title: Effects of two simulated oxytetracycline dosing regimens on horizontal transfer of antimicrobial resistance plasmids in an in vitro pharmacodynamic model.
abstract: OBJECTIVE
  To evaluate the impact of oxytetracycline exposure on horizontal transfer of an antimicrobial resistance plasmid.
  
  
  METHODS
  Populations of Salmonella enterica subsp enterica serovar Typhimurium and Escherichia coli.
  
  
  METHODS
  Mixed populations of plasmid donor (Salmonella Typhimurium) and recipient (E coli) bacteria were assigned to 1 of 2 simulated oxytetracycline dosing regimens (high peak concentration-short elimination half-life [HC-SHL] or low peak concentration-long elimination half-life [LC-LHL]) or served as untreated control replicates. Donor, recipient, and transconjugant (E coli that acquired the plasmid) bacteria populations were quantified at 12, 24, and 36 hours after oxytetracycline administration by use of culture on selective bacterial growth media.
  
  
  RESULTS
  The ratio of transconjugant to donor bacteria was significantly reduced in the oxytetracycline-exposed replicates, compared with the ratio for the control replicates, at 12 hours. At 24 and 36 hours, results for the HC-SHL regimens were not significantly different from results for the respective control replicates, and results for the LC-LHL regimens also were not significantly different from results for the respective control replicates. The oxytetracycline concentration at these time points (12 hours in the HC-SHL regimen and all 3 time points in the LC-LHL regimen) were in excess of the minimum inhibitory concentration of the recipient bacteria.
  
  
  CONCLUSIONS
  Transfer of antimicrobial resistance plasmids may be suppressed in vitro by oxytetracycline exposure at concentrations greater than the minimum inhibitory concentration of the recipient bacteria.
authors: Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
authors: Brian V
authors: BV
authors: Lubbers
authors: Greg J
authors: GJ
authors: Peterson
authors: Sanjeev K
authors: SK
authors: Narayanan
authors: James A
authors: JA
authors: Havel
authors: Johann F
authors: JF
authors: Coetzee
authors: Michael D
authors: MD
authors: Apley
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D008826:Microbial Sensitivity Tests; D010118:Oxytetracycline / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D010957:Plasmids; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics*; D012641:Selection, Genetic; D013753:Tetracycline Resistance
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D010118:Oxytetracycline