Disinfection of Biofilms in Tubes with Ultraviolet Light

Bacterial biofilms on long-term catheters are a major source of infection. We demonstrate here the potential of UVC light emitting diodes (LED) for disinfection purposes in catheter like tubes contaminated with biofilm. We show that UVC Light propagation is possible through teflon tubes using the liquid light guiding principle. If the refractive index of the liquid is higher than that of the tube material light is guided inside the tube by internal reflections. To obtain a high refractive index of the liquid sodium chloride in high concentrations is added to the aqueous solution. It is shown that the UVC light attenuation inside the tube can be described by an exponential function depending of tube length and various loss mechanisms. The disinfection efficiency of the UVC diodes is demonstrated on tubes contaminated artificially with a Pseudomonas aeruginosa biofilm. The tubes were connected to a flow system and biofilms were produced during a three day period. Tubes in lengths of 10 cm (FEP teflon) were contaminated. Tubes for control and for UVC treatment were contaminated in parallel. The control and UVC treated tubes were both filled with a 20 % NaCl solution during the UVC treatment time. The applied UVC doses corresponded to treatment times between 15 – 120 min corresponding to UVC fluencies between 8 – 67 mWsec/cm2. Biofilm were sampled from the total inner surface of the control and UVC treated tubes. Colony counts on the control samples were in the range of 4.8103 to 106 CFU/ml. The disinfection rates obtained were to close to 100 % (detection limit: 10 CFU/ml). Based on the our investigations we conclude that there is a potential of using LED UVC light sources for disinfection of tubes with thin or transparent biofilms.