Common Cleaning Process Helps Breed Listeria

FAYETTEVILLE, Ark.New research suggests that food-processing plants that wash floor drains to clear out pathogenic bacteria may be making it easier for Listeria monocytogenes to travel from the drain to points on the processing line.

Food Safety Consortium researchers at Kansas State University found that the aerosols generated by the washing can transfer the bacterial cells away from the drain as intended but onto surfaces where food is being processed a few feet above the floor.

Researchers ran tests to find out the potential for translocating L. monocytogenes from drains to food contact surfaces. They placed stainless steel markers at heights of one, three and five feet above the drain level and checked the markers after using a high-pressure hose to wash the drain and took samples after eight hours and again after 48 hours.

The numbers for both the eight-hour and 48-hour tests showed that bacterial cells from the drain were found at all three height levels, the highest number at the 1-foot level closest to the drain. More bacterial cells were present on the contact surfaces after 48 hours than after eight hours, likely because of the longer time available for the cells to proliferate and form a biofilm as protection against environmental stress.