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P3-224 Evaluation of Listeria monocytogenes Survival and Infectivity in Non-traditional Agricultural Waters

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Samantha Gartley , University of Delaware , Newark , DE
Adam Vanore , University of Delaware , Newark , DE
Shani Craighead , University of Delaware , Newark , DE
Manan Sharma , USDA ARS Environmental Microbial and Food Safety Laboratory , Beltsville , MD
Kalmia Kniel , University of Delaware , Newark , DE
Introduction: Listeria monocytogenes (Lm) is an enteric bacterium that can be found in environmental reservoirs. Restricted water availability for agriculture has increased interest in surface and reuse water sources which could potentially transmit Lm.

Purpose: Persistence and infectivity of Lm recovered from brackish tidal (TW) and vegetable wash water (VW) were compared.

Methods: Water was collected from the Mid-Atlantic region at two sites in Fall 2016. Lm (environmental isolate from 2011 outbreak associated with cantaloupes) was inoculated into 10ml of collected water at 8.62 log CFU/ml, all in triplicate, which was held for ten days at 16°C to mimic irrigation water temperatures during harvest. Lm was recovered on Brilliance Listeria Agar (BLA) on days 0, 3, 5, 7, and 10. Cell culture infectivity with recovered Lm from day 7 was performed by inoculating 1ml of sample onto human ileocecal monolayers (HCT-8) for 30 min, washing with HBSS, treating with 10µg/mL gentamicin sulfate for 30 min, and incubating at 37°C for one hour after which infective Lm cells were recovered and enumerated on BLA. Statistical analysis was performed by one-way ANOVA and t-test.

Results: Initial populations of Lm were 8.62±0.32 log CFU/ml on day 0 across water types.  By day 7, Lm populations had significantly (p < 0.05) declined to 6.44±0.41 log CFU/ml in VW while Lm populations in TW remained at 8.33 ±0.16 log CFU/ml at day 7. Infectivity assay data for day 7 samples showed recovery of 5.06±0.32 log CFU, 3.97±0.36 log CFU, and 3.36±0.95 log CFU from BPW, VW, and TW, respectively, from infected HCT-8 cells, the inverse of the total day 7 counts for the VW and TW samples.

Significance: Lm inoculated into brackish tidal and vegetable wash waters showed decreased viability and decreased infectivity as demonstrated in a cell culture assay.

Back to: Poster Session 3 – Low-water Activity Foods, Packaging, Produce, Microbial Food Spoilage, Antimicrobials, Laboratory and Detection Methods, Water
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