title: Correlation between apramycin and gentamicin use in pigs and an increasing reservoir of gentamicin-resistant Escherichia coli.
abstract: OBJECTIVE
  Resistance towards the veterinary drug apramycin can be caused by the aac(3)-IV gene, which also confers resistance towards the important human antibiotic gentamicin. The objectives of this study were to investigate the temporal occurrence and the genetic background of apramycin and gentamicin resistance in Escherichia coli strains from pork, healthy pigs and diagnostic submissions from pigs and to investigate potential relationships to the use of apramycin and gentamicin at farm and national levels.
  
  
  METHODS
  Data on Danish E. coli isolates from healthy pigs (indicator bacteria), diagnostic submissions from pigs (clinical isolates) and pork were obtained from the national surveillance of antimicrobial resistance and from routine diagnostic laboratories. Antimicrobial consumption data were obtained from the Danish Medicines Agency (1997-2000) and from the VetStat database (2001-2004). The genetic background for gentamicin resistance was investigated by PCR. Relationships between antimicrobial usage and resistance were analysed by chi2 test and logistic regression.
  
  
  RESULTS
  At the farm level, the occurrence of apramycin/gentamicin cross-resistance was correlated to the use of apramycin (P < 0.001). At the national level, occurrence of apramycin/gentamicin cross-resistance in clinical E. coli O149 isolates was significantly correlated with the amounts and duration of apramycin use. The aac(3)-IV gene was detected in all tested cross-resistant isolates.
  
  
  CONCLUSIONS
  Apramycin consumption at farm level is most probably driving the increasing occurrence of apramycin/gentamicin cross-resistant [aac(3)-IV positive] E. coli in diseased pigs and healthy finishers at slaughter. The duration of use and amounts used both had a significant effect on the prevalence of apramycin/gentamicin cross-resistance in diseased weaning pigs at the national level.
authors.affiliation: Department of Epidemiology and Risk Assessment, Danish Institute of Food and Veterinary Research Mørkhøj Bygade 19, DK-2860 Søborg, Denmark.
authors.forename: Vibeke F
authors.initials: VF
authors.lastname: Jensen
authors.forename: Lotte
authors.initials: L
authors.lastname: Jakobsen
authors.forename: Hanne-Dorthe
authors.initials: HD
authors.lastname: Emborg
authors.forename: Anne Mette
authors.initials: AM
authors.lastname: Seyfarth
authors.forename: Anette M
authors.initials: AM
authors.lastname: Hammerum
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology; D003718:Denmark; D024901:Drug Resistance, Multiple, Bacterial; D004363:Drug Utilization / Q000706:statistics & numerical data* / Q000639:trends; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D005839:Gentamicins / Q000008:administration & dosage / Q000494:pharmacology*; D009328:Nebramycin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D013552:Swine / Q000382:microbiology*; D013997:Time Factors; D019155:Veterinary Drugs / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D019155:Veterinary Drugs; D009328:Nebramycin; C011666:apramycin