Beschreibung:
<jats:title>Abstract</jats:title><jats:sec>
<jats:title>Background</jats:title>
<jats:p><jats:italic>Escherichia coli</jats:italic> carrying clinically important antimicrobial resistances [i.e., against extended-spectrum-beta-lactamases (ESBL)] are of high concern for human health and are increasingly detected worldwide. Worryingly, they are often identified as multidrug-resistant (MDR) isolates, frequently including resistances against quinolones/fluoroquinolones.</jats:p>
</jats:sec><jats:sec>
<jats:title>Results</jats:title>
<jats:p>Here, the occurrence and genetic basis of the fluoroquinolone resistance enhancing determinant <jats:italic>qnrB</jats:italic> in ESBL-/non-ESBL-producing <jats:italic>E. coli</jats:italic> was investigated. Overall, 33 <jats:italic>qnrB</jats:italic>-carrying isolates out of the annual German antimicrobial resistance (AMR) monitoring on commensal <jats:italic>E. coli</jats:italic> (incl. ESBL-/AmpC-producing <jats:italic>E. coli</jats:italic>) recovered from food and livestock between 2013 and 2018 were analysed in detail. Whole-genome sequencing, bioinformatics analyses and transferability evaluation was conducted to characterise the prevailing <jats:italic>qnrB</jats:italic>-associated plasmids. Furthermore, predominant <jats:italic>qnrB</jats:italic>-carrying plasmid-types were subjected to <jats:italic>in</jats:italic> <jats:italic>silico</jats:italic> genome reconstruction analysis. In general, the <jats:italic>qnrB-</jats:italic>carrying <jats:italic>E. coli</jats:italic> were found to be highly heterogenic in their multilocus sequence types (STs) and their phenotypic resistance profiles. Most of them appeared to be MDR and exhibited resistances against up to ten antimicrobials of different classes. With respect to <jats:italic>qnrB</jats:italic>-carrying plasmids, we found <jats:italic>qnrB</jats:italic>19 located on small Col440I plasmids to be most widespread among ESBL-producing <jats:italic>E. coli</jats:italic> from German livestock and food. This Col440I plasmid-type was found to be highly conserved by exhibiting <jats:italic>qnrB</jats:italic>19, a <jats:italic>pspF</jats:italic> operon and different genes of unassigned function. Furthermore, we detected plasmids of the incompatibility groups IncN and IncH as carriers of <jats:italic>qnrB</jats:italic>. All <jats:italic>qnrB</jats:italic>-carrying plasmids also exhibited virulence factors and various insertion sequences (IS). The majority of the <jats:italic>qnrB</jats:italic>-carrying plasmids were determined to be self-transmissible, indicating their possible contribution to the spread of resistances against (fluoro)quinolones and other antimicrobials.</jats:p>
</jats:sec><jats:sec>
<jats:title>Conclusion</jats:title>
<jats:p>In this study, a diversity of different plasmid types carrying <jats:italic>qnrB</jats:italic> alone or in combination with other resistance determinants (i.e., beta-lactamase genes) were found. The spread of these plasmids, especially those carrying antimicrobial resistance genes against highest priority critically important antimicrobial agents, is highly unfavourable and can pose a threat for public health. Therefore, the dissemination pathways and evolution of these plasmids need to be further monitored.</jats:p>
</jats:sec>