Food plant managers have been cautioned that washing down floor drains with high-pressure equipment could make it easier for Listeria monocytogenes to transfer from the outlet back onto the processing line.
The study by researchers from the Food Safety Consortium at Kansas State University said their previous work had already established that open floor drains in processing facilities can harbour bacteria.
But latest research has found that 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”, said study author Jasdeep Saini.
The researchers also noted the potential hazard could be remedied if workers were changed the way they cleaned.
“The situation can be remedied, but workers need to be trained how to do so,” said Saini
The research team conducted tests to determine the potential for translocation of the Lysteria bacteria from drains to food contact surfaces. Stainless steel markers were placed at heights of one, three and five metres above drain level. A high-pressure hose was used to clean the drains and researchers checked the markers and took samples after eight hours and then at 48 hours.
The results for both sets of tests confirmed that cells from the drain were found at all three height levels, with the highest reading found on the one-foot marker, said a KSU statement. The team also discovered the presence of bacterial cells had increased after 48 hours. The likely cause for this was because of the longer time available for the “cells to proliferate and form a biofilm – thin resistant layers of microorganisms – as protection against environmental stress”, said the researchers.
“Listeria has been known to form bioflilms,” added Saini. “Biofilms develop between 36 and 48 hours. If there are biofilms existing in the drain, how those are actually translocated can cause contamination on the line.”