Mathur, S.; (2007) A study of urinary catheter encrustation in patients with Proteus urinary tract infection. Doctoral thesis , University of London.

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Abstract

The most common cause of encrustation and blockage of long term urinary catheters is colonisation of the urinary tract by Proteus spp. However, the degree of encrustation experienced by those with Proteus colonisation differs markedly between individuals. This study assessed the range of problems experienced by those colonised by Proteus and the factors which may differentiate severe from mild encrustation in this group. 21 long term catheter users found to have Proteus on urine screening were followed for approximately 3 months with weekly microbiological and chemical urine analysis and examination of their catheters. There was considerable variation in catheter lifespan within and between individuals. Some with persistent Proteus colonisation had no encrustation problems, others experienced frequent catheter blockage. Proteus was usually a stable component of urinary and catheter flora. Rapid encrustation was associated with a lowered nucleation pH (pHn). There was no clear difference in voided pH (pHv) between rapid and slow encrusters, but rapid blockers had a lower mean safety margin (pHn - pHv). pHv was not a useful predictor of catheter blockage. pHn was variable within and between individuals, but was higher in those who encrusted slowly. It was dependent on the calcium concentration and, to a lesser extent, the magnesium concentration of urine, with rapid encrusters having higher urinary calcium. Proteus isolates were assessed for urease activity. Strains with higher urease activities produced more alkaline urine, but this did not clearly result in shorter catheter lifespans. Proteus isolates from catheter users were found to have greater antibiotic resistance, particularly to trimethoprim and amoxicillin, than other local urinary tract isolates. Courses of antibiotic appeared ineffective at altering the urinary flora. The source of Proteus urinary colonisation, examined using Dienes typing and pulsed field gel electrophoresis of bacterial DNA, was commonly found to be the subject's own intestinal flora.

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