title: Sequence types and plasmid carriage of uropathogenic Escherichia coli devoid of phenotypically detectable resistance.
abstract: OBJECTIVE
  Plasmids play a major role in the dissemination of antibiotic resistance, and several studies have shown the association between specific resistance mechanisms and certain plasmid types and/or Escherichia coli lineages. This study describes the distribution of plasmids, replicon types, sequence types (STs) and ST complexes (STCs) of E. coli devoid of phenotypic resistance to 24 antibiotics.
  
  
  METHODS
  Eighty E. coli isolates from urinary tract infections from four European countries were selected because of their lack of phenotypically detectable antibiotic resistance. The isolates were characterized to the phylogenetic group level using PCR and to ST by multilocus sequence typing. Plasmid carriage was assessed using S1 nuclease PFGE profiling and PCR-based replicon typing.
  
  
  RESULTS
  Plasmids were detected in only 38/80 (47%) of the isolates; one (n = 18), two (n = 14), three (n = 5) and four (n = 1) plasmids. Six different replicon types were identified, the most common being a combination of IncFII and IncFIB. Most isolates belonged to phylogenetic group B2 and STC73 (n = 20), STC95 (n = 7) and ST420 (n = 6). A high proportion of STC73 isolates (75%) was devoid of plasmids. No association could be found between specific STs and replicon type.
  
  
  CONCLUSIONS
  A large proportion of E. coli strains phenotypically devoid of antibiotic resistance were plasmid naive. Those isolates that harboured plasmids displayed replicon types similar to those of resistant isolates, but the distributions of STs and STCs were different. This may indicate chromosomally encoded mechanisms important for the stabilization of plasmids harbouring antibiotic resistance.
authors: Department of Clinical Microbiology, Central Hospital, Växjö, Sweden. stina.bengtsson@ltkronoberg.se
authors: Stina
authors: S
authors: Bengtsson
authors: Umaer
authors: U
authors: Naseer
authors: Arnfinn
authors: A
authors: Sundsfjord
authors: Gunnar
authors: G
authors: Kahlmeter
authors: Martin
authors: M
authors: Sundqvist
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004927:Escherichia coli Infections / Q000382:microbiology*; D005060:Europe; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D010957:Plasmids; D016133:Polymerase Chain Reaction; D014552:Urinary Tract Infections / Q000382:microbiology; D056689:Uropathogenic Escherichia coli / Q000145:classification* / Q000187:drug effects / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents