Abstract
Biocides are used without restriction for several purposes. As a consequence, large amounts of biocides are released without any control in the environment, a situation that can challenge the microbial population dynamics, including selection of antibiotic resistant bacteria. Previous work has shown that triclosan selects Stenotrophomonas maltophilia antibiotic resistant mutants overexpressing the efflux pump SmeDEF and induces expression of this pump triggering transient low-level resistance. In the present work we analyze if two other common biocides, benzalkonium chloride and hexachlorophene, trigger antibiotic resistance in S. maltophilia. Bioinformatic and biochemical methods showed that benzalkonium chloride and hexachlorophene bind the repressor of smeDEF, SmeT. Only benzalkonium chloride triggers expression of smeD and its effect in transient antibiotic resistance is minor. None of the hexachlorophene-selected mutants was antibiotic resistant. Two benzalkonium chloride resistant mutants presented reduced susceptibility to antibiotics and were impaired in growth. Metabolic profiling showed they were more proficient than their parental strain in the use of some dipeptides. We can then conclude that although bioinformatic predictions and biochemical studies suggest that both hexachlorophene and benzalkonium chloride should induce smeDEF expression leading to transient S. maltophilia resistance to antibiotics, phenotypic assays showed this not to be true. The facts that hexachlorophene resistant mutants are not antibiotic resistant and that the benzalkonium chloride resistant mutants presenting altered susceptibility to antibiotics were impaired in growth suggests that the risk for the selection (and fixation) of S. maltophilia antibiotic resistant mutants by these biocides is likely low, at least in the absence of constant selection pressure.
Highlights
Biocides constitute a group of antimicrobials used in several cleaning and general disinfection practices [1,2,3]
This biocide-mediated transient expression of the pump implies the extrusion of triclosan as well as the efflux of several antibiotics, including quinolones, erythromycin, tetracycline and chloramphenicol that are substrates of SmeDEF [46], which means that acquisition of biocide resistance mediated by transient overexpression of SmeDEF confers low-level antibiotic resistance
By using in silico and biochemical approaches, it can be predicted that the biocides hexachlorophene and benzalkonium chloride should induce transient antibiotic resistance mediated by the overexpression of SmeDEF
Summary
Biocides constitute a group of antimicrobials used in several cleaning and general disinfection practices [1,2,3]. As the consequence of these results a concern was raised on the possible effect that the wide and nonrestricted use of biocides for several purposes, as well as their release in waste-water treatment plants and in natural ecosystems may have on the selection of antibiotic resistant microorganisms [1,22,23,24]. This selection may occur at different environmental compartments, including human linked environments as hospital or homes, and natural ecosystems, which constitute the final fate of these compounds. We explore the effect that hexachlorophene and benzalkonium chloride may have on transient induction of antibiotic resistance of S. maltophilia, mediated by SmeDEF overexpression, as well as on the selection of antibiotic resistant mutants upon exposure to these biocides
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
