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.

Whole genome sequencing reveals high-resolution epidemiological links between clinical and environmental Klebsiella pneumoniae

“…Both mutations occurred in the quinolone resistance-determining region (QRDR) of gyrA and parC [36, 37]. These point mutations were only found in clinical isolates, although both have been detected previously in E. coli isolated from aquatic environments [38]. The aminoglycoside resistance genes were noted to have been acquired on multiple occasions throughout the phylogenetic tree.…”

Characteristics of Quinolone Resistance in Escherichia coli Isolates from Humans, Animals, and the Environment in the Czech Republic

“…Isolates from poultry and rooks that displayed clinical levels of ciprofloxacin resistance linked to single or double mutations in gyrA and parC were found in our study. Strains of various animal origin with these types of mutations have been recently found worldwide (Sáenz et al, 2003; Liu et al, 2012; Castillo et al, 2013; Johnning et al, 2015; Balakrishnan et al, 2016). …”

Determinants of Genetic Diversity of Spontaneous Drug Resistance in Bacteria

“…While resistance mutations typically impair growth to a certain extent (Schrag et al 1997;Reynolds 2000), some can be advantageous even in the absence of the drug (Luo et al 2005;Marcusson et al 2009;Vickers et al 2009;Baker et al 2013;Miskinyte and Gordo 2013;Rodríguez-Verdugo et al 2013). In addition, there is a growing concern regarding the selection for resistance under the nonlethal antibiotic concentrations commonly found in many clinical and natural environments (Gullberg et al 2011;Andersson and Hughes 2014;Larsson 2014;Johnning et al 2015).…”