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Identification of Viable Cryptococcus neoformans

Category Microbiology Lab (Mold, Bacteria, Legionella, Allergens)
Test Identification of Viable Cryptococcus neoformans
Description

Cryptococcus neoformans (teleomorph: Filobasidiella spp.) is typically recovered from environmental samples as a nondescript yeast. This yeast is endemic throughout the world with different strains predominating in different locales. This yeast thrives in high nitrogen content material and is often associated with bird droppings. Outbreaks are typically associated with some kind of roosting site disturbance.

Cryptococcosis (an infection with Cryptococcus neoformans) is a trademark secondary infection in AIDS patients and most other cases are in patients with some other predisposing condition (such as lupus erythematosus, lymphoma, or leukemia). The infection is started by the inhalation of airborne fungal material and with ensuing infection in the lungs. The disease usually spreads to the brain and meninges, often proving to be fatal.

The main problem with the detection of Cryptococcus neoformans is that it is a nondescript yeast upon primary isolation. While most common indoor fungi can be differentiated to a degree by physical characteristics, yeasts are typically lumped into a single group. The differentiation of C. neoformans from other yeasts is based on biochemistry rather than direct observation and as such requires viable cultures of the organism. The analysis for C. neoformans can be performed in the typical 6-10 day turn around for viable cultures, but the test requires special media that do not allow other fungi to be reliably recovered or identified. Acceptable matrices include both swabs and bulk material are acceptable, as well as Andersen-style plates. For Andersen sampling the IAQ investigator should use Birdseed Agar (BBL) for the isolation medium, as it provides the quickest and most selective recovery of possible C. neoformans.

Analytical Code: M028