Biofilm removal from silicone tubing: an assessment of the efficacy of dialysis machine decontamination procedures using an in vitro model.

The aim of this study was to assess the efficacy of 21 decontamination procedures, for the removal of a multispecies biofilm. Experiments were performed on five-day-old biofilms grown inside silicone tubing, using a reactor system that mimics a dialysis machine. The treatments were tested on 5 cm tubing samples. Effects of treatment were measured using direct microscopy following staining. Bacterial viability and endotoxin removal were determined using conventional microbiological methods following biofilm detachment by scraping. The 21 procedures were classified into four groups based on the amount of biofilm removed. The most effective treatment was an acid pre-treatment, followed by use of a concentrated bleach solution. Acid pre-treatment removes calcium and magnesium carbonate crystals that are always found in dialysis biofilms. Treatments performed at high temperature did not increase the efficacy of biofilm removal. Most treatments caused at least a 10(5)-fold reduction in bacterial viability with a few resulting in complete kill. Autoclaved and bleach-treated samples gave the best results for viability reduction, with both treatments providing an equally effective and complete kill. In addition, autoclaving led to a significant decrease in endotoxin level (removal of 99.99%).

Application of flowcell technology for monitoring biofilm development and cellulose degradation in leachate and rumen systems.

In this study, a flat plate flowcell was modified to provide a reactor system that could maintain anaerobic, cellulolytic biofilms while providing the data needed to carry out a chemical oxygen demand mass balance to determine the cellulose digestion rates. The results showed that biofilms could be observed to grow and develop on cellulose particle surfaces from both anaerobic digester leachate and rumen fluid inocula. The observations suggest that the architecture of rumen and leachate derived biofilms may be significantly different with rumen derived organisms forming stable, dense biofilms while the leachate derived organisms formed less tenacious surface attachments. This experiment has indicated the utility of flowcells in the study of anaerobic biofilms.

Methods for biofilm analysis on silicone tubing of dialysis machines.

We describe an analytical protocol to study biofilms that develop inside silicone tubing of dialysis machines. This protocol has been set up with the help of a dynamic testing device reproducing dialysis conditions. The methodology includes direct microscopic observation, biofilm removal with an original mechanical biofilm scraper, quantitative analysis with culturable and total bacteria counting, and endotoxin level measurement using the LAL chromogenic kinetic assay. The analytical protocol has been assessed on 13 different clinical tubing samples. Most samples were contaminated by adherent cells and the thickest biofilms were found at the connection between the dialysis water distribution loop and the dialysis machine. The less contaminated samples had been removed from dialysis machines that were decontaminated with citric acid and autoclaving, showing the importance of the decontamination procedure for the prevention of biofilm development. This article shows that easy, rapid, reproducible, and economical methods are applicable for a routine analysis of biofilms that develop on dialysis systems and should be included in the regular control of the microbiological quality of dialysis liquids.