title: High frequency transfer and horizontal spread of apramycin resistance in calf faecal Escherichia coli.
abstract: OBJECTIVE
  The aminoglycoside apramycin has been used extensively in animal husbandry in the UK since 1978. This study aimed to determine both whether calves that had never been treated with aminoglycoside antibiotics harboured apramycin-resistant (apr(R)) commensal Escherichia coli, and the mode of spread of the resistance gene.
  
  
  METHODS
  Apr(R) E. coli from weekly calf faecal samples were typed by pulsed-field gel electrophoresis, antibiotic resistance phenotype, plasmid restriction profiles and plasmid transfer frequencies.
  
  
  RESULTS
  During 4 months of weekly sampling, six of 11 calves were found to harbour apr(R) E. coli. All apr(R) E. coli (45) were cross-resistant to gentamicin and tobramycin, which are both used in human medicine. Resistance was conferred by the aac(3)IV gene, present on three different conjugative plasmids. Two of these plasmids also mediated tetracycline and streptomycin resistance. One plasmid demonstrated very high transfer frequencies and was found in three different genotypes.
  
  
  CONCLUSIONS
  We report the presence of apr(R) commensal E. coli in cattle that have never been treated with aminoglycosides. The presence of one conjugative plasmid in three different genotypes is evidence of horizontal spread of this plasmid. This is the first report of a very high transfer frequency of apr(R) plasmid, demonstrating horizontal spread in the commensal flora of food animals.
authors.affiliation: Medical Microbiology, University of Edinburgh Medical School, Edinburgh EH8 9AG, UK. cyates@ed.ac.uk
authors.forename: C M
authors.initials: CM
authors.lastname: Yates
authors.forename: M C
authors.initials: MC
authors.lastname: Pearce
authors.forename: M E J
authors.initials: ME
authors.lastname: Woolhouse
authors.forename: S G B
authors.initials: SG
authors.lastname: Amyes
mesh_terms: D000123:Acetyltransferases / Q000235:genetics; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D016000:Cluster Analysis; D003227:Conjugation, Genetic; D017931:DNA Primers; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics*; D005243:Feces / Q000382:microbiology*; D022761:Gene Transfer, Horizontal; D005838:Genotype; D008826:Microbial Sensitivity Tests; D009328:Nebramycin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000900:Anti-Bacterial Agents; D017931:DNA Primers; D004269:DNA, Bacterial; D009328:Nebramycin; C011666:apramycin; D000123:Acetyltransferases; C045539:aminoglycoside N(3')-acetyltransferase