Progress 10/01/11 to 09/30/12
Outputs
Progress Report Objectives (from AD-416): To investigate the mechnisms of how the interactions among various Salmonella and STEC serotypes would affect biofilm formation on different solid surfaces, and to analyze the resistance of the single- or multi- species biofilms to various sanitizing reagents commonly used in the meat processing plants. Approach (from AD-416): We will test the effects of co-inoculation of Salmonella, STEC O157:H7, and non-O157 strains on biofilm formation. These tests will be performed on materials commonly used in the meat industry, such as stainless steel and plastic. We will further test biofilm formation on solid surfaces with preformed biofilms by different species, which mimics a likely event in commercial production. To study the effect of bacterial coexistence on biofilm resistance to sanitation, sanitizers commonly used in meat processing plants, including VanquishTM, chlorine, and hydrogen peroxide, etc., will be tested to compare their effectiveness against single- or multi-species biofilms. The effects of sanitizers alone and after hot-water pressure washing will be determined to mimic in-plant sanitizing conditions. Various Shiga-toxigenic E. coli (STEC) and Salmonella serotypes are capable of forming biofilms on food contact surfaces, and biofilm cells are usually more resistant to sanitizing agents than free-flowing cells of the same species. Therefore, biofilm formation is a serious food safety concern. In nature, bacteria can form single � species biofilms, or more frequently coexist in multispecies communities and form mixed biofilms. We evaluated the potency of biofilm formation by various STEC and Salmonella serotypes on materials commonly used in the meat industry, including plastic, PVC, and stainless steel. We also investigated how coexistence of STEC O157:H7 and the non-O157 serotypes, as well as Salmonella Typhimurium strains would affect bacterial single species growth competition and mixed biofilm composition. Furthermore, we tested how mixed biofilm formation would affect bacterial resistance to common sanitizers. Our results demonstrated that STEC and Salmonella biofilm formation could be affected by a combination of bacterial physiological and environmental factors, including bacterial strain and serotype, surface materials, and temperature, etc. Our sanitization study demonstrated that sanitizer resistance of S. Typhimurium and STEC biofilms was highly dependent upon the expression of various cell components. The results highlight the potential risk of cross- contamination by multispecies biofilms in food safety and calls for increased attention to proper sanitization practice in food processing facilities.
Impacts
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Publications
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