Some observations on the diffusion of antimicrobial agents through the retention balloons of foley catheters

We examined the ability of antimicrobial agents to diffuse through the retention balloons of urinary catheters and inhibit their encrustation by Proteus mirabilis.

An agar diffusion screening test was developed to detect agents capable of diffusing through catheter balloons and inhibiting the growth of P. mirabilis. The effect of inflating the balloons with antibacterials on the ability of P. mirabilis to encrust catheters was tested in laboratory models of the catheterized bladder.

Of 18 antimicrobial agents active on P. mirabilis only mandelic acid, phenoxyethanol, nalidixic acid and triclosan diffused through all-silicone catheter balloons to produce zones of inhibition against P. mirabilis. Polyurethane balloons were permeable to gentamicin and fluoroquinolones. Experiments with silicone catheters showed that inflating balloons with mandelic acid (100 gm/l) or ciprofloxacin (10 gm/l) failed to extended the time at which catheters became blocked in models inoculated with P. mirabilis. However, nalidixic acid (50 gm/l) significantly extended the lifespan of catheters (p <0.05). Triclosan (10 gm/l) prevented the increase in urinary pH that induces crystal formation and inhibited the formation of crystalline biofilm, enabling the catheters to drain freely for the full 7-day experimental period.

Inflation of silicone catheter retention balloons with solutions of nalidixic acid or triclosan rather than water should be considered as strategies to control catheter encrustation. Polyurethane balloons are more permeable than silicone balloons to gentamicin and the fluoroquinolones, and they should be investigated as an alternative to silicone or latex in catheter manufacture.