Abstract
As small, mobilizable replicons with a broad host range, IncQ plasmids are widely distributed among clinical and environmental bacteria. They carry antibiotic resistance genes, and it has been shown that they confer resistance to β-lactams, fluoroquinolones, aminoglycosides, trimethoprim, sulphonamides, and tetracycline. The previously proposed classification system divides the plasmid group into four subgroups, i.e., IncQ-1, IncQ-2, IncQ-3, and IncQ-4. The last two subgroups have been poorly described so far. The aim of this study was to analyze five newly identified IncQ-3 plasmids isolated from a wastewater treatment plant in Poland and to compare them with all known plasmids belonging to the IncQ-3 subgroup whose sequences were retrieved from the NCBI database. The complete nucleotide sequences of the novel plasmids were annotated and bioinformatic analyses were performed, including identification of core genes and auxiliary genetic load. Furthermore, functional experiments testing plasmid mobility were carried out. Phylogenetic analysis based on three core genes (repA, mobA/repB, and mobC) revealed the presence of three main clusters of IncQ-3 replicons. Apart from having a highly conserved core, the analyzed IncQ-3 plasmids were vectors of antibiotic resistance genes, including (I) the qnrS2 gene that encodes fluoroquinolone resistance and (II) β-lactam, trimethoprim, and aminoglycoside resistance genes within integron cassettes.
Highlights
In the natural environment, as a result of the presence of subminimal inhibitory concentrations of antibiotics, resistance genes encoded by mobile genetic elements, such as plasmids, transposons, and integrons, can be disseminated through horizontal gene transfer (HGT) [1,2,3,4,5,6]
Based on an analysis of their replication systems, the plasmids were classified into the IncQ-3 subgroup
IncQ plasmids belong to a group of widely distributed replicons, occurring mostly in aquatic environments, including wastewater treatment plants, hospital effluents, and clinical samples
Summary
As a result of the presence of subminimal inhibitory concentrations of antibiotics, resistance genes encoded by mobile genetic elements, such as plasmids, transposons, and integrons, can be disseminated through horizontal gene transfer (HGT) [1,2,3,4,5,6]. Wastewater treatment plants (WWTPs) are the entry routes for antibiotic-resistant bacteria (ARBs), including pathogenic and multidrug-resistant (MDR) strains [7]. As sites where both antibiotics and favorable conditions for bacterial growth occur, WWTPs promote horizontal gene transfer (HGT) [8,9]. The occurrence of a similar gene pool at different stages of wastewater treatment is caused by the fact that antibiotics, especially fluoroquinolones, trimethoprim, or sulfonamides, are poorly removed during the wastewater treatment process
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