Impact of poultry litter Salmonella levels and moisture on transfer of Salmonella through associated in vitro generated dust

Authors: PAL, AMRIT - Auburn University; BAILEY, MATTHEW - Auburn University; TALORICO, AIDAN - Auburn University; KREHELING, JAMES - Auburn University; MACKLIN, KEN - Auburn University; PRICE, STUART - Auburn University; Buhr, Richard - Jeff; BOURASSA, DIANNA - Auburn University

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2021
Publication Date: 5/4/2021
Citation: Pal, A., Bailey, M., Talorico, A.A., Kreheling, J.T., Macklin, K.S., Price, S.B., Buhr, R.J., Bourassa, D.V. 2021. Impact of poultry litter Salmonella levels and moisture on transfer of Salmonella through associated in vitro generated dust. Poultry Science. 100(8):101236. https://doi.org/10.1016/j.psj.2021.101236.
DOI: https://doi.org/10.1016/j.psj.2021.101236

Interpretive Summary: Dust present in poultry houses can contain high concentrations of microorganisms and has the potential to include bacterial pathogens from the litter. The objective of this study was to examine the potential for litter-to-dust transfer of aerobic bacteria, Salmonella, E. coli, and coliforms, and the role of the litter moisture on this process. To evaluate litter-to-dust transfer of bacteria (Experiment 1), used poultry litter in flasks was inoculated with Salmonella. To evaluate the effect of litter moisture on litter-to-dust microbial transfer (Experiment 2), litter was inoculated with Salmonella with increasing amounts of sterilized water was added for moisture adjustment. Dust was generated by blowing air in a direct stream onto inoculated litter while simultaneously collecting dust through impingement. Following litter and dust sample collection, microbial analyses for Salmonella, E. coli, coliforms, and aerobic plate counts (APC) were conducted. Both experiments were repeated five times. In experiment 1, APC of litter was higher than from dust samples. Salmonella ranged from 50 to 1.6 million cells/gram in litter and only one dust sample had 12 cells of Salmonella. As Salmonella levels found in litter increased, the probability of obtaining a dust Salmonella positive results also increased. In experiment 2, moisture content ranged from 13, 18, 23, 28, to 33%. Litter recovery for APC, Salmonella, E. coli and coliforms counts did not differ with increasing moisture levels. Dust sample bacterial counts significantly decreased with increasing moisture levels. Results from this in vitro study indicate that there is potential for Salmonella to be present in airborne dust and that higher levels of Salmonella in litter increase the likelihood of detecting Salmonella in airborne dust. Additionally, with higher litter moisture percentage, prevalence of Salmonella in airborne dust was decreased.

Technical Abstract: Dust present in poultry houses can contain high concentrations of microorganisms and has the potential to include pathogens from the litter. The objective of this study was to examine the potential for litter to dust transfer of aerobic bacteria, Salmonella, E. coli, and coliforms, and the role of the litter moisture on this process. To evaluate litter to dust transfer of bacteria (Experiment 1), used poultry litter in flasks was inoculated with Salmonella Typhimurium from 10^2 to 10^9 CFU/mL. To evaluate the effect of litter moisture on litter to dust microbial transfer (Experiment 2), litter was inoculated with 10^9 S. Typhimurium with increasing amounts of sterilized water was added for moisture adjustment. Dust was generated by blowing air in a direct stream onto inoculated litter while simultaneously collecting dust through impingement. Following litter and dust sample collection, microbial analyses for Salmonella, E. coli, coliforms, and aerobic plate counts (APC) were conducted. Both experiments were repeated five times and their data analyzed by one-way ANOVA and simple logistic regression. In experiment 1, APC of litter (log10 CFU/g) and dust samples (log10 CFU/L) were 10.54 and 4.95, respectively. Salmonella ranged from 1.70 to 6.21 log10 CFU/g in litter and only one dust sample had 1.10 log10 CFU/L of Salmonella. As Salmonella levels found in litter increased, the probability of obtaining a dust Salmonella positive results also increased. In experiment 2, moisture content ranged from 13.0, 18.2, 23.0, 28.2, to 33.3%. Litter recovery for APC, Salmonella, E. coli and coliforms counts did not differ (P > 0.05) with increasing moisture levels. Dust sample bacterial counts significantly decreased with increasing moisture levels (P < 0.0001). Results from this in vitro study indicate that there is potential for Salmonella to be present in airborne dust and that higher levels of Salmonella in litter increase the likelihood of detecting Salmonella in airborne dust. Additionally, with higher litter moisture percentage, prevalence of Salmonella in airborne dust was decreased.