P3-61 Transfer of Microorganisms from a Dairy Calf Operation to an Adjacent Pistachio Orchard

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Christopher Theofel , University of California-Davis , Davis , CA
Thomas Williams , University of California-Davis , Davis , CA
Eduardo Gutierrez , North Carolina State University , Raleigh , NC
Gordon Davidson , U.S. Food and Drug Administration , College Park , MD
Michele Jay-Russell , University of California-Davis, Western Center for Food Safety , Davis , CA
Linda J. Harris , University of California-Davis , Davis , CA
Introduction:  In recent surveys, Salmonella has been isolated from raw unprocessed pistachios at a prevalence of about 0.60%. Sources of Salmonella in pistachios are not well understood including the potential for contamination in the orchard prior to or during harvest.

Purpose:  To evaluate transfer of microorganisms from a livestock operation to an adjacent pistachio orchard.

Methods:  Orchard surface (drag swab), air (microbiological air sampling device), soil, and dust (pistachio leaf surface) samples were collected in an orchard adjacent (<20 m distance) to a commercial dairy calf operation (livestock orchard) and a single control orchard (surrounded by other pistachio orchards) over a two-year period. Air and cattle manure samples were collected within the livestock operation. Dry solids rinsed from leaf surfaces, aerobic plate count, presence of Salmonella and Escherichia coli,and bacterial community analysis through 16S rRNA sequencing were determined.

Results:  Salmonella was isolated from manure and from 4 of 63 drag swabs collected from within the livestock orchard, but not from drag swabs collected within the control orchard (0 of 12). Salmonella was not detected in air or soil samples collected within the orchards (0 of 303). E. coli was isolated from 25 of 45 (56%) and 1 of 18 (5.6%) soil samples in the livestock and control orchards, respectively. Escherichia coli was isolated from 46 of 198 (23%) and 1 of 36 (2.8%) air samples in the livestock and control orchards, respectively. Members of the Corynebacteriaceae family, often associated with animals and the most prevalent bacterial family present in manure samples taken within the livestock operation, were, on average, more abundant (21%) in the phyllosphere of trees in the livestock orchard than in the control orchard (5.8%).

Significance:  Livestock-associated microorganisms from animal operations may transfer into adjacent orchards; the food safety implication of this movement is unknown.