title: An electrified catheter to resist encrustation by Proteus mirabilis biofilm.
abstract: OBJECTIVE
  We investigated the effect of iontophoresis produced by passing an electric current through silver electrodes attached to catheters on catheter encrustation by crystalline Proteus mirabilis biofilm.
  
  
  METHODS
  Four glass bladder models were catheterized with 16Fr silicone catheters, of which 3 had 0.25 mm silver wires running through and beside the lumen. Two wired catheters had the silver wires connected to a 9 V direct current source supplying a steady current of 150 microA via a self-regulating circuit. Artificial urine, which had been inoculated with a clinical strain of P. mirabilis isolated from an encrusted catheter, was instilled into the bladder model at 0.5 ml per minute. The models were operated until the test catheters became blocked. Mean blockage time was statistically analyzed by ANOVA. Bacterial colony count, silver ions and pH were assessed every 24 hours.
  
  
  RESULTS
  The experiment was repeated 3 times. Time to blockage, colony count, pH and scanning electron microscopy was used to assess encrustation in electrified and control catheters. Time to blockage in electrified vs control catheters was 156 vs 22 hours. The difference in blockage times was statistically significant (p <0.002). The viable bacterial cell count in urine with test catheters vs that in controls was 1.12 x 10(4) vs 2.73 x 10(9) cfu/ml. The pH increased to 9 in control models, whereas it remained less than 6.5 in test models for about 100 hours.
  
  
  CONCLUSIONS
  Electrified catheters released ions in urine that have the oligodynamic property of inhibiting bacterial growth. The application of electric current to catheters fitted with silver electrodes significantly decreased the rate at which these devices became encrusted by P. mirabilis. This principle could be used to prevent encrustation on long-term catheters.
authors.affiliation: Department of Urology, Walsgrave Hospital, University Hospital of Coventry, United Kingdom. anichak@hotmail.com
authors.forename: Aniruddha
authors.initials: A
authors.lastname: Chakravarti
authors.forename: Santha
authors.initials: S
authors.lastname: Gangodawila
authors.forename: Michael James
authors.initials: MJ
authors.lastname: Long
authors.forename: Nicola S
authors.initials: NS
authors.lastname: Morris
authors.forename: Alexander Robert Eadie
authors.initials: AR
authors.lastname: Blacklock
authors.forename: David J
authors.initials: DJ
authors.lastname: Stickler
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D002408:Catheters, Indwelling; D015169:Colony Count, Microbial; D003460:Crystallization; D004558:Electric Stimulation / Q000295:instrumentation*; D004559:Electric Wiring; D004868:Equipment Failure; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007477:Ions; D008855:Microscopy, Electron, Scanning; D008953:Models, Anatomic; D011513:Proteus mirabilis / Q000502:physiology*; D012828:Silicones; D012834:Silver / Q000032:analysis; D016896:Treatment Outcome; D014546:Urinary Catheterization / Q000295:instrumentation*
chemical_list: D007477:Ions; D012828:Silicones; D012834:Silver