Catheters lined with small points, such as shark fins, can reduce urinary tract infections

Small spines shaped like shark fins can reduce the number of urinary tract infections in patients with catheters.

These flexible hollow tubes, made of plastic, drain urine from the bladder into a bag for bed-bound hospital patients who cannot go to the toilet. They are also used to monitor how much urine a patient passes or to ensure that the bladder does not become too full during surgery.

However, the longer a catheter is in place, the more likely it is to develop a urinary tract infection.

The new catheters have thousands of points, so small they are barely visible to the naked eye, covering the inside of the tube; each point also points posteriorly (towards the end of the tube leaving the body).

This creates a kind of obstacle course that makes it virtually impossible for infection-causing bacteria to crawl through the inside of the catheter to the urinary tract or bladder.

The bacteria are captured by the spines and then washed away by the urine.

Around one in five NHS hospital patients need to be fitted with a urinary catheter. An estimated 90,000 people in the community also have them.

Many are men with severe benign prostatic hyperplasia, where the prostate becomes enlarged and presses on the urethra – the tube that carries urine out of the body.

This can cause urinary retention: in severe cases, the urine ends up in the kidneys and causes long-term damage. To prevent this, a catheter is often left in place for months until men undergo surgery to reduce the size of the prostate.

A study by scientists at Public Health England, published in 2019, found that around 50,000 catheter-related urinary tract infections occur in NHS hospitals every year. The annual cost to the NHS of treating them is around £200 million.

Once insects get into a catheter, they form a slimy film that grows along the lining until it reaches the urinary tract and bladder – where bacteria thrive in the moist environment.

Catheters are often coated with antibiotics or metals such as silver to kill microbes. However, a growing number of bacteria are developing resistance to antibiotics.

The shark fin spikes – developed at the California Institute of Technology in the US – came about after researchers used an artificial intelligence computer program to work out which type of surface was likely to be best at stopping the spread of bacteria.

Around one in five NHS hospital patients need to be fitted with a urinary catheter. An estimated 90,000 people in the community also have them (stock photo)

The AI ​​software simulated what would happen with different surface textures – and identified shark fin-type peaks as the best solution.

The researchers used a 3D printer to build a prototype and tested it with fluid containing E. coli bacteria – the most common source of infections caused by catheters.

The results, published in the latest issue of Applied Sciences, showed that the build-up of bacteria on the catheter’s lining over a 24-hour period was less than 1 percent of what is normally seen with standard catheters without special linings. Clinical trials will start soon.

Chris Eden, professor of urology at the Royal Surrey County Hospital, welcomed the findings but warned that some infection-causing bacteria in a catheter move slightly differently than the E. coli the researchers tested. He told Good Health: ‘This is an exciting breakthrough, but it may not work for all bacteria known to colonize catheters.’