Survival of Salmonella enterica in Dried Turkey Manure

Introduction:  The enteric pathogen Salmonella enterica has been associated with foodborne outbreaks involving leafy greens. While identified as a risk factor, there have been few studies examining the role airborne transmission could play in the contamination of leafy greens. The dust associated with the application of dried poultry manure can become airborne and spread fecal contamination within fields in areas where poultry facilities are interspersed with fresh produce farms. As a first step to assessing this potential source of contamination, it is necessary to assess the likely survival of S. enterica in poultry manure particles of a size capable of being airborne.

Purpose:  The objective of this study was to investigate the survival capabilities of two serovars of S. enterica Typhimurium and Enteritidis, in turkey manure dust at different moisture levels.

Methods:  Fresh turkey manure (fecal material plus bedding) was dehydrated to <5% moisture content and processed until ‘dust’ particle sizes of approximately 125 µm were obtained. The ‘dust’ was sterilely rehydrated to three moisture levels - 5%, 10% and 15%, and inoculated with a cocktail of S. Typhimurium and S. Enteritidis at target levels of 10⁶ CFU/ml. Salmonella spp. survival at each moisture level was monitored over 60 days using viable plate count methods on BHI, XLD and VRBG agars. Survival curves were plotted and basic extrapolation done.

Results:  Significant (P < 0.05) differences were observed in the inactivation rates of Salmonella spp. based on moisture levels−lowest moisture level of 5% corresponded to slowest inactivation rate. Manure dust with moisture levels 5%, 10%, and 15% had, respectively, achieved log reductions of 1.75, 2.96 and 3.06 on XLD agar by day 14, and enrichments indicated survival beyond day 60 for all moisture levels.

Significance:  Data obtained from this study suggest that pathogenic Salmonella spp. cells can for survive for extended periods when present on manure dust particles.