An improved model for bacterial encrustation studies

A comparative evaluation of various biomaterials for their resistance to bacterial colonization and encrustation in infected urine is an important area in urological biomaterials research. This article describes an in vitro dynamic perfusion system that allows four reactors containing 24 1-in. catheter samples (6 per reactor) to be simultaneously perfused at a constant flow rate by synthetic urine. A common urease-producing urinary pathogen, Proteus mirabilis, was maintained at a level of 10(6) colony-forming units/mL for 7 days in the dynamic perfusion reactors. The pH and bacterial population were monitored every 24 h and the percentage of encrustation on latex and hydrogel-coated commercial catheter materials gave reproducible results in three different runs, 15.2 +/- 3.65% and 13.8 +/- 2.58%, respectively. A major issue of inlet clogging due to ascending bacteria or ammonia has been rectified using a dismountable inlet assembly. An incubator coupled with a cooling system allowed accurate temperature maintenance of 37 degrees C in all four reactors. Results from scanning electron microscopy of some latex samples are also presented.