The use of biocides in food products may be endangering, rather than protecting, public health by increasing antibiotic resistance in potentially harmful bacteria, warn researchers.
The study reveals that exposing Escherichia coli (E. Coli) bacteria to sub-lethal concentrations of each of three food-grade biocides could result in greater antibiotic resistance, a greater ability to form damaging and potentially virulent biofilms and to survive normally lethal doses of biocides.
Writing in the journal Applied and Environmental Microbiology, the team behind the research suggests that the biocides trisodium phosphate (TSP), sodium nitrite (SNI) and sodium hypochlorite (SHY) could represent a public health risk when used at 'improper' levels such as sub-inhibitory or sub-lethal concentrations.
"Recent scientific evidence suggests that the selective pressure exerted by the use of biocides at sub-lethal concentrations could contribute to the expression and dissemination of antibiotic resistance mechanisms," explained the researchers - led by Rosa Capita from the University of Leon, Spain.
The team found exposures to the biocide sodium nitrite increased resistance to 14 out of 29 antibiotics tested.
E. coli also acquired tolerance to the biocides, especially sodium nitrite and sodium hypochlorite, and the two biocides were also found to improve the microbes' ability to form protective biofilms that can boost the risk of food contamination by providing a reservoir of microorganisms.
Conversely, exposure to the biocide trisodium phosphate reduced E. coli's ability to form biofilms, and boosted resistance only to a single antibiotic, the team found.
"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," said Capita and her colleagues.
"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."