An improved model for bacterial encrustation studies

Abstract

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.

Validation of the CDC biofilm reactor as a dynamic model for assessment of encrustation formation on urological device materials

“…Finlayson and Dubois14 proposed the first in vitro model that took account of both factors, with both a constant flow of artificial urine and a stirring baffle in place. A number of adaptations of this model have been developed utilizing both human15 and artificial urine 16. The use of a modified Robbins device to model encrustation deposition under conditions of continuous flow has also been described 5.…”

Characterization and optimization of experimental variables within a reproducible bladder encrustation model and in vitro evaluation of the efficacy of urease inhibitors for the prevention of medical device‐related encrustation

“…As a result of the clinical importance of encrustation, there is a demand for the development of encrustation‐resistant biomaterials for the manufacture of urological devices. While the identification of such materials may be performed using an in vivo (animal) model, the use of in vitro models for the initial evaluation of the rate and extent of encrustation onto biomaterials has been reported 1, 2, 5–7. In the design of urinary encrustation models, two fundamental experimental parameters require consideration, namely the composition of the artificial urine and the rate of urine flow/stirring.…”

“…In the design of urinary encrustation models, two fundamental experimental parameters require consideration, namely the composition of the artificial urine and the rate of urine flow/stirring. Several encrustation models have employed a range of media including, the urine of healthy volunteers to which an infecting microorganism was added,8 infected artificial urine6 or artificial urine to which urease was added to mimic the presence of urease‐producing microorganisms 5, 7. The main disadvantage of human urine is that the composition will change depending on the patient source, resulting in uncontrollable experimental variations.…”

Assessment of urinary tract biomaterial encrustation using a modified Robbins device continuous flow model

“…The models described by Schmitz et al, 11 Getrial encrustation in the ureter. Biomaterials 17:1025 -liffe, 12 and Sarangapani et al 13 are also unsuitable for long- 1029; 1996. term in vitro encrustation studies because they require large used for studies on the development and control of bacterial…”

“…collecting container. In contrast to these models, Sarangapani et al 13 used a continuous flow apparatus consisting…”