Skip to main content
ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #337423

Research Project: Characterization and Mitigation of Bacterial Pathogens in the Fresh Produce Production and Processing Continuum

Location: Environmental Microbial & Food Safety Laboratory

Title: Practices and conditions which promote persistence of Listeria monocytogenes on equipment surfaces and transfer to cantaloupes in the packing environment

item NYARKO, ESMOND - University Of Delaware
item KNIEL, KALIMIA - University Of Delaware
item Zhou, Bin
item East, Cheryl - Roberts
item Handy, Eric
item Luo, Yaguang - Sunny
item Millner, Patricia
item Sharma, Manan

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction: Investigation of the 2011 U.S. listeriosis outbreak associated withcontaminated cantaloupes revealed that transfer of L. monocytogenes(Lm) from equipment surfaces to melons in the packing facility was a potential route of contamination. Purpose:This study examined the persistence of Lm on soiled material, different types ofsurfaces,andtransfer to cantaloupes in a simulated-packing environment. Methods:Clean andunclean(0.5mL cantaloupe extract; dried 6h) surfaces of nylon-brushbristles (1g),and 16 cm2 of conveyor belt-material(polyvinyl-chloride, polyurethane, and nitrile-rubber),and foam-pads (16cm2)were prepared. Each surface received a multi-strain inoculum ofLm(4.5-log10CFU/mL), and was subsequentlystored at 25°C. Lmpopulations from surfaceswere recovered for up to 15days. Aseparate set of inoculated uncleansurfaces received water (1mL) 24h prior to eachtime of enumeration. Conveyor-beltand foam-pad materials were spot-inoculated (50µL; 2.5-log10CFU/surface),and 15 consecutive wet melons were manually rolled over each spot. Melons were tested forpresence/absence of Lm. Results: Lmpopulationsdecreased from 4.5 on day0 to below the detection limit, 2.3±0.5, and 3.1±0.2log10CFU/surface on clean conveyor belts, brush, and foam-pad materials, respectively, by day10. Lmwas still present on clean surfaces after 21 days.On unclean surfaces, Lmpopulations remained unchanged (4.5log10CFU/surface) from days0to 14. Multivariate ANOVA revealed that unclean materialsignificantly (p<0.05) promoted persistence of Lm compared to clean surfaces.Comparison of Lmpersistence was significantly different on various surfaces: foam-pad>brush>polyurethane>polyvinyl-chloride, rubber-nitrite.An ANOVA of probability distributions of contaminated melons (n=90 melons per surface) revealed that foam-pad contaminatedsignificantly (p<0.05) more melons (78±5%) than polyvinyl-chloride (55±11%) = polyurethane (47±9%) =nitrile-rubber (33±10%) belts. There was no correlation between thepresenceof L. monocytogeneson melons and the order in which they were exposed to contaminated surfaces. Significance:Unclean surfaces and wet surfaces promote persistence of Lm and led towidespread contamination of melons.