title: Evolution of multi-resistance plasmids in Australian clinical isolates of Escherichia coli.
abstract: Plasmids allow the movement of genetic material, including antimicrobial resistance genes, between bacterial species and genera. They frequently mediate resistance to multiple antimicrobials and can result in the acquisition by a pathogen of resistance to all or most clinically relevant antimicrobials. Unfortunately, there are still large gaps in our understanding of how new multi-resistance plasmids evolve. Five Australian clinical institutions collaborated in this study of multi-resistance plasmids in clinical isolates of Escherichia coli. We characterized 72 resistance plasmids in terms of the antimicrobial resistance profile they conferred, their size and their incompatibility group. Restriction fragment length polymorphisms were used to determine the genetic relationships between the plasmids. Relationships between the host cells were determined using multi-locus enzyme electrophoresis. A lack of correlation between the evolutionary history of the host cells and their plasmids suggests that the horizontal transfer of resistance plasmids between strains of E. coli is common. The resistance plasmids were very diverse, with a wide range of resistance profiles and a lack of discrete evolutionary lineages. Multi-resistance plasmids did not evolve via the co-integrative capture of smaller resistance plasmids; rather, the roles of recombination and the horizontal movement of mobile genetic elements appeared to be most important.
authors.affiliation: Division of Botany and Zoology, School of Life Sciences, Daley Rd, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Miranda
authors.initials: M
authors.lastname: Sherley
authors.affiliation: Division of Botany and Zoology, School of Life Sciences, Daley Rd, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Gordon
authors.affiliation: Department of Microbiology and Infectious Diseases, The Canberra Hospital, Garran, Canberra, ACT 2605, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Collignon
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001315:Australia; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology*; D019143:Evolution, Molecular; D006801:Humans; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length
chemical_list: D000900:Anti-Bacterial Agents