Specimen Requirements:
Isolates must be submitted in pure culture on a slant. Any medium that supports the growth of the organism is acceptable.

Mould Identification CPT 87107

Human and veterinary clinical isolates are identified to the level necessary for appropriate patient management. In some instances species level identification may not be pursued, while in others it may be mandatory for determining the most efficacious therapeutic options. In situations where publications are anticipated, the FTL will make every effort, after discussion with the sender, to provide the most extensive identification possible to meet publication requirements.

Other isolates are identified to the level required after consultation with the referring laboratory.

CPT 87797. Identification of Histoplasma capsulatum var. capsulatum, Blastomyces dermatitidis, and Coccidioides immitis is confirmed by DNA probe.

CPT 87220, 87101, 87107. Specialized testing consisting of KOH, culture, and identification of agents of dermatophytosis or dermatomycosis is offered to the dermatology/podiatry community.

Research activities that may be pursued, after discussion with the sender, and at an additional cost include:

• Identification of isolates by molecular sequencing
• Molecular sequencing for outbreak strain relatedness
• Individually-tailored research projects

The FTL utilizes a variety of tests to arrive at a final yeast identification. Current methods include one or more of the following:

API 20C AUX by bio Merieux
The API 20C AUX is a ready-to-use micromethod which permits the performance of 19 assimilation for the identification of most clinically significant yeasts and yeast-like organisms in the genera Candida, Cryptococcus, Geotrichum, Hansenula, Hanseniaspora, Troulopsis, Trichosporon, Prototheca, Rhodotroula, Saccharomyces, and Sporobolomyces. Assimilation reactions are complete after 72 hours incubation at 30°C
The API 20C System consists of a series of cupules containing dehydrated substrates for assimilation reactions. These substrates are reconstituted by the addition of a pure yeast suspension in API basal medium to the cupules. Assimilation is the utilization of a carbon source by a yeast in the presence of oxygen. The assimilation of a sugar results in a turbid well

Classic Whickerham assimilation and formation
Although the API 20C yeast identification strip is the gold standard for identification of yeast fungi to the species level in clinical laboratories, many isolates continue to elude identification via this method. Classic Wickerham fermentation studies may assist in a definitive identification.
During fermentation, carbohydrates are fermented to form ethanol and carbon dioxide. Sugars that are fermented (accompanied by gas production) are generally assimilated (accompanied by a color change) as well. The reverse, however, is not necessarily true

Cycloheximide susceptibility
Many yeasts are described in taxonomy references regarding their susceptibility to cycloheximide. This test gives one more characteristic, either susceptible or resistant by which to make a definitive identification.

Nitrate assimilation
Yeasts have the ability to use ammonium sulfate, asparagine, peptone, and urea at reasonable concentrations as the sole source of nitrogen when adequate vitamins are provided. In contrast, aliphatic amines, potassium nitrate, sodium nitrate, and some amino acids are utilized selectively by different yeasts. These latter compounds are very useful in the identification of yeasts.

Urea hydrolysis
A number of yeasts produce the enzyme urease, thereby having the capability to hydrolyze urea. The ability to produce urease is determined with Christensen’s urea agar and provides yet another characteristic by which to make an identification.

Macroscopic and microscopic morphology
Macroscopic descriptions are made from yeast colonies grown on Saboraud Dextrose Agar incubated at 30°. The Dalmau plate (Corn Meal Agar) is useful in determining the microscopic morphology of the yeast. Cultures are evaluated for the production of true hyphae, pseudohyphae, blastoconidia, and Arthroconidia.

Temperature Studies
Temperature studies offer additional information which aid in the identification of yeast isolates. For example, Cryptococcus neoformans can be distinguished from other Cryptococcus sp. by its ability to grow at 37° C.

Barnet’s Computer Assisted Key
Barnet’s Computer Assisted Key is a computerized synoptic key by which results of testing from the above listed methods may be entered. Once the test reactions have been entered, the computer searches the database and reveals fungi that have the same reactions. The probability that a listed organism is the correct organism is also listed.

Research activities that may be pursued, after discussion with the sender, and at an additional cost include:

• Identification of isolates by molecular sequencing
• Molecular sequencing for outbreak strain relatedness
• Individually-tailored research projects