Basic Science: Second Prize Sustained Release Varnish Containing Chlorhexidine for Prevention of Biofilm Formation on Urinary Catheter Surface: In Vitro Study Nandakishore K. Shapur, MBBS, M.S., D.N.B., 1 Mordechai Duvdevani, M.D., 1 * Michael Friedman, Ph.D., 2 Batya Zaks, M.Sc., 3 Irit Gati, M.Sc., 2 Eran Lavy, M.Sc., D.V.M., Dip. ECVPT, 4 Ran Katz, M.D., 1 Ezekiel H. Landau, M.D., 1 Dov Pode, M.D., 1 Ofer N. Gofrit, M.D., Ph.D., 1 and Doron Steinberg, Ph.D. 3 * Abstract Background and Purpose: Biofilms on the surfaces of urinary catheters are among the pivotal factors for recurrent and persistent infections in urology. Many techniques have been investigated and applied for eradication of these biofilms—but with no full success. The aim of this study was to examine the effect of sustained release medicated varnish, releasing chlorhexidine, on the formation of biofilm on the urinary catheter surface in an in-vitro model. Materials and Methods: A batch model was used to test the antibacterial/antibiofilm effect of the sustained release varnish: Catheter pieces coated with sustained release varnishes were placed in bacterial growth medium that was infected with Pseudomonas aeruginosa for 96 hours. Various concentrations of chlorhexidine impregnated in the varnish were tested. After the incubation period, the catheter pieces were assessed for biofilm formation by measuring the optical density, colony-forming units, and using confocal laser scanning microscopy, and electron scanning microscopy. Results: Biofilm growth measurement (colony-forming units [CFU]) on the catheter surface coated with the various concentrations of chlorhexidine in sustained released varnish revealed a 94% reduction with 1% chlorhexidine (P < 0.0001) and 43% reduction with 0.1% chlorhexidine (P = 0.08) coated varnish in comparison with a positive control or the placebo varnish in preventing biofilm growth of P. aeruginosa. These biologic assays were confirmed using confocal and electron microscopy. Conclusions: Of the various tested concentrations of sustained release varnishes, the 1% chlorhexidine con- centration has demonstrated the superior antibiofilm effect on urinary catheters with P. aeruginosa. Although similar varnishes are used in dentistry, it needs extended research in animals before applying this technology in human trials. Introduction M edical prostheses or implantable medical devices are being used as a support in the management of various illnesses. Urinary catheters are among the most commonly used medical devices in medical practice, in hos- pitals, and in nursing homes. More than 5 million patients receive urinary catheters annually in institutional setups, of which more than 40% encounter catheter-associated urinary tract infection (CAUTI). 1,2 CAUTI is the most common nosocomial infection and second most common cause of nosocomial bacteremia. In the majority of cases, CAUTI is asymptomatic, but it can prolong hospitalization and increase hospital expenditure, ranging from $1000 to $2900, and provoke initiation of unnecessary antibiotic regimes, which can lead to multidrug-resistant or- ganisms. CAUTI can progress to pyelonephritis, septicemia, and mortality leading to increases in the institutional death rate 1,3 After a catheter is placed and comes in contact with urine, a conditioning film is formed on the tube, resulting from the deposition of proteins, minerals, polysaccharides, and other host-derived factors in the urine. 4 This resulting surface will provide binding sites for the uropathogens, which initiates 1 Department of Urology, Hadassah Medical Center, Hadassah-Hebrew University, Ein Kerem, Jerusalem, Israel. 2 School of Pharmacy, Hebrew University-Hadassah, Ein Kerem, Jerusalem, Israel. 3 Biofilm Research Laboratory, Institute of Dental Sciences, Hebrew University-Hadassah, Ein Kerem, Jerusalem, Israel. 4 Koret School of Veterinary Medicine, Faculty of Agriculture Food and Environment, Hebrew University, Rehovot, Israel. *These authors contributed equally to the article. JOURNAL OF ENDOUROLOGY Volume 26, Number 1, January 2012 ª Mary Ann Liebert, Inc. Pp. 26–31 DOI: 10.1089/end.2011.0140 26