Biofilms Have a New Foil

Listeria monocytogenes—a foodborne pathogen—has been found in some ready-to-eat meats. It causes serious illness in about 2,500 people each year, resulting in 500 deaths.

Though L. monocytogenes is killed by cooking or pasteurization, it can survive many chemicals used in in-plant sanitation programs. Thus, food can be contaminated during or after processing. The pathogen’s ability to grow at low temperatures may allow its growth in or on raw or improperly processed ready-to-eat foods even when they are refrigerated.

One source of contamination is work surfaces of processing plants where meat products are made. ARS microbiologist Judy Arnold at the Poultry Microbiological Safety Research Unit in Athens, Georgia, has been looking for improved methods to control biofilms containing L. monocytogenes. Any method needs to be acceptable to the U.S. Environmental Protection Agency.

Biofilms are protective layers of proteins and polysaccharides that surround bacteria and stick to equipment surfaces. “These protective shields trap spoilage bacteria and other pathogens that contaminate food during processing, and they resist cleaning and sanitizing,” says Arnold. “Today’s longer production runs provide more opportunity for biofilms to establish themselves, and today’s longer shelf life adds to the risk of biological contamination.”

In collaboration with Sterilex Corporation of Owings Mills, Maryland, Arnold has tested a proprietary formulation—based on alkaline peroxide and phase-transfer chemistry—that appears to be a cost-effective disinfectant for use in environments for poultry and meat production and processing. The formulation uses multiple chemical and physical actions to penetrate a biofilm, kill the microorganisms, and remove the biofilm from surfaces. It was tested against multiple disinfectants for killing and removal of L. monocytogenes biofilm.

“Results showed that the formulation was 100 percent effective, providing total kill and more than 90 percent biofilm removal,” says Arnold. “This disinfectant is more effective than currently used disinfectants in reducing L. monocytogenes biofilm growth, thus minimizing the risk of pathogenic contamination. Test evaluations also resulted in instructions for use that will meet USDA ‘zero tolerance’ regulations for L. monocytogenes.”—By Sharon Durham, Agricultural Research Service Information Staff.

Judy Arnold is in the USDA-ARS Poultry Microbiological Safety Research Unit, Richard B. Russell Research Center, 950 College Station Rd., Athens, GA 30605; phone (706) 546-3515, fax (706) 546-3068.

"Biofilms Have a New Foil" was published in the October 2009 issue of Agricultural Research magazine.