title: Prospective study of individuals with long-term urinary catheters colonized with Proteus species.
abstract: OBJECTIVE
  To characterize the variability in the times catheters take to block with encrustation in patients who have Proteus in their urinary flora, and to identify factors responsible for modulating the rate of catheter encrustation and blockage.
  
  
  METHODS
  Twenty patients were followed prospectively for > or = 12 weeks, with a bacteriological analysis on weekly urine samples. The pH of the voided urine samples and the pH at which crystals formed in them (the nucleation pH) were determined. Catheters were collected and examined for bacterial biofilm and crystal deposition.
  
  
  RESULTS
  The time that catheters took to block was 2-98 days. The mean pH of the urine voided by patients designated as slow encrusters (6.9) was not significantly different (P = 0.237) from that of rapid encrusters (7.2). However, patients whose catheters took longer to block had a significantly higher mean nucleation pH (8.1 vs 7.3, P = 0.002) and significantly higher mean safety margin between their nucleation pH and voided pH (1.17 pH units vs 0.13, P = 0.003).
  
  
  CONCLUSIONS
  The variation in the rate of catheter encrustation between individuals infected with Proteus is a function of the difference between the voided pH and the nucleation pH of their urine. The value of nucleation pH of an individual's urine varies widely, suggesting it should be possible to devise strategies to increase this value and thus reduce the rate of encrustation in those with urinary tract colonization by urease-positive bacteria.
authors.affiliation: Bristol Urological Institute, Southmead Hospital, Bristol, UK. s.mathur@dial.pipex.com
authors.forename: Sunil
authors.initials: S
authors.lastname: Mathur
authors.forename: Marc T E
authors.initials: MT
authors.lastname: Suller
authors.forename: David J
authors.initials: DJ
authors.lastname: Stickler
authors.forename: Roger C L
authors.initials: RC
authors.lastname: Feneley
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D002408:Catheters, Indwelling / Q000382:microbiology; D003460:Crystallization; D004866:Equipment Contamination; D004868:Equipment Failure; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D011446:Prospective Studies; D011512:Proteus Infections / Q000652:urine*; D011513:Proteus mirabilis / Q000302:isolation & purification; D014546:Urinary Catheterization / Q000009:adverse effects*; D014556:Urine / Q000737:chemistry