January 10, 2014
1 min read

Improper use of biocides may increase antimicrobial resistance

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Use of sub-lethal concentrations of biocides increased antibiotic resistance in Escherichia coli and enhanced the bacteria’s ability to form biofilm, according to new study data.

“Biofilm formation is considered an important virulence factor in human infections, and it has been reported that approximately 80% of all bacterial infections are associated with biofilms,” researchers wrote in Applied and Environmental Microbiology.

In the study, five colonies of E. coli were subjected to various concentrations of three biocides widely used in the food industry: trisodium phosphate, sodium nitrate and sodium hypochlorite. The researchers studied the bacteria’s ability to adapt to sub-lethal doses of the compounds, if exposure to the specific biocides influenced the formation and architecture of biofilm, and the development antimicrobial resistance as a result of the exposure. Unexposed cultures were used as controls.

According to the researchers, the cultures “exhibited an acquired tolerance to biocides” after being exposed to the compounds. Moreover, adapting to the biocides — with the exception of trisodium phosphate — influenced the bacteria to produce biofilm, which increased both in volume and surface coverage.

Cultures exposed to biocides also demonstrated increased resistance to a range of antibiotics, including aminoglycosides, cephalosporins and quinolones, compared with negative controls. Exposure to sodium nitrate led to the greatest antimicrobial resistance in E. coli (P<.05), boosting resistance to 14 of 29 antibiotics tested. Bacteria subjected to sodium hypochlorite became resistant to three antibiotics and exposure to trisodium phosphate increased resistance to just one antibiotic.

“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 wrote. “The increased tolerance observed suggests that the use in food environments of compounds which, when used inappropriately (improper use, inappropriate storage or excessive amounts of organic matter, known to inactivate several biocides) may provide sub-lethal exposure, represents a real risk for the development of adaptation to biocides.”

Disclosure: The researchers report no relevant financial disclosures.