[Source: Antimicrobial Agents and Chemotherapy, full page: (LINK). Abstract, edited.]
Functional characterization of a Miniature Inverted Transposable Element at the origin of mcr-5 gene acquisition in Escherichia coli
Nicolas Kieffer, Patrice Nordmann, Yves Millemann, Laurent Poirel
Plasmid-mediated colistin resistance of the MCR type is a growing concern in Enterobacteriaceae since it has been described worldwide either in humans and in animals. Here we identified a series of MCR-producing Escherichia coli isolates, corresponding to two different clones (respectively represented by isolates PS1 and PS8b) producing MCR-1 and MCR-5, respectively, from pig fecal samples in France. Plasmid analysis showed that the plasmid carrying the mcr-1 gene (pPS1) possesses an IncHI2 backbone whereas the mcr-5gene was carried onto a 6,268 bp non-typeable, non self-conjugative plasmid (pPS8b). Detailed analysis of plasmid pPS8b revealed a 3,803 bp-long cassette containing the mcr-5 gene that was bracketed by two inverted-repeat sequences (IRs) with 5-bp long direct repeats at each extremity, similarly to an insertion sequence, but with the exception that no transposase gene was identified within this cassette. By performing in-vitro transposition experiments, we showed that the mcr-5 cassette could be mobilized by the TnAs1 transposase provided in-trans, displaying a similar mobilization mechanism as miniature inverted repeat transposable elements (MITEs).
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Keywords: Antibiotics; Drugs Resistance; Colistin; E. Coli; MCR5; Plasmids.