title: Antibiotic resistance and plasmid transfer capacity in biofilm formed with a CTX-M-15-producing Klebsiella pneumoniae isolate.
abstract: OBJECTIVE
  To characterize a CTX-M-15-producing Klebsiella pneumoniae isolate that was identified during an outbreak involving 16 patients who had undergone endoscopic retrograde cholangiopancreatography between December 2008 and August 2009. The strain was also detected in one endoscope used for these examinations.
  
  
  METHODS
  Disc diffusion assays, MICs and isoelectric focusing were used to characterize the plasmidic CTX-M-15 β-lactamase. PCRs were used to check for the presence of genes associated with virulence or antibiotic resistance. Antibiotic tolerance tests and plasmid transfer were carried out in both planktonic and biofilm conditions.
  
  
  RESULTS
  The strain belonged to sequence type 14 and to the virulent capsular serotype K2, but produced little glucuronic acid. It contained a 62.5 kb conjugative plasmid carrying the bla(CTX-M-15), bla(OXA-1) and aac(6')-Ib-cr genes and harboured few virulence genes (uge, wabG, kfu and mrkD). The strain was highly resistant to cefotaxime (MIC 516 mg/L) and the presence of this antibiotic at sub-MIC concentrations enhanced biofilm formation. The isolate was susceptible to ofloxacin (MIC 2 mg/L), but the bactericidal effect of this antibiotic was greater in planktonic cultures and 6 h old biofilm than in 24 or 48 h old biofilms. The K. pneumoniae strain was notable for its ability to transfer its plasmid, especially in biofilm conditions, in which the rate of plasmid transfer was about 0.5/donor.
  
  
  CONCLUSIONS
  These findings demonstrate the ability of this strain to survive in a hospital environment and to transfer its extended-spectrum β-lactamase-encoding plasmid.
authors.affiliation: Clermont Université, UMR CNRS 6023 'Laboratoire Microorganismes: Génome Environnement (LMGE)',  Université d'Auvergne, F-63000 Clermont-Ferrand,  France.
authors.forename: Claire
authors.initials: C
authors.lastname: Hennequin
authors.forename: Claire
authors.initials: C
authors.lastname: Aumeran
authors.forename: Frédéric
authors.initials: F
authors.lastname: Robin
authors.forename: Ousmane
authors.initials: O
authors.lastname: Traore
authors.forename: Christiane
authors.initials: C
authors.lastname: Forestier
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018441:Biofilms / Q000254:growth & development*; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology; D004196:Disease Outbreaks; D005602:France / Q000453:epidemiology; D022761:Gene Transfer, Horizontal; D006801:Humans; D007710:Klebsiella Infections / Q000453:epidemiology / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics*; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases