Determination of Potential Contribution of Biofilm Formation and Sanitizer Resistance to Beef Product Contamination by Salmonella Enterica

<p>Salmonella enterica are a diverse group of foodborne pathogens with over 2, 500 serotypes identified. However, only 20 Salmonella serotypes account for more than 70% of human salmonellosis cases, which are mainly associated with the consumption of contaminated foods including red meat. Surveys of retail and commercial ground beef samples show that certain Salmonella serotypes or strains are more frequently observed in meat contamination at commercial plants. Currently, the precise mechanism and pathogen source responsible for Salmonella contamination in commercial establishments remains unknown. Biofilm formation is an important strategy that helps bacteria survive under adverse circumstances. Biofilm cells are much more resistant to sanitization than planktonic cells of the same species, so it is difficult to completely inactivate biofilms formed on food contact surfaces and in the environment. Biofilms can serve as a cross-contamination source when detached from the surfaces. Thus, one logical explanation for meat contamination by foodborne pathogens could be that certain in-plant colonized bacterial strains, including Salmonella enterica, are better able to survive the exposure to sanitizers, likely through biofilm formation. When the surviving bacteria in mature biofilms, which are unevenly distributed on contact surfaces, become detached as the meat products pass over the area, random occasions of meat contamination could occur. These occasions would exhibit no apparent temporal/spatial patterns or association with any process control failure. To test our hypothesis, we propose a series of comparative studies using two groups of Salmonella strains. Group A is a reference collection of 48 Salmonella enterica isolates commonly associated with cattle, beef or clinically infected humans, including 12 strains each from serotypes Anatum, Montevideo, Newport, and Typhimurium. Group B includes Salmonella enterica strains isolated from contaminated beef products at commercial plants in the U.S., ideally including strains isolated from multiple incidences and from multiple trim lots harvested at various time points that could represent the breadth of Salmonella strains/serotypes causing meat contamination in the current industrial settings.</p>

<p>Comparative studies will include:

<ol><li> Biofilm formation on contact surfaces of materials commonly used in the meat industry;
<li>Minimal inhibitory concentrations of common sanitizers;</li>
<li>Biofilm cell survival and recovery growth after sanitization;</li>
<li>The efficiency of biofilm cell transfer from contact surface to meat products;</li>
<li>Molecular genomic typing of the Salmonella isolates to gain information regarding the source of contamination, specifically whether contamination is derived from a single point source or from multiple sources. Genetic typing of the strains also would provide information regarding where in the process (slaughter floor vs. fabrication) contamination might occur and if any particular strains/serotypes with specific genomic patterns are more commonly associated with contamination incidences.</li></ol></p>