Biocides used at sub-lethal doses in the food industry, with the goal of enhancing hygiene and food safety, may be having precisely the opposite effect—instead increasing pathogens’ resistance to antibiotics and promoting their ability to form biofilms (a major virulence factor for human infections), according to new research from Spanish scientists.
Rosa Capita, of the Department of Food Hygiene and Food Technology at the University of Leon in Spain, and colleagues explored what happened when E. coli bacteria are exposed to sub-lethal doses of three food-grade biocides. Exposure to two of the three biocides led to increased resistance against 14 of 29 antibiotics tested, as well as to the biocides themselves. By contrast, sub-lethal exposure to biocide trisodium phosphate actually reduced E. coli’s ability to form biofilms, and boosted resistance only to a single antibiotic.
“The presence of biofilms on food-processing surfaces favors the contamination of foodstuffs,” explains Capita, who notes that this study was the first to measure the ability of E. coli to form biofilms after exposure to the three biocides tested.
“These findings are in agreement with reports of other authors, where adaptation of E. coli to both chemical and physical sub-lethal stresses has been demonstrated,” the researchers observe. “The increased tolerance observed suggests that the use in food environments of compounds which when used inappropriately may provide sub-lethal exposure represents a real risk for the development of adaptation to biocides.”
The study appeared online ahead of print in the journal Applied and Environmental Microbiology, and will be published in the February 2014 edition of the journal.