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Mechanisms of Chemical Inactivation of Pathogenic Bacteria on Food and Food Contact Surfaces


The goal of this project is to control food borne pathogens by improving food contact surface and tissue decontamination processes. Objectives are: <OL> <LI> Evaluate the chemical inactivation of Salmonella typhimurium DT104, Campylobacter, and Arcobacter butzleri contained in multispecies biofilms on nonporous surfaces <LI>Develop methods for the direct observation of foodborne pathogens on plant and animal tissue<LI> Determine the mechanisms by which Salmonella, E. coli O157:H7 and Listeria monocytogens present on the surface of plant and animal tissues survive attempted disinfection.

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APPROACH: Biofilm model systems will be developed using environmental microflora. Selected pathogens will be introduced into the biofilm and their behavior determined. Pathogen-containing biofilms will be treated with chemical sanitizing agents and the survival of pathogens determined. Pathogens of the surfaces of plant and animal tissues (lettuce, apples, tomatoes, broccoli, and chicken skin) will be observed using confocal scanning laser microscopy to determine penetration of the cells into the tissue. Viability stains and cell elongation will be used for direct microscopic observation of cell viability. The impact of these treatments on pathogen viability at specific tissue microlocations after decontamination will be determined.
PROGRESS: 1999/01 TO 2004/12<BR>
A statistical model was developed to predict the inactivation of Listeria monocytogenes in biofilms subject to heat treatment. This model will allow food processors to estimate the probability that Listeria will survive any time temperature combination between 70 and 80 C. Separate models for biofilms on rubber and stainless steel were developed. The model also compensates for the presence of food soils and spoilage bacteria on the surface. In other research, we determined the behavior of Listeria monocytogens on surfaces covered with condensate. When listeria is in biofilms on condensate-covered surfaces it survived for over 35 days at 12 C with no nutrient additions. Significant numbers of listeria were released from the surface into the condensate over this time. Research on E. coli O157:H7 demonstrated that capsule production was associated with attachment of the pathogen to apple and lettuce. Capsule production had a greater influence on attachment than electrostatic charge.
IMPACT: 1999/01 TO 2004/12<BR>
Processors of ready-to-eat foods must take steps to ensure the control of Listeria monocytogenes in the processing environment. This research provides verification that control can be achieved through proper application of cleaning and sanitizing chemicals. This information will be used in the development of standard sanitary operating procedures as a prerequisite for HACCP program success.

Frank, Joseph
University of Georgia
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