[An improved model of a catheterised human bladder for screening bactericidal agents]

Catheter encrustation and associated blockage by a crystalline Proteus mirabilis biofilm constitute a continuous problem in long-term catheterised patients. The objective of the present work was to verify a new, physiological bladder model possessing the ability to show that triclosan-blocking solutions exert bactericidal and bacteriostatic activities.

Catheterised sterile infusion bags served as human bladder models. Artificial urine inoculated with Proteus mirabilis was administered by a further aperture. Samples for measurement of pH value and microbial count were collected at intervals of 24 h. Upon completion of testing catheter encrustation was assessed and visualised by scanning electron microscopy.

In contrast to the application of placebo solution, in models filled with triclosan-blocking solution the catheters drained freely for the experimental period. Similar results were obtained for pH values and microbial count. The pH of the artificial urine did not exceed a critical value of pH 7 and the numbers of organisms correspond approximately to the initially inoculated number of organisms.

In the model developed here, triclosan inhibits the growth of Proteus mirabilis over the test period by diffusing into the artificial urine through the catheter balloon. Thus, triclosan acts against the pH increase as well as the formation of a crystalline biofilm. Taken together, the adaptability of this new, physiological model of the human bladder could be shown.