Sodium Hypochlorite is Effective against Biofilms in Dialysis Equipment

To test the efficacy of chemical disinfectants against bacterial biofilms in hemodialysis equipment, a Center for Disease Control and Prevention (CDC)-Biofilm Reactor was used to create biofilms. Methylobacterium radiotolerance was isolated from the hemodialysis fluid and used as the test organism. We examined the efficacy of sodium hypochlorite (NaOCl) in elimination of planktonic cells compared to that in the case of biofilms. Planktonic bacteria were completely eliminated at 50 parts per million (ppm) of NaOCl, which is the lowest concentration for clinical use. The viable cell count in the biofilm reached its minimum value around a logarithmic reduction value (LRV) of 6, when the concentration was raised to 1000 ppm and the reaction time was extended by 1 hour or more. Furthermore, at 200 ppm, the LRV was elevated depending on the time. And the LRV while maintaining static conditions for 6 hours at 200 ppm was similar to that of short time at 1000 ppm. These results suggest that NaOCl has sufficient bactericidal activity even for biofilms at a practical concentration and reaction time, and that the CDC-Biofilm Reactor is an effective tool for finding useful disinfection conditions.