Quantification and Comparison of Salmonella Typhimurium and Heidelberg Biofilm Formation on Plastic Coupons

Introduction:  Plastic containers that are used to transport and store food products are subject to biofilm formation once exposed to microorganisms. Biofilms can survive harsh environmental conditions, and once established, these bacterial communities can result in widespread contamination, which will ultimately lead to foodborne illness.

Purpose: The purpose of this study was to quantify and compare Salmonella Typhimurium and Heidelberg biofilm formation on plastic coupons by conventional microbiological methods.

Methods:  Salmonella Typhimurium and Heidelberg were inoculated into separate 40 ml sterile specimen cups containing enrichment broth and plastic coupons, and the cups were incubated for 24 h at 37°C, 110 rpm. Subsamples (obtained at 0, 4, 8, 12, and 24 h) were diluted and plated in duplicate to determine the CFU/ml of unattached cells, and following 24 h of growth, coupons were rinsed with deionized water and vigorously vortexed for 1 min with 3 g of glass beads and 20 ml of phosphate buffer saline (pH 7.4) to remove attached cells.

Results: The percent CFU/ml recovered (biofilm concentration/starting concentration) from the plastic coupons for Salmonella Typhimurium and Heidelberg was (0.09 ± 0.01%) and (0.06 ± 0.15%), respectively.

Significance:  This research provides useful information regarding biofilm formation on plastic, and will ultimately educate food producers that consider reusing plastic containers for the transportation and storage of food products, especially fresh produce.