Maggots and MRSA
Chris - A very exciting discovery was announced this week from scientists who are at the University of Manchester, and they've been exploring the question of how to tackle the problem of MRSA, or Methicillin Resistant Staphylococcus Aureus. Speaking with Chris Smith is one of the scientists behind that work is Professor Andrew Boulton, and he joins us to talk about it now...
Andrew - Well I'm a clinician and we treat a lot of diabetic patients with foot ulcers as a consequence of loss of sensation and vascular disease they can injure their feet. They're often infected and we treat them with antibiotics, but after treatment with routine antibiotics it's not unusual to get resistant organisms colonising the wound. We have been using for the last ten years or so Maggot or, if you prefer, Larvae therapy to treat these wounds and we observed a couple of years ago that a number of the MRSA infected wounds seemed to be cleared of this contamination by treatment with the larvae.
Chris - Is MRSA a major problem now in the community, because traditionally this was something which we had bred in hospital by wide scale use of antibiotics, and largely it was a hospital problem. Are you saying it's very much a community problem; there are people out there in their homes with it?
Andrew - Sure. MRSA is everywhere, basically, it was more common in hospitals but much of the MRSA we see now is community acquired.
Chris - Presumably it's therefore a problem to get rid of; you can't just throw antibiotics at these patients, as it's MRSA it's very difficult to clear.
Andrew - Absolutely, these are very resistant organisms to a number of the more regularly used antibiotics. MRSA develops because we've knocked out most of the sensitive organisms, so the challenge is how to remove this, as we've already published a paper some years ago showing that those wounds that are contaminated with MRSA are slower to heal.
Chris - So what did you actually do in the study to exploit the maggots?Andrew - Well the first study we did was an observational treatment of consecutive patients with MRSA colonised wounds with larvae therapy. We apply about 100 sterile larvae of the greenbottle fly to the wound, these stay on for about 3-5 days, they go on the size of a small grain of rice and they come off about ten times larger, the sort of maggot you could use for fishing tackle. We used about three to five applications of these and of thirteen consecutive patients, twelve were completely cleared out of the MRSA.
Chris - Why is that? What are the maggots doing that antibiotics won't do?Andrew - Well that's what we're working with our microbiologist to see. It does appear that the maggot is a bit like a magnet if you imagine the MRSA as iron filings, it appears to be attracted to the cuticle. We're also dissecting out larvae removed from wounds to see if they ingest them and we're looking at a number of possibilities to see if the substances they secrete, for example, kill off or at least stop reproduction of the bacteria.
Chris - So in other words the maggots' digestive juices (which they're squirting onto the tissue that they want to eat) are in some way also toxic to the bugs?Andrew - That's possible; it's been known for some time that these may have bacterial killing property. Of course the idea would be to take this further, to try and extract whatever it is that is active in the maggot that is killing the MRSA and perhaps to develop a treatment that doesn't require live maggots.
Chris - How did the patients feel about this, when you said to them "would you like us to fill your wound with maggots"?
Andrew - We don't quite say it just as you did, we explain that these have been used, literally for hundred of years in wound healing, and that they're bred in a sterile nature so they won't cause any problems. Most of our patients have nerve damage so they have no sensation in these wounds, so they're not aware of the larvae and the fact is that these really do remove and digest dead and necrotic tissue as well as infection so they're very good at cleaning wounds to allow healing to follow afterwards.
Chris - And when people do get the sensation of maggots in the wound, what do they say it feels like?
Andrew - Sometimes they're aware of a tickle, or 'pins and needles', or sometimes aware of minor movement, but it's difficult to know how accurate that description is, or if it is that they know that the maggots are there. Chris - So presumably now you would like to try this in not just diabetics but people with all kinds of wounds, and see if you have something which can attack MRSA in an effective way?
Andrew - Absolutely. I'm a diabetes specialist so we now have a grant to do a proper trial because this is suggestive and not proof. In medicine we need absolute proof from a randomised control trial so we're about to start a trial where we randomise patients to either have Larvae therapy or another, more conventional treatment, to confirm our initial observations.