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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL ECOLOGY AND SAFETY OF FRESH PRODUCE

Location: Environmental Microbial and Food Safety Laboratory

Title: Survival of Salmonella in manure dust on spinach leaves

Authors
item Oni, Ruth -
item Sharma, Manan
item Micalef, Shirley -
item Buchanan, Robert -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 22, 2013
Publication Date: N/A

Technical Abstract: Introduction: Microbiological safety of fresh produce has attracted a lot of attention in the past three decades due to pathogen contamination along the farm to fork continuum resulting in outbreaks. Although animal manure has been identified as a major pre-harvest pathogen source, there is little research on the potential role of airborne manure dust as a vehicle for pathogen transmission. Purpose: This study assessed the survival capabilities of Salmonella in dry turkey manure particles (of a size capable of being airborne) when present on spinach leaves, as well as effect of UV radiation on that survival. Method: Turkey manure dust (125 µm) at 5% moisture level inoculated with a cocktail of Salmonella was lightly dusted onto spinach leaves under growth chamber conditions and survival monitored over 21 days. Effect of UV light on survival was factored into the experimental design such that the abaxial and adaxial sides of the leaves were compared for Salmonella survival. Treatment controls consisted of plants grown under a UV filter. Results were compared with trials where plants were inoculated with Salmonella via aerosol spray. Survival curves were generated and transformed data analyzed using SAS. Results: Under UV light, particulate manure dust significantly (P < 0.05) reduced inactivation of Salmonella on spinach leaves. Site of deposition on leaves also influenced survival as Salmonella survived preferentially (P < 0.05) on the abaxial surface. By day 7 post-inoculation, Salmonella cells in manure dust on leaves had achieved only a 2 log reduction, while population in control samples had declined by approximately 5 logs. By day 14, recovery of viable Salmonella from the abaxial and adaxial leaf surfaces was 33% (n=6) versus 0% respectively on XLD agar. Significance: This research supports the hypothesis that dust generated from poultry manure increases the likelihood that Salmonella can persist on leafy green surfaces, especially in arid areas where unintended aerosolization could frequently occur.

Last Modified: 9/23/2014
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