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Triclosan diffused through silicone catheter balloons and produced urinary concentrations that prevented catheter encrustation by P. mirabilis and biofilm formation by several other common pathogens of the catheterized urinary tract. It had little effect on urease-producing P. aeruginosa, S. marcescens or M. morganii but these species did not produce alkaline urine or crystalline biofilms.

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Clinical isolates of Proteus mirabilis causing catheter encrustation and blockage are susceptible to the biocide triclosan (MICs of 0.2 mg/liter). Studies with laboratory models of the bladder have demonstrated that the inflation of catheter retention balloons with triclosan solutions rather than water results in the diffusion of triclosan from the balloons into the surrounding urine and the inhibition of catheter encrustation by P. mirabilis. The aim of this study was to test whether the exposure of P. mirabilis to triclosan under laboratory conditions resulted in the selection of strains with reduced susceptibilities to this biocide. Exposure to triclosan in agar was shown to select mutants with MICs elevated from 0.2 mg/liter up to 80 mg/liter. In a selection of 14 of these strains, the decreased susceptibility was found to be stable and not associated with increased resistance to antibiotics. Experiments with the laboratory models demonstrated that inflation of the catheter balloons with triclosan (10 mg/ml) prevented encrustation and blockage by the parent strain P. mirabilis B2 (MIC, 0.2 mg/liter) and the mutant strain M48 (MIC, 2.0 mg/liter) but had no effect on crystalline biofilm formation by strain M55 (MIC, 40 mg/liter). These results suggest that, in any clinical trial or subsequent clinical use of the strategy, it will be important to monitor the urinary flora of the catheterized patients for P. mirabilis strains with reduced susceptibility to triclosan. The emergence of these strains could undermine the ability of the triclosan strategy to control catheter encrustation.Several studies have reported that the care of half of the many patients undergoing long-term bladder catheterization is compromised when the flow of urine through the catheter is blocked by encrustation (11,13,27). The problem stems from infection by urease-producing bacteria, particularly Proteus mirabilis (7,12,19). These organisms colonize catheters, producing biofilm communities embedded in a polysaccharide gel matrix. The urease they produce hydrolyzes urea to ammonia, elevating the pH of the urine and the biofilm. Under the resulting alkaline conditions, crystals of calcium and magnesium phosphates form in the urine and a crystalline biofilm develops on the catheter (20). This material can block the eyehole and lumen of the catheter, preventing the flow of urine from the bladder and putting the health and welfare of the patient at risk. All types of urinary catheters are vulnerable to encrustation, and currently there are no effective methods available to clinical staff to control the problem (13, 21).Strains of P. mirabilis causing catheter encrustation have been shown to be very sensitive to the biocide triclosan, with MICs of 0.2 mg/liter (9). A strategy to control catheter encrustation has been developed in which triclosan can be delivered directly into the residual urine in the catheterized bladder (25). Laboratory studies with models of the catheterized bladder inoculated with P. mirabilis demonstrated that when the rete...