Visible and UVA light as a potential means of preventing Escherichia coli biofilm formation in urine and on materials used in urethral catheters.

Catheter-associated urinary tract infections are the most common hospital-acquired infection, for which Escherichia coli is the leading cause. This study investigated the efficacy of 385nm and 420nm light for inactivation of E. coli attached to the silicone matrix of a urinary catheter. Using urine mucin media, inactivation of planktonic bacteria and biofilm formation was monitored using silicone coupons. Continuous irradiance with both 385nm and 420nm wavelengths with starting cell density population 10(3)CFU ml(-1) reduced planktonic suspensions of E. coli to below the detection level after 2h and 6h, respectively. Bacterial attachment to silicone was successfully prevented during the same treatment. Inactivation by 385nm and 420nm was found to be dependent on media, cell density and oxygen, with less inhibition on planktonic suspensions when higher starting cell densities were used. In contrast to planktonic suspensions in PBS, continuous irradiance of pre-established biofilms showed a greater reduction in survival compared to urine mucin media after 24h. Enhanced inhibition for 385nm and 420nm light in urine mucin media was associated with increased production of reactive oxygen species. These findings suggest 385nm and 420nm light as a promising antimicrobial technology for the prevention of biofilm formation on urethral catheters.