| The ability to measure the concentration of airborne bacteria accurately and reliably is of growing public health importance. The present document contains two studies that evaluate the influence methods of generation, sampling, and environmental conditions have on the viability and culturability of the vegetative bacterium (Pantoea agglomerans (P. a. )). A third field study evaluates an intervention to reduce particulate matter (PM), bioaerosols and ammonia inside a concentrated animal feeding operation (CAFO).; In the first study, culturability alone was examined as a function of generation method (Collison and Bubble nebulizers), sampler (AGI-30 and SKC Biosampler), collection media (water and phosphate buffered saline (PBS)), and across a range of humidities (RH). A sample from the generator fluid before and after 10 min of operation, showed the bubble nebulizer yields 15% higher viability relative to the Collison nebulizer. When aerosol generated by the nebulizers was sampled, a nonsignificant increase (22%) in culturable counts was observed for the bubble generator relative to the Collison (p=0.09). PBS as collection fluid was found to increase culturability by 10% compared with sterile deionized water (p<0.01). Humidity was shown to strongly influence culturability with CFU below detection at RH < 15% and a log-linear increase from 15 to 75% RH.; In the second study, flow cytometry was validated and then employed to examine the influence of sampler (AGI-30, SKC Biosampler(TM), and polycarbonate membrane filter) and sampling duration (10 to 60 min) on total bacterial counts, and on viability and culturability of bacteria. After 60 minutes of pulling filtered air through a P. a. doped filter, filter extraction, viability, and culturability were 50%, 13%, and 5%, respectively. After 60 minutes, the Biosampler had retention, survivability, and culturability recoveries of 75%, 55%, and 50%. The AGI-30 showed recoveries of 30%, 15%, and 5%, respectively.; In the third study the effectiveness of the intervention was evaluated by comparing air quality from before to after treatment and between treated and untreated sides of a barn separated by an impervious partition. On the untreated side, air quality was typical for a swine CAFO with mean PM 2.5 of 0.28 mg/m3 and PMTOT of 1.5 mg/m 3. The treatment yielded a reduction in PM concentration from 75-90% from before to after treatment. Effectiveness increased with time, application, and particle size (40% reduction for 1 mum and 90% for >10 mum). Airborne bacteria levels (total bacteria, Enterobacteriaceae and gram-positive cocci) decreased one log10 after treatment. In contrast, treatment had no effect on ammonia concentrations.; Together these study results are significant in establishing new experimental procedures for evaluating bioaerosol sampler performance, identifying limitations with current methods of sampling and analysis, and in demonstrating the effectiveness of an intervention in yielding exposure and emission reductions at a swine CAFO. |
