title: Resistance Mutations in gyrA and parC are Common in Escherichia Communities of both Fluoroquinolone-Polluted and Uncontaminated Aquatic Environments.
abstract: Alterations in the target proteins of fluoroquinolones, especially in GyrA and ParC, are known to cause resistance. Here, we investigated environmental Escherichia communities to explore the possible link between the abundance of mutations, and the exposure to fluoroquinolones. Sediment samples were collected from a relatively pristine lake, up and downstream from a sewage treatment plant, and from several industrially polluted sites. The quinolone resistance-determining regions of gyrA and parC were analyzed using amplicon sequencing of metagenomic DNA. Five non-synonymous substitutions were present in all samples, and all of these mutations have been previously linked to fluoroquinolone resistance in Escherichia coli. In GyrA, substitutions S83L and D87N were on average detected at frequencies of 86 and 32%, respectively, and 31% of all amplicons encoded both substitutions. In ParC, substitutions S80I, E84G, and E84V were detected in 42, 0.9, and 6.0% of the amplicons, respectively, and 6.5% encoded double substitutions. There was no significant correlation between the level of fluoroquinolone pollution and the relative abundance of resistance mutations, with the exception of the most polluted site, which showed the highest abundance of said substitutions in both genes. Our results demonstrate that resistance mutations can be common in environmental Escherichia, even in the absence of a fluoroquinolone selective pressure.
authors.affiliation: Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg Gothenburg, Sweden ; Department of Mathematical Sciences, Chalmers University of Technology Gothenburg, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Johnning
authors.affiliation: Department of Mathematical Sciences, Chalmers University of Technology Gothenburg, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Kristiansson
authors.affiliation: Department of Chemistry, Umeå University Umeå, Sweden.
authors.forename: Jerker
authors.initials: J
authors.lastname: Fick
authors.affiliation: Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg Gothenburg, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Weijdegård
authors.affiliation: Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg Gothenburg, Sweden.
authors.forename: D G Joakim
authors.initials: DG
authors.lastname: Larsson
keywords: antibiotics; antimicrobial agents; mechanisms of resistance; microbial communities; next generation sequencing