24 hour culture on appropriate media. The following items are also required but not provided:

Loops for harvesting colonies

Distilled water, neutral pH

Woods lamp

PROCEDURE:

1) Place a disc onto a slide or into a small test tube.

2) Add 1-2 drops of distilled water to the tube containing the disc or moisten the disc slightly on the slide..

3) Inoculate using 3-5 colonies harvested from a fresh 24 hour pure culture taken from a plate or slant. Mix thoroughly. If using a slide smear with the organism.

4) Incubate for 15 minutes.

INTERPRETATION:

1)The first reaction is fluorescent. Read under a Woods lamp, looking for bright blue fluorescence. Disregard any other color of fluorescence which may appear in rare circumstances. A bright blue fluorescence indicates that the organism has hydrolized the 4 MU-N-Acetyl-

b-d-galactosaminide.

2) Perform the second test by adding 1 drop of PEP reagent to the tube and reincubating for 5 minutes.

A positive test will turn red or deep pink on the disc. The liquid in the test tube may or may not show the red color-observe the disc only. Red color indicates that the organism has hydrolyzed the Proline Naphthylamide.

3) If both tests are positive, you may make a presumptive identification of Candida albicans. Other yeasts will be negative for either or both of the tests.

LIMITATIONS:

Candida screen is part of an overall program for identification of yeasts, and only provides a high probability for presumptive separation of C. albicans from other yeasts. For specific identification, additional testing is required. Mixed cultures may produce unreliable results, as may cultures less than 18-24 hours or more than 72 hours old.

QUALITY CONTROL:

For quality control, Key Scientific Products recommends using Candida albicans, ATCC 60193 and Candida krusei ATCC 6258.

REFERENCES/FOOTNOTES:

1. Dealler, S.F. Candida albicans colony identification in 5 minutes in a general microbiology laboratory. J. Clin. Microbiol. 29: 1081-1082, 1991

2. Finegold, S. and E. Baron. 1986. Diagnostic Microbiology. 7th Ed. C.V. Mosby. St Louis.

3. Lennette, E.H. et al. 1985. Manual of Clinical Microbiology. 4th Ed. ASM. Washington, D.C.

4. Perry, J.L., G.R. Miller. Umbelliferyl-labeled galactosaminide as an aid in identification of

Candida albicans. J. Clin Microbiol 25: 2424-2425, 1987.

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