title: Spontaneous loss of antibiotic-resistant plasmids transferred to Escherichia coli in experimental chronic bladder infection.
abstract: BACKGROUND
  We investigated whether Escherichia coli that has been transformed with antibiotic-resistant plasmids spontaneously loses the plasmids while infecting the rat bladder.
  
  
  METHODS
  A nontransmissible antibiotic-resistant plasmid was transferred to a clinically isolated strain of E. coli. A knotted thread holding the strain was implanted into the bladder of male Wistar rats. One or 4 weeks later, the total number of bacteria and that of plasmid-carrying bacteria were measured in the bladder.
  
  
  RESULTS
  When plasmid-carrying E. coli alone was inoculated, most of the plasmid-carrying E. coli were replaced with plasmid-free E. coli. When plasmid-carrying and plasmid-free E. coli were simultaneously inoculated, this replacement was accelerated.
  
  
  CONCLUSIONS
  These results suggest that E. coli carrying antibiotic-resistant plasmids spontaneously lose the plasmids as time passes, and thus become sensitive to antibiotics.
authors.affiliation: Department of Urology, Shinshu University School of Medicine, Matsumoto, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D000818:Animals; D001431:Bacteriological Techniques; D002908:Chronic Disease; D004269:DNA, Bacterial / Q000378:metabolism; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000235:genetics*; D004927:Escherichia coli Infections / Q000188:drug therapy*; D008297:Male; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D001745:Urinary Bladder Diseases / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial