Airborne Escherichia coli (E. coli) in the poultry environment can migrate inside and outside houses through air movement. The airborne E. coli, after settling on surfaces, could be re-aerosolized or picked up by vectors (e.g., caretakers, rodents, transport trucks) for further transmission. To assess the impacts of airborne E. coli transmission among poultry farms, understanding the survivability of the bacteria is necessary. The objective of this study is to determine the survivability of airborne E. coli, settled E. coli, and E. coli in poultry litter under laboratory environmental conditions (22–28 °C with relative humidity of 54–63%). To determine the survivability of airborne E. coli, an AGI-30 bioaerosol sampler (AGI-30) was used to collect the E. coli at 0 and 20 min after the aerosolization. The half-life time of airborne E. coli was then determined by comparing the number of colony-forming units (CFUs) of the two samplings. To determine the survivability of settled E. coli, four sterile Petri dishes were placed on the chamber floor right after the aerosolization to collect settled E. coli. The Petri dishes were then divided into two groups, with each group being quantified for culturable E. coli concentrations and dust particle weight at 24-h intervals. The survivability of settled E. coli was then determined by comparing the number of viable E. coli per milligram settled dust collected in the Petri dishes in the two groups. The survivability of E. coli in the poultry litter sample (for aerosolization) was also determined. Results show that the half-life time of airborne E. coli was 5.7 ± 1.2 min. The survivability of E. coli in poultry litter and settled E. coli were much longer with the half-life time of 15.9 ± 1.3 h and 9.6 ± 1.6 h, respectively. In addition, the size distribution of airborne E. coli attached to dust particles and the size distribution of airborne dust particles were measured by using an Andersen impactor and a dust concentration monitor (DustTrak). Results show that most airborne E. coli (98.89% of total E. coli) were carried by the dust particles with aerodynamic diameter larger than 2.1 µm. The findings of this study may help better understand the fate of E. coli transmitted through the air and settled on surfaces and evaluate the impact of airborne transmission in poultry production.

HighlightsThe study demonstrated a methodology to evaluate bioaerosol samplers on collecting Escherichia coli (E. coli) carried by airborne dust.A dry-base aerosolization system was developed for the study.The sampling efficiency of Andersen six-stage impactor and AGI-30 outperformed that of ACD-200 Bobcat.Airborne E. coli might be preferentially aggregated on large particles (> 7.0 µm).Abstract. Pathogenic Escherichia coli (E. coli) are frequently recovered in poultry litter and may be transmitted through the air after bird activities create airborne dust. To assess risks of airborne transmission of E. coli carried by dust, efficient bioaerosol samplers under dry aerosolization conditions are required. The objective of this study was to compare the performance of three commonly used bioaerosol samplers, which included an Andersen six-stage impactor, an all-glass impinger (AGI-30), and an ACD-200 Bobcat (Bobcat), for collecting the airborne E. coli carried by dust particles under dry aerosolization condition in a bio-safety chamber. A dry aerosolization system was designed to generate dry bioaerosols for the study. Under the same airborne E. coli concentration with stable environmental conditions including temperature and relative humidity (RH), the E. coli concentrations determined by the three samplers were 5.05±2.08 log10 colony-forming units (CFU) m-3, 5.69±1.92 log10 CFU m-3, and 2.69±0.81 log10 CFU m-3 for Andersen six-stage impactor, AGI-30, and Bobcat, respectively. The results showed that there is no significant difference between Andersen six-stage impactor and AGI-30, while there was a sizeable decrease in the bacteria concentration determined by the Bobcat sampler. The results also showed that airborne E. coli were preferentially aggregated on large particles (> 7.0 µm). This study demonstrated a methodology to evaluate bioaerosol sampler efficiency using dry-base carriers of biological agents which are predominant in poultry houses. The optimal sampler can be used to determine the airborne E. coli loading in commercial poultry houses. Keywords: Airborne transmission, Bioaerosol samplers, Dry aerosolization, E. coli, Poultry.

Perovskite nanoparticles of La 1−x Ca x CoO 3 (x = 0, 0.2, 0.3, 0.5) were synthesized by the combustion method using polyvinyl alcohol (PVA) and corresponding metal nitrates. Microstructure of samples was characterized by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) combined with x-ray diffraction (XRD). The nanoparticles were characterized by thermogravimetric and differential thermal analysis (TG-DTA) and BET (Brunauer-Emmet-Teller). A high surface area (15-21 m 2 g −1 ) at low temperature (600 °C) of samples was obtained. The optimal preparative conditions were PVA/metals 2:1 by mole, pH = 3 and 80 °C for gel formation. Perovskites exhibit a good catalytic activity in total oxidation of CO at the low temperature (<250 °C) of reaction.

No abstract

No abstract