Bacteria-resistant coating for catheters

Each of us produces a couple of litres of urine a day, and getting rid of it isn’t normally a problem for a healthy person. But some people can’t pass water this way and need help, either in the short term or for longer periods of time. This is where a urinary catheter comes in. This is a flexible rubber tube that is inserted along the urethra to remove urine directly from the bladder. But a big problem with catheters is that, in doing this, they can introduce infection. But now researchers at the University of Nottingham have developed a bacteria-resistant coating for these devices to cut down the risk. Andrew Hook is one of the developers and joined Chris Smith on the show.

Chris - How big a problem is it that you're trying to solve here? How many people succumb to these sorts of issues?

Andrew - Yes. So it's a big problem. Generally speaking, there's about 3 to 5 percent for people who have to use a urinary catheter and this can be, hundreds of thousands of people will use a urinary catheter each year within the U.K. You can do the math there. This is a problem that affects lots of people, and it's also a big cost to the NHS. It's estimated to cost up to two and a half billion pounds per year to treat.

Chris - And why is it a problem? Why does this happen? Why should putting a catheter that is sterile, it comes out of a sterile packet into the body, why should that lead to a higher risk of infection?

Andrew - When you put a device into the body, what that allows bacteria to do is, usually the bacteria  are what we call planktonic, or a single bacteria and the body's pretty good at dealing with these. And what happens when you have a device, this is a surface the bacteria are able to attach, they’re then able to form what we call biofilm. You may have come across a biofilm before actually we're just talking about dental hygiene. Actually dental plaque is a type of biofilm, and when bacteria form biofilm they’re up to a thousand times more difficult to treat by antibiotics, or your host's immune system. And it's the ability of bacteria to attach to medical devices that causes this biofilm. This is what causes these persistent infections associated with these devices.

Chris - So in an ideal world we would like some kind of catheter, or material to make catheters and other plasticware that we put into the body, that does not allow bacteria to cling on in the first place, or assemble these protective biofilms that insulate them from either the body's own immune system, or the antibiotics that we try and get rid of them with.

Andrew - Yeah. So that's exactly the strategy that we were trying to take, we'd like to prevent the bacteria from being able to form these biofilms at all. And then that would allow the immune system to be able to deal with the bacteria, if the bacteria are able to invade the body at all.

Chris - And you reckon you've got something that fits the bill?

Andrew - Yeah. So we've been able to develop a polymer coating, or plastic coating, that we can put onto medical devices and we've been able to test it. We're able to reduce, in the lab, biofilm formation by up to 99 percent. So it's really exciting that we can see these results, and yeah we're really excited about this technology.

Chris - This works in clinically relevant bugs does it? The kinds of bacteria that cause urine infections, if you have a surface which is coated in your new material, those sorts of microbes can't gain a toehold.

Andrew - Yeah. So we were focused on the urinary catheter and so we were testing this particular polymer, we were testing it on the bacterial species associated with those infections, so things like e. coli, and on a bacteria called Proteus mirabilis. And we've tested it with these bacteria, and that's exactly the ones we were able to show a reduction in this biofilm formation.

Chris - What is the new material and how does it do this?

Andrew - So it's a synthetic polymer, so it's a plastic coating that we can put onto the medical device. The particular polymer that we are using has a special property which we call amphiphilic. So materials are usually either able to dissolve in water. We call that hydrophilic, or they prefer to dissolve in things like oil which you call hydrophobic. Our polymer actually is amphiphilic. So it's both water soluble and oil soluble. And this particular property is what is able to disrupt the bacteria's ability to form biofilm.

Chris - And is it actually any good at doing that? So if you if you make a surface with this, you said that it suppresses the numbers down, but it only takes one or two microbes to then trigger an infection. So if you actually do this clinically, have you got data showing that this protects patients?

Andrew - Yeah. So we've begun clinical testing in March, earlier this year. So we're still in early days of the actual clinical testing. We've tested it in about 100 people. The results look pretty good. It looks like we are reducing the amount of bacteria associated with the particular devices, and what we're really interested in doing is reducing the infection rate. If you have a catheter it's a 3 to 5 percent infection rate associated with using that device. And we'd really like to just be able to reduce those sorts of infection rates. But it looks really promising in the clinical trials we've done thus far.

Chris - And could you just very briefly could you translate this do you think, beyond the bottom end of the body, to plasticware and devices going into any part of the body? Because anything we put into the body; hip replacements, heart valves, whatever, is susceptible to infection by circulating microbes isn't it? Could you prevent that?

Andrew - Urinary catheters have really, the highest rate of infection of any medical devices. They’re the obvious place for us to start, but once you've been able to demonstrate efficacy, that it works with this particular device, then absolutely we would like to be able to explore other particular devices. We are particularly targeting preventing that biofilm formation. And so there's those devices such as endotracheal tubes where you get ventilator associated pneumonia, that sort of device is absolutely suitable for this material as well. And yes, in fact, all the medical devices.