Novel Catheter Coating May Provide Early Warning of Infection

In an article published online February 26, 2016 in the journal Biosensors and Bioelectronics, researchers, Scarlet Milo, MChem, and colleagues at academic centers across the United Kingdom, reported results of an in vitro study evaluating a urinary catheter that visibly warns health care providers when an infection is developing.

According to the researchers, an estimated 100 million indwelling urinary catheters are used worldwide each year, approximately 30 million of which are used in the United States alone. Due to the ubiquitous use of indwelling urinary catheters, catheter-associated nosocomial infections are common occurrence in many healthcare settings, and are estimated to burden the United States health care system with $424 million to $450 million in excess costs per year.

An estimated 50% of patients receiving urinary catheters over a long period experience encrustation of blockage of the catheter, which may lead to infection. Such infections are often related to biofilms that form on the surface of catheters. One important pathogen associated with up to 45% of catheter-associated urinary tract infections is Proteus mirabilis, which expresses an enzyme known as ‘urease’ that enables the bacteria to feed on the urea present in urine.

Efforts to reduce the formation of biofilms on urinary catheters include coating the surface of catheters with silver alloys, or impregnating silicone plastic catheters with nitrofurazone—an antibacterial compound. However, meta-analysis indicate that these catheters have little clinical benefit.

Rather than attempting to develop a urinary catheter with an antimicrobial coating, researchers Milo and colleagues developed a catheter coated with a pH-sensitive layer that releases dye during initial formation of a biofilm of Proteus mirabilis.

Using a chemical process, the researchers coated standard catheters with the experimental polymer substance and dye-releasing layer. The catheter was tested with artificial urine, samples of sterile urine, and samples of bacteria-containing urine. In an in vitro model, the researchers pumped urine samples through the pH-sensitive catheter at temperatures similar to those present in the human body.

In catheters exposed to artificial urine inoculated with Proteus mirabilis, color changes were first observable within a mean of 4.2 hours, with catheters reaching a maximum color change intensity within an average of 6.2 hours. Conversely, catheters receiving sterile artificial urine did not show any release of dye, or any color change. Researchers estimated that use of the specialized catheters would provide 10 to 12 hours of advance warning of an infection, potentially reducing the risk of serious complications.

In their conclusion, the researchers noted that the use of a pH-triggered catheter may provide healthcare professionals with early warnings of urinary catheter infection, colonization, and blockage related to Proteus mirabilis biofilms. This system may reduce the cost of care, and improve outcomes for patients at risk of developing this condition.