New catheter material to prevent infections

Up to one in five hospitalised patients ends up needing a urinary catheter at some point, and with that comes a considerable risk of infection that prolongs hospital stays, drives up healthcare costs and can even be life threatening. Now a team at Nottingham University have discovered a new material that we might be able to use to coat catheters and possibly other medical instruments to prevent infection-causing bacteria from latching on and causing infection in the first place. Andrew Hook…

Andrew - This is a big problem for the NHS. It costs them about 2 billion a year to treat this biofilm. In fact, about 75 to 80% of hospital acquired infections are associated with catheters particularly as well. And so, we are really interested in trying to prevent bacterial infections associated with the use of urinary catheters.

Chris - Is that through making those devices harder for the microbes to gain a toehold on in the first place? Or is it through making them poison the microbes so that they don't gain a toe hold? Or both?

Andrew - Both approaches are used. So we try to poison or kill the bacteria. Actually this is the approach that people originally took, but hasn't shown any clinical efficacy. It doesn't work in hospitals. And so our approach was to stop the bacteria trying to, as you said, get a toe hold or particularly to form biofilm, which is this defense mechanism that bacteria have where they form a community. I kind of think of this as the same way that you might see buffalo out in Africa, they form a cluster that prevents the lions from being able to attack, and that's exactly what biofilms do where the immune system can't attack them. But our coating stops the bacteria from being able to do that and allows the immune system to clear them out.

Chris - Tell us about the coating then. What have you actually discovered?

Andrew - We've actually been working at trying to produce a coating that prevents the biofilm for a while. There's a few strategies that the bacteria can use to cause infection. So ones biofilm, which I've talked about. Another one is bacteria and particularly a species called Proteus mirabilis is able to do this swarming where it forms this raft of bacteria, which is able to travel up the catheter to the bladder and cause an infection. And so we'd already actually found a solution to the biofilm, but we hadn't found a solution to the swarming. We've been trying to do that and we ended up finding a polymer that can prevent the swarming but then couldn't prevent the biofilm. In this work, we've been able to combine those two together to develop a coating, which is able to address all the problems and overcome all the strategies that bacteria used to cause infection. So we can prevent biofilm, we can prevent swarming.

Chris - So under normal circumstances, quite a high fraction of patients in hospital will at some point need a catheter put in to drain urine. And because we've got something connecting the outside world to the inside, that is a superhighway for microbes to crawl up. And you are saying you have erected a roadblock that would give the M6 a run for its money that stops them getting in because they get hold of it.

Andrew - Yeah, exactly. They can't get in and then they can't get a foothold there. And it's a case of patients who do have catheters, there's a 3% chance of them developing an infection and that's cumulative. So after two days at 6%, three days, 9% goes up. After 30 days almost a hundred percent of patients get infections. And so yeah, we really think that we are causing a real, as you say, roadblock of bacteria being able to do that.

Chris - Those are big numbers, aren't they? How have you done this then? How did you find the right recipe for something that would work as a catheter but will deter microbes in this way?

Andrew - We accepted the fact that we don't actually understand how bacteria interact with materials, and so we couldn't really design a coating just from our understanding. And so we've used a high throughput approach where we try to screen as many different things as we can and then identify the ones that work. And so that's what we've been able to do. So we have this high throughput screen approach. We screen, hundreds in fact, thousands of different materials. We're able to quickly find the ones that work.

Chris - How good is what you found?

Andrew - Yeah, we're really pleased that we're able to produce a coating that is able to really get around all the different strategies that bacteria have. And particularly in the case of the swarming and preventing the really rapid bacterial movement, there really isn't another strategy that exists. And so we are really excited that we are able to find that. So we reduce the bacterial biofilm formation 99%. So we see a 99% reduction. And I think the bacteria that remain are still in this single bacteria form. So they get cleaned up by the immune system really well, which is really great. We're really excited. That has translated to clinical success as well. We are able to see a reduction in infection clinically, which is really exciting.

Chris - I thought microbiologists were very used to talking in terms of killing 99.9% of bacteria, but I'll settle for 99% in the meantime. You mentioned that one of the reasons why you took the approach, you did just brute force, try lots of chemicals until you find one that's a good hit. Does the fact you've now found one mean that we've now got a new avenue to explore understanding how it's doing that, which might give us clues as to how the bacteria do or don't traverse various surfaces and that might open the door to other treatments?

Andrew - Yeah, absolutely. I think that's a really good point. You know, we started from a position of not understanding the bacteria and the way that they interact with materials. And now we've done all these tests actually, we can use that to try and help ourselves understand the way that bacteria interact and then be able to engineer and design materials that actually work even better than the ones that we've found. So that is certainly a part of what we are trying to do. I think we've been able to identify a new class of materials with antibacterial properties and I think can really use that information to try and engineer even better performing materials.