Rhodotorula, an allergenic yeast genus, was previously identified from viable air samples; however, the daily exposure to this allergen is not known. This study characterizes the frequency, concentration, and meteorological variables associated with airborne Rhodotorula.
Burkard 7-day spore trap air samples were collected in Tulsa, Oklahoma during 2015. DNA was extracted from daily samples and quantified with a TaqMan Rhodotorula assay. The daily concentrations (cells per cubic meter) of Rhodotorula were calculated using a standard curve of known yeast cell concentrations. Rhodotorula concentrations and meteorological variables were analyzed by multiple regression to identify which independent variables explained a significant amount of the variation in the dependent variable.
RESULTS: Quantitative PCR indicated that Rhodotorula occurred in the Tulsa atmosphere on 55% of the days in 2015. There were 62 days with a concentration of 1 cell/m3 and 140 days >1 cell/m3. The frequency of Rhodotorula in winter, spring, summer, and autumn was 66%, 41%, 73%, and 29%, respectively. The average daily concentration was 4 cells/m3 with a range from 0 to 715 cells/m3. The seasonal average daily concentrations were 3, 3, 8, and 2 cells/m3 for winter, spring, summer, and autumn, respectively. The two significant predictors identified in the multiple regression model (R2=.03, F(4,360)=3.87, p=.004) were average relative humidity (β=-.11, p=.04) and soil moisture at 25 cm (β=-.14, p=.009).
Rhodotorula occurs frequently in daily air samples typically at low concentrations and is associated with relative humidity and soil moisture. More work is needed to determine the environmental exposure to other airborne yeasts.