Abstract
Background: Antibiotic resistance in human and animal pathogens is mainly the outcome of human use of antibiotics. However, bacteria are also exposed to thousands of other antimicrobial agents. Increasingly those exposures are being investigated as co-selective agents behind the rapid rise and spread of resistance in bacterial pathogens of people and our domesticated animals. Methods: We measured the sub-lethal effects on antibiotic tolerance of the human pathogen/commensal Escherichia coli caused by exposure to three common biocide formulations based on either copper, pyrethrins, or atrazine as active ingredients. The influence of the efflux pump AcrAB-TolC was investigated using deletion strains, and the persistence of observed effects was determined. Results: Some effects were seen for all biocides, but the largest effects were observed with copper in combination with the antibiotic tetracycline. The effect was caused by both the induction of the adaptive efflux system and by chelation of the antibiotic by copper. Finally, persistence of the adaptive response was measured and found to persist for about two generations. Conclusions: Through a combination of microbe-chemical and chemical-chemical interactions, humanity may be creating micro-environments in which resistance evolution is accelerated.
Highlights
Besides antibiotics, a growing number of anthropogenic products are being found to affect antibiotic resistance in microorganisms (Heinemann & Kurenbach, 2017; Knöppel et al, 2017; Molina-González et al, 2014)
Effects of biocides on antibiotic response Minimum inhibitory concentration (MIC) was defined as the minimum concentration of agent in an agar plate at which no growth was observed after ca. 108 cfu were applied to the surface
Bacteria were cultured on LB agar supplemented with one of the three commercial formulations of biocide as well as different concentrations of selected antibiotics
Summary
A growing number of anthropogenic products are being found to affect antibiotic resistance in microorganisms (Heinemann & Kurenbach, 2017; Knöppel et al, 2017; Molina-González et al, 2014). The result is that chemicals and biocides whose effects on human health and the environment were never examined have repeatedly been responsible for episodes of disease, death, and environmental degradation” (Landrigan et al, 2018). Bacteria are exposed to thousands of other antimicrobial agents Those exposures are being investigated as co-selective agents behind the rapid rise and spread of resistance in bacterial pathogens of people and our domesticated animals. Conclusions: Through a combination of microbe-chemical and chemical-chemical interactions, humanity may be creating microenvironments in which resistance evolution is accelerated
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