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Mechanisms of Escherichia coli O157:H7 Attachment To and Transfer Between Meat and Equipment Surfaces


The ability of pathogenic bacteria to attach to food and equipment surfaces is a safety concern to
the food industry. There is a limited amount of research examining E. coli O157:H7’s
mechanisms in attaching to beef tissues and/or food equipment surfaces. Previous work
conducted by one of the investigators in this project focused on Listeria monocytogenes
attachment to ready-to-eat meat and poultry products and food equipment surfaces. The research
demonstrated that transfer of bacteria was significant between equipment and meat surfaces. <P>
The overarching goal of this project was to generate basic information about the mechanisms of
attachment of Escherichia coli O157:H7 to meat and processing equipment, as well as the
transfer between the two environments. A better understanding of these attachment mechanisms
will enable the development of practical and effective intervention strategies that can be applied
in industry to prevent the contamination of meat and equipment surfaces. <P>
Specifically, the researchers sought to research the attachment of E. coli O157:H7 to meat
surfaces and two materials commonly found in equipment in beef processing facilities. The
researchers also examined the transfer of bacteria from contaminated beef to non-contaminated
surfaces, and from contaminated surfaces to non-contaminated beef. Fat versus lean tissue type’s
effect on bacterial transfer between meat and equipment surfaces was also examined.

More information

Findings: Transfer of E. coli O157:117 persisted beyond 21 contacts when the original surface (beef or equipment: high density polyethylene or stainless steel) was heavily contaminated (i.e. high inoculum = ~106 Log CFU/cm2) and beyond 15 contacts when less contaminated (i.e. low inoculum = ~103 Log CFU/cm2). Although there were differences (P<0.001) in surface roughness between 11DPE and SS, contact surface had a smaller effect (P=0.0014) on bacterial transfer than inoculum level (P<0.0001), meat type (lean or fat) (P<0.0001) and number of contacts (P<0.0001). Overall, bacterial numbers decreased to <1000 cells as the number of contacts increased to 21 in high inoculum trials or 15 in low inoculum experiments. A mathematical model could predict transfer of E. coli O157:117 between beef and equipment surfaces (0.46 &#8804; R2 &#8804; 0.92). Visualization of bacterial cells on meat surfaces using confocal laser scanning microscopy and subsequent confirmation using computer software showed cells had a preferential allocation in the spaces between the muscle fibers. Results suggest that, in spite of SS and 11DPE being common equipment materials used in meat manufacturing facilities, because of their surface roughness, they may contribute to bacterial transfer when either meat or equipment surfaces are contaminated. <P> For complete projects details, view the <a href="…; target="_blank">Project Summary. </a>

Ryser, Elliot
Michigan State University
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