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Submitted to: Aerosol Science and Technology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/25/2015 Publication Date: 1/5/2016 Publication URL: https://handle.nal.usda.gov/10113/62021 Citation: Dungan, R.S., Leytem, A.B. 2016. Recovery of culturable of Escherichia coli O157:H7 during operation of a liquid-based bioaerosol sampler. Aerosol Science and Technology. 50(1):71-75. Interpretive Summary: Airborne pathogens can be harmful to humans and livestock if inhaled or ingested after landing on food crops, surface waters, and fomites. To determine the concentration of airborne microorganisms, liquid-based bioaerosol samplers are often used. However, the collection fluid which entraps the microorganisms can affect their viability and subsequent ability to be cultured. In this study we assessed the recovery of pathogenic E. coli from various collection fluids, ranging from deionized (DI) water to DI water containing a low concentration of a soluble organic such as peptone and betaine. Recoveries of E. coli were greatest when soluble organics were used during operating runtimes up to 90 min. Improving the recovery of microorganisms from collection fluids can help increase the accuracy of results obtained from bioaerosol samplers. Technical Abstract: Collection fluids used in liquid-based bioaerosol samplers can influence the viability of microorganisms. In this study we determined the recovery efficiency of vegetative E. coli O157:H7 cells that were spiked into low viscosity evaporating collection fluids during operation of a BioSampler™ for up to 90 min at room temperature. The collection fluids tested were distilled (DI) water, phosphate-buffered saline (PBS) and osmoprotectants consisting of peptone and/or antifoam or betaine at 0.1% (w/w) in DI water. Using DI water, there was a rapid decline in the recovery of culturable E. coli, with only 11, 3, and 0% being recovered after 30, 60, and 90 min, respectively. Recoveries were substantially greater with use of PBS (53, 25, and 16%, respectively) but not as high as with use of the osmoprotectants. Peptone solutions, which are commonly used in liquid-based bioaerosol samplers, allowed for the recovery of 87% of the E. coli after 90 min. However, the control data indicate that some cellular growth did occur, which could be offsetting the recovery of culturable E. coli towards slightly higher values. When an antifoaming agent was added to the peptone solution there was little overall change in the amount of E. coli recovered. Betaine was also determined to be an effective osmoprotectant, with 101, 77, and 41% of E. coli recovered from the impingers at 30, 60, and 90 min, respectively. The results from this study support the incorporation of osmoprotectants in collection fluids, but not use of DI water and PBS, when BioSampler runtimes up to 90 min will be utilized. Runtimes longer than 30 min are sometimes necessary when the airborne concentration of a target organism is low and one is trying to increase the probability of detection. |
