Does drinking cranberry juice produce urine inhibitory to the development of crystalline, catheter-blocking Proteus mirabilis biofilms?

Objective To test the recommendation that to avoid the complications of lon g-term indwelling bladder catheterization (e.g. encrustation and blockage b y crystalline Proteus mirabilis biofilms) patients should drink cranberry j uice. Materials and methods Urine was collected from groups of volunteers who had drunk up to 2 x 500 mL of cranberry juice or water within an 8-h period. L aboratory models of the catheterized bladder were supplied with urine from these groups and inoculated with P. mirabilis. After incubation for 24 or 4 8 h, the extent of catheter encrustation was determined by chemical analysi s for calcium and magnesium. Encrustation was also visualized by scanning e lectron microscopy. Results The amounts of calcium and magnesium recovered from catheters incub ated in urine pooled from individuals who had drunk 500 mL of cranberry jui ce was not significantly different from that on catheters incubated in pool ed urine from control subjects who had drunk 500 mL of water. However. ther e was significantly less encrustation (P=0.007) on catheters from models re ceiving urine from volunteers who had drunk 2 x 500 mL of water than on cat heters incubated in models supplied with urine from volunteers who had drun k 2 x 500 mL of cranberry juice. The amounts of encrustation on these two g roups of catheters were also significantly less than that on catheters incu bated in models supplied with urine from volunteers who had not supplemente d their normal fluid intake, (P < 0.001). Experiments in the models using a rtificial urine showed that increasing the low fluid intake (720 mL/24 h) c haracteristic of many patients undergoing long-term catheterization by fact ors of three and six, significantly (P<0.01) reduced the amounts of calcium and magnesium that formed on catheters. At a simulated fluid intake of 720 mL/24 h, catheters blocked with encrustation after a mean of 42.5 h, while those supplied with urine produced from an intake of 4320 mL/24 h, drained freely for > 10 days. Conclusion In this in vitro Study, drinking cranberry juice did not produce urine that was inhibitory to the development of crystalline catheter-block ing P. mirabilis biofilms. The important factor in preventing catheter encr ustation is it high fluid intake.