Identification and possible disease mechanisms of an under-recognized fungus, Aureobasidium pullulans.
BACKGROUND
Investigations into the occurrence and health effects of yeast-like fungi in the outdoor air in the US have been limited. We sought to identify a respirable-sized fungus common in the Pasadena air, locate a major source for the emissions and investigate its relevance to allergic disease.


METHODS
Yeast-like fungi sampled from the environment were isolated, microscopically examined and sequenced. Pasadena allergy patients were skin tested with commercially available fungal extracts. Patient serum was immunoanalyzed for specific IgE reactivity. Nearby vegetation was analyzed in a controlled emission chamber to find a major source for the aerosols.


RESULTS
Hyaline unicellular conidia comprised up to 90% (41,250 m(-3) of air) of total fungal counts and generally peaked at night and during periods of rainfall and ensuing winds throughout the fall and winter. Flowers were determined to be a major source of the emissions. The cellular and colonial morphology of isolates were consistent with Aureobasidium species. The sequence of the D1/D2 region of the 26S ribosomal subunit of isolates from flowers showed identity to two strains of Aureobasidium pullulans (black yeast). Seventeen percent (16/94) of atopic individuals had positive skin testing with A. pullulans extract. Patient sera IgE identified several high molecular weight allergens in Aureobasidium extracts.


CONCLUSIONS
Respirable-sized conidia of A. pullulans are emitted from flowers and form high concentrations in the air. They are associated with immediate reactivity on skin tests, bind to patient sera IgE, and might be relevant in allergic upper and lower airway diseases.
Taylor
Philip E
PE
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA. taylor@caltech.edu
Esch
Robert
R
Flagan
Richard C
RC
House
James
J
Tran
Lisa
L
Glovsky
M Michael
MM
D000391:Air Microbiology; D000485:Allergens / Q000009:adverse effects / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D000908:Antibodies, Fungal / Q000097:blood; D001483:Base Sequence; D002140:California; D002980:Climate; D004784:Environmental Monitoring; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000097:blood / Q000175:diagnosis / Q000209:etiology*; D007073:Immunoglobulin E / Q000097:blood; D008969:Molecular Sequence Data; D025282:Mycelium; D018515:Plant Leaves / Q000382:microbiology; D012331:RNA, Fungal / Q000235:genetics; D012621:Seasons; D012882:Skin Tests; D013170:Spores; D014197:Trees / Q000382:microbiology; D015003:Yeasts / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*
D000485:Allergens; D000908:Antibodies, Fungal; D012331:RNA, Fungal; D007073:Immunoglobulin E