Objective: To test the resistance of currently available types of indwelling urethral catheters to blockage by encrustation with mineralized Proteus mirabilis biofilms.
Materials and methods: Encrustation was studied in a simple laboratory model of the catheterized bladder. Artificial urine was supplied to the bladder chamber at 0.5 mL/min. The bladder urine was inoculated with a clinical strain of P. mirabilis that had been isolated from an encrusted catheter. The models were operated until the catheters blocked and atomic absorption spectrometry was used to assess the amounts of calcium and magnesium deposited on the catheters. Scanning electron microscopy was also used to locate and assess the degree of encrustation.
Results: The mean times to blockage ranged from 21 h for the Bard hydrogel/silver-coated latex catheter to 56 h for the Eschmann Folatex S all-silicone catheter. The calcium and magnesium salts were mainly deposited on the 10 cm below the eye-holes of the catheters, complete blockage generally occurring in the 2 cm immediately below the eye-hole.
Conclusion: None of the 18 types of catheter tested, including those coated with hydrogel or silver, were capable of resisting encrustation by P. mirabilis biofilm.