Identification and Possible Disease Mechanisms of an Under-Recognized Fungus, <i>Aureobasidium pullulans</i>

Abstract

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.

Phenotypic plasticity in fungi: a review with observations onAureobasidium pullulans

“…It has been found in most habitats and is prominent in the phyllosphere. It is also airborne (Shelton et al 2002 and has been implicated as a major cause of allergic disease in humans; recent studies on conidia emitted from flowers suggest high-molecular weight allergens in A. pullulans are responsible (Taylor et al 2005). Aureobasidium pullulans has been used for the production of extracellular compounds, especially polysaccharides such as pullulan (Catley 1979) and enzymes (Buzzini and Martini 2002).…”

“…Aureobasidium pullulans is involved as the principal colonizer initiating biodeterioration (e.g. plasticized polyvinyl chloride, Webb et al 2000) has been used as an indicator of environmental pollution (Deshpande et al 1992) and is implicated in human disease (Taylor et al 2005).…”

Seasonal Variability of Culturable Fungal Genera in the House Dust of Inner-City Residences

“…A study conducted in Germany showed that this genus was associated with hypersensitivity pneumonitis, (59) and Taylor et al (60) reported that 16 out of 94 patients at the Asthma and Allergy Center in Pasadena, California, had a positive skin test reaction to A. pullulans extract. Stark et al (11) reported that high levels of Aureobasidium (>24,000 CFU/g or >90th percentile concentration for that study) were associated with allergic rhinitis in 5-year-old children.…”

Emergence of Aureobasidium pullulans as human fungal pathogen and molecular assay for future medical diagnosis

“…have been described as yeast-like fungi, which produce yeast-like hyaline conidia and a filamentous growth form (Taylor et al 2006). This genus was established in 1891 by French scientists Viala and Boyer (Cooke 1959).…”