Effect of Environmental Conditions on Listeria monocytogenes Attachment and Biofilm Development on Food Plant Surfaces. Angie Rubi1, Ilan Arvelo2, and Marcos X. Sanchez-Plata2 1Zamorano University (SOWER Scholar), Food Agroindustry Engineering, Tegucigalpa, Honduras 2Texas Tech University, Department of Animal and Food Sciences, Lubbock, TX. Introduction Listeria monocytogenes (Lm) is a Gram positive bacterium that can cause a dangerous infection called listeriosis. This pathogen is a significant threat for contamination or recontamination of ready-to-eat foods during processing. Listeria monocytogenes is a serious foodborne pathogen that causes around 19% of the foodborne illness cases leading to death in the U.S., while its presence in food products is a major cause for food recalls nationwide. The formation of biofilms by Lm is a serious food safety concern for all the food industries, since it is capable to attach to many food-contact surfaces such as stainless steel, polystyrene and glass. Fig. 6: Growth of Listeria monocytogenes – Drop dilution technique Fig. 5: Summary table Objective The purpose of this study was to assess the effect of environmental conditions (temperature and nutrient content) on the ability of Listeria monocytogenes to attach to stainless-steel surfaces. Conditions to be performed are three temperatures 4, 21, and 37°C, and four different concentrations of nutrient availability 3, 10, 20, and 30g/L of TSB. Fig. 7: Two-way anova table Methods CONCLUSIONS A three-strain bacterial cocktail of Lm was prepared. Inoculation into stainless-steel coupons (4cm2) contained in centrifuge tubes with fresh Tryptic Soy Broth (TSB) as a source of nutrients. Incubated for 6 hours to allow for bacterial attachment. Coupons were rinsed with sterile Phosphate Buffered Saline (PBS) solution (10ml), to remove non-attached cells. Coupons were submerged in PBS for extraction of the attached cells. Extraction solutions were serially diluted into buffered peptone water (BPW) and plated on Modified Oxford Agar (MOX) for bacterial quantification. The number of attached Lm cells recovered was affected by the variables temperature and nutrient availability. Results indicate that at higher temperatures and lower nutrient availability the amount of cells attached remarkably increases (6.51 Log10cfu/cm2). Overall, the incubation temperature had a direct effect on bacterial attachment, while the effect of nutrient availability was dependent on the temperature of the S-S surface exposure. Fig. 3: Procedure of bacterial attachment Results REFERENCES Alonso A, Perry K, Regeimbal J, Regan P, Higgins D, 2017. Identification of Listeria monocytogenes determinants required for biofilm formation. PLoS One [Consulted 2018 March 02] 17(9): 12. https://doi.org/10.1371/journal.pone.0113696 FDA (Food and Drug Administration) 2012. Listeria monocytogenes. Bad Bug Book Handbook of Foodborne Pathogenic Microorganisms and Natural Toxins. [Consulted 2018 March 02] Pages 99-103 Scallan E, Hoekstra R, Angulo F, Tauxe R, Widdowson M, Roy S, Jones J, Griffin P, 2011. Foodborne illness acquired in the United States—major pathogens. Emerg Infect Dis [Consulted 2018 Jan 18] 17 (1):7-15 https://doi.org/10.3201/eid1701.091101p1 Fig. 1: Coupons submerge in different concentration of nutrients Fig. 2: Falcon tubes with TSB, PBS for rinse, PBS for extraction. Fig. 4: Box-plot graph representing the attached cells between temperatures and nutrient availability