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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #365040
Research Project: Characterization and Mitigation of Bacterial Pathogens in the Fresh Produce Production and Processing Continuum

Location: Environmental Microbial & Food Safety Laboratory

Title: Evaluation of Survival and Infectivity of Environmental Listeria monocytogenes Isolates in Tidal Brackish Irrigation Water

Author
item GARTLEY, SAMANTHA - University Of Delaware
item CRAIGHEAD, SHANI - University Of Delaware
item ANDERSON-COUGHLIN - University Of Delaware
item Sharma, Manan
item Handy, Eric
item JOERGER, ROLF - University Of Delaware
item HOOVER, DALLAS - University Of Delaware
item KNIEL, KALI - University Of Delaware

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction: Listeria monocytogenes (Lm) has been found in surface water used for irrigation of produce, but critical data gaps remain concerning Lm survival and infectivity in these environments. Purpose: To compare the survival and infectivity of Lm isolates from surface water in environmental waters collected over a growing season. Methods: Tidal brackish river water samples (TBRW) were collected and analyzed for total plate count (TPC), pH, and conductivity in summer 2018. Lm isolates (four from Mid-Atlantic surface water, one from vegetable wash water, and one from a 2011 cantaloupe outbreak) for survival in TBRW over 10 days. Isolates were individually inoculated in triplicate at 8.55±0.09 log CFU/mL into 10mL of TBRW or 1% Buffered Peptone Water (BPW), along with uninoculated TBRW controls, for 10 days at 16°C . Lm was enumerated on Brilliance Listeria Agar (BLA) on days 0, 3, 5, 7, and 10; sub-samples (1mL) were applied to HCT-8 cell-monolayers for infectivity on days 0, 7, and 10. Infection included incubation at 37°C, gentamicin sulfate treatment, and enumeration of infective cells enumerated on BLA. Statistical analysis was performed by one-way ANOVA, t-test, Tukey-Kramer, with n=6. Results: Initial populations of Lm (8.55 log CFU/mL) on day 0 remained unchanged in BPW or were reduced by up to 3.02 log CFU/mL after 10 days with slight variations by isolate. Significant decreases in viability and infectivity occurred for all isolates (p<0.0001) in TBRW compared to BPW. Survival and infectivity expressed as D-values for each isolate ranged from 3.31 to 100.06 days for survival and 2.31 to 62.59 days for infectivity in TBRW or BPW, respectively. Increased Lm survival was significantly correlated with lower TPC in TBRW samples. (p=0.0095). Significance: Lm environmental isolates were shown to survive and remain infective in TBRW, and their survival/infectivity may be affected by the quantity of other bacteria in water samples.