Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/11/2011
Publication Date: 7/31/2011
Citation: Wang, B.M., Annous, B.A., Nivens, D.E. 2011. Survival of Escherichia coli 0157:H7 in topographical features on stainless steel surfaces from gas and liquid phase chemical treatments. IAFP Annual Meeting, Milwaukee, Wisconcin, July 31-August 3, 2011.,Volume 1, P.1. Interpretive Summary:
Technical Abstract: To identify microenvironments that harbor and potentially protect pathogens from intervention strategies and in turn become a source of microbial recontamination. Examining factors such as fluid dynamics and topographical features which form microenvironments and promote pathogen survival will allow for improved treatments to effectively eliminate pathogens and thus reduce the risk of recontamination. This study evaluated the effect of microenvironments on stainless steel surfaces on the efficacy of antimicrobial agents for treating biofilms. Eight hour E. coli O157:H7 biofilms formed on stainless steel test surfaces with and without fabricated grooves (<100-500 µm wide and 100-750 µm deep) using a flow-through system were treated with antimicrobial agents hypochlorite (20-2000 ppm) and chlorine dioxide (0.7-2.2 mg l-1) for 5-30 min. An isolation system was developed for two growth-based assays, recovery and regrowth, to determine efficacy of treatment. COMSOL Multiphysics was used to model flow and diffusion of antimicrobial agents in tested microenvironments. Results indicated that deeper grooves afforded cells more protection against antimicrobial agents. Although the recovery assay showed 200 ppm hypochlorite for 5 min led to a 6 log reduction on all surfaces, the regrowth assay indicated 30% of the samples survived treatment at deeper grooves. Diffusion models showed that 10 min was needed for maximum treatment concentration to reach the bottom of the deeper grooves. Treatment with chlorine dioxide gas at 0.7 mg l-1 (236 ppm) for 10 min also was not successful in eradicating the biofilm; however, chlorine dioxide concentration of 2.2 mg l-1 (741 ppm) for 5 min eliminated regrowth. Microenvironments of narrower grooves have been fabricated and are currently being tested. Our findings will identify problematic scenarios (where pathogens are most difficult to kill) that should be evaluated when optimizing treatment regiments to effectively eliminate pathogens on food contact surfaces.