Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2024
Publication Date: 6/13/2024
Citation: Prabhukhot, G., Eggelton, C., Vinyard, B.T., Patel, J.R. 2024. Novel Bio-inline® reactor to evaluate sanitizer efficacy in removing multispecies biofilms formed by Escherichia coli O157:H7 and Listeria monocytogenes. Journal of Food Protection. 10: e100314. https://doi.org/10.1016/j.jfp.2024.100314.
DOI: https://doi.org/10.1016/j.jfp.2024.100314

Interpretive Summary: Contamination of food with bacterial pathogens may occur during a complex farm-to-fork product chain. Bacterial pathogens may attach to equipment surfaces, form biofilm on surface, and further contaminate food during processing. We evaluated a novel bio-reactor for multi-species E. coli O157:H7 and L. monocytogenes biofilm removal from equipment surfaces with chlorine. A 500-ppm chlorine treatment for 1 or 4 min significantly removed multispecies E. coli O157:H7 biofilms from stainless steel and PTFE surfaces, grown at 2.462 N/m2 shear stress. The shear stress used in the biofilm formation influenced the most in multispecies L. monocytogenes biofilm removal by chlorine. In general, the biofilm removal by chlorine was superior on stainless steel surface whereas additional interventions may be required to remove biofilm from EPDM rubber surface. Food processors can use the information in selection of equipment surfaces and adequate interventions to prevent food contamination by pathogens in biofilm.

Technical Abstract: The efficacy of sanitizer in multispecies biofilm removal may be influenced by a combination of factors such as sanitizer exposure, bacterial species, surface topographies and shear stresses. We employed a novel In-line bioreactor to investigate the interactions of these variables on biofilm removal with chlorine. CDC bioreactor was used to grow E. coli O157:H7 and L. monocytogenes biofilms as a single species or with R. insidiosa as a multispecies biofilm on stainless steel (SS 316L), PTFE and EPDM coupons at shear stresses 0.368 and 2.462 N/m2 for 48-hours. Coupons were retrieved from CDC bioreactor and placed in In-line bioreactor; and 100, 200 or 500 ppm of chlorine was supplied for 1-and-4 minutes at a flow rate of 1.2 Liter per min. Bacterial populations in biofilms were quantified pre- and post-treatment by spiral plating on selective media. After chlorine treatment, reduction (Log CFU/cm2) in pathogen populations obtained from three replicated were analyzed for statistical significance. A 1-min chlorine treatment (500 ppm) on multispecies E. coli O157:H7 biofilms grown at high shear stress of 2.462 N/m2 resulted in significant E. coli O157:H7 reductions on SS 316L (2.79 log CFU/cm2) and PTFE (1.76 log CFU/cm2) compared to EPDM (0.92 log CFU/cm2) surfaces. Similar trend was also observed for biofilm removal after a 4-min chlorine treatment. Single species E. coli O157:H7 biofilms exhibited higher resistance to chlorine when biofilms were developed at high shear. The effect of chlorine in L. monocytogenes removal from multi-species biofilms was dependent primarily on the shear stress at which they were formed than surface topography of materials. The removal of E. coli O157:H7 biofilms from EPDM material may require critical interventions due to difficulty in removing this pathogen from biofilms. Besides surface topography, shear stresses at which biofilms formed does influence the effect of sanitizer.