Catheter-associated urinary tract infection (CAUTI) is a major concern with rates up to 4.5 per 1,000 urinary catheter-days in adult intensive care units (ICUs). Bloodstream infections (BSIs) from UTIs involve a urinary catheter in up to 71% of cases [1]. There is, to date, no market-stage non-eluting technology to significantly prevent bacterial growth on urinary catheters. The purpose of the present study was to devise a non-eluting antimicrobial surface modification that can be permanently incorporated directly into the silicone coating process of catheters to reduce biofilm formation and associated infections.

Commercially available red-rubber catheters were cut into samples approximately 2 cm in length and sonicated in isopropanol for 15 minutes to clean the surface. In the experimental group (n = 9), catheters were air-dried and mechanically dipped in a proprietary antibacterial solution comprising a commercially available polydimethylsiloxane elastomer and a quaternary ammonium polymer (DBG-21). Samples were dipped 5 times with an upper and lower hang time of 60 seconds at 50,000 um/min. The coating was cured at 70°C for 12 hours. Samples then underwent isopropanol sonication to remove excess coating not covalently bonded to the surface. The control group consisted of uncoated catheters (n = 9). Catheters were sterilized for 1 hour using 70% ethanol. Antibacterial activity was tested with a modified ASTM E2149 protocol after 1 hour of dynamic contact. 1.0 ± 0.1 grams of treated and control catheters were placed in individual 250 mL Erlenmeyer flasks with 49 mL of saline. 1 mL of 1 x 10^6 CFU/mL Staphylococcus epidermidis was added to each flask. The flasks were then shaken at 200 rpm at room temperature for 1 hour, at which point serial dilution and plating was carried out to quantify the bacteria in the solution.

The antibacterial test was run in triplicate on three different sets of control and treated catheters. The antibacterial silicone coating resulted in bacterial reductions of 99.96% compared to control catheters (p = 0.0003). The antibacterial silicone catheters resulted in a 3.46 log reduction in bacterial growth.

Our study demonstrates that significant bacterial growth reduction can be obtained on urinary catheters without the use of eluting heavy metals such gold, copper or silver. The present technology is efficient even in the presence of a particularly high bacterial inoculum.

Antibacterial surface modification technology without the use of eluting heavy metals represents an avenue to mitigate the burden of CAUTIs and CAUTI-associated morbidity and mortality. Permanently antibacterial urinary catheters have the potential to significantly decrease BSIs from UTIs, improve patient outcomes and quality of life, as well as mitigate the financial burden of CAUTIs.

Lo E, Nicolle LE, Coffin SE, et al. 2014. Strategies to prevent catheter-associated urinary tract infections in acute care hospitals: 2014 update. Infect Control Hosp Epidemiol 35 Suppl 2:S32-47.

Continence 7S1 (2023) 100734
DOI: 10.1016/j.cont.2023.100734