Sample Information Hair and scales from both the periphery and center of the lesion should be used. Broken, frayed, or distorted hairs and those that fluoresce with Wood's light are the best specimens.
Instructions for Use
Select hair and scales for culture.
Remove only a small portion of hair and scales from the lesion with a hemostat or thumb forceps. Avoid placing large amounts of hair and scales on the medium; this will produce useless overgrowth of the contaminants.
Remove the cap from the FUNGASSAY® Dermatophyte Test Medium bottle. Take care to avoid contamination.
Press the hair and scales on the culture medium to ensure good contact, but do not bury the specimen in the medium.
When replacing the cap, make certain that it remains loose so that air exchange can occur in the bottle during incubation. When the cap is too tight color change will not develop.
Identify the bottle with the patient and date.
Incubate at room temperature (22° to 29°C; 72° to 86°F) so that suitable growth will occur.
Evaluate test results as early as 48 hours after inoculation.
Note: Washing of the site is indicated only in cases of heavy contamination or encrustation. If the site is washed before sampling, a nonmedicated, nonfungicidal soap is recommended, followed by drying with an absorptive material. These steps remove saprophytic organisms which could overgrow the culture, thus masking the growth of pathogenic fungi.
FUNGASSAY® provides a simple, rapid, and practical method for confirming diagnosis of dermatophyte infections. FUNGASSAY® is based on a color change within the medium from amber to red. The change is caused by the growth of pathogenic fungi, such as Microsporum and Trichophyton species. These fungi cause most of the dermatomycoses in veterinary medicine.
Evaluation of the test results can begin as early as 48 hours after inoculation. A pinkish color will appear in the amber medium under the specimen and developing colony. The color will intensify as growth proceeds and is due to alkaline metabolites produced by the dermatophytes. When a positive dermatophyte infection is present, the entire medium will turn red by the 7th to 14th day. If there is no growth within 10 days, redistribute the sample on the medium. Occasionally, growth does not occur because of improper inoculation.
A color change may occasionally be produced by a specimen heavily contaminated with saprophytic fungi or bacteria. However, differentiation from dermatophytes can be made as follows:
Dermatophyte: A color change appears in the medium with colony growth—colony pigments are usually light colored.
Saprophyte fungi: Colony growth is well established before any color change appears in the medium—colony pigments are usually dark colored.
Bacteria: The morphology of bacterial colonies differs from the morphology of fungal colonies.