Coatings & surface treatment
Urological catheters are required by around 20% of patients in NHS hospitals.
£200m a year, whereas US data puts the figure at up to $10,197 per patient. Globally, that cost extends to billions of dollars.
Why CAUTI are so common Whatever the challenges, solutions to urinary catheter infections aren’t always available. The good news is that about half of catheter-associated infections are thought to be preventable, essentially by applying the right kinds of infection control measures or by eliminating the unnecessary use of catheters. But that leaves the many millions that occur through no fault of the medical team. “The normal flora, which are bacteria that live
on the body, are easily transmitted into the urethra during insertion of a catheter,” explains Dr Tim Nichol, a microbiology and biosciences lecturer at Sheffield Hallam University. “Insertion can also cause tissue damage and an immune reaction. But even if everything goes really well, the very fact that you’ve got this foreign object inside the body disrupts the normal balance of things.” Fundamentally, this is down to basic biology. When the human body encounters a foreign object, it responds to the intrusion by laying down a protein coat onto the surface of the material. Once bacteria start adhering to that protein coat, an infection can easily take root.
“The bacteria involved in urinary tract infections are often things like E. coli, which have adhesins that can attach to the epithelial cells that line the urethra,” says Nichol. “So they bind to the cells, they bind to the surface of the catheter itself, and they are able to form biofilms – communities of bacteria that are physically protected from the immune system.” Biofilms, for their part, are notoriously hard to eradicate, not least because of the presence of ‘persister cells’ – dormant bacteria that shut down
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their metabolic processes and become invulnerable to antibiotics. This means that antimicrobial coatings, a solution sometimes attempted, may prove ineffective. Add in the fact that some bacteria can invade the cells themselves, residing in the tissue that lines the urethra, and it’s easy to see how recurrent infections might occur even once the condition has notionally been treated.
“The other thing is the status of the patients themselves,” Nichol adds. “So if you have very ill or old patients, they can have reduced immune responses. That’s also the case for patients who are on antibiotic regimes for infections elsewhere – taking antibiotics can disrupt their normal flora and allow for more pathogenic organisms to take hold.”
A range of research avenues Although their research is still in its early stages, Nichol, along with Prof Thomas Smith and others at Sheffield Hallam, have a potential solution in mind. They have been working on a new type of catheter coating that could prevent biofilms from forming on its surface. If their coating proves effective, it could lead to a significant reduction in catheter-associated infections.
Their technology is based on sol-gel chemistry, which involves taking liquid precursors and adding an acid catalyst. The liquids start to react together, forming a kind of network within a liquid solvent. As Nichol explains, the end product looks a little bit like nail varnish. “Because it’s a liquid, we can dip it, we can paint
it, we can spray it,” the academic says. “It can be applied onto surfaces very easily, where it sets as an ultra-thin coating. But the important thing is that it’s porous. We can incorporate different antimicrobials into that, and we can alter the formulation to control the release of those products.”
3.5 million
The number of healthcare-
associated infections that take place in the EU every year.
European Centre for Disease Prevention and Control
£142 Science Direct 119
The amount of money that can be saved for each catheter prevented.
Yuliya Alekseeva/
Shutterstock.com
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