A plethora of skin bacteria

31 May 2009

Interview with 

Dr Julie Seagre, National Human Genome Research Institute


Chris -   Now also in the news this week, researchers have discovered a far more diverse collection of bacteria living on our skin than we thought was possible before, and it turns out that it's not just our good old friend Staph aureus, or other species of Staphylococcus that lay claim to our bodily surfaces.  To tell us a bit more, here is Julie Segre, hello Julie...

Julie Segre - Hello.

MRSAChris -   Welcome to the Naked Scientists.  You've published this wonderful paper in Science this week about this, how did you go about mapping what bugs were living on who and where?

Julie Segre -   Well it's really quite straightforward because the skin is so accessible, so we asked healthy volunteers to come in to the NIH clinical centre, and we took something that looks very much like a Q-tip and we swabbed the bacteria off the different parts of their body, everything from their forehead to behind their ear to behind their knees to underneath their foot and between their fingers, and then instead of culturing these in the lab, which has been our traditional method for knowing what bacteria reside on the skin, we sequenced the DNA immediately.  So there was no culturing, we just looked at the signature of each bacteria by it's DNA sequence, and those sequences are unique enough that we could say 'this is a staphylococcus, this is a streptococcus, this is a Corynebacterium', and we found an enormous diversity of bacteria that we really hadn't appreciated before.

Chris -   Because when you put things in culture, of course, there's a selection applied, in other words, some things won't grow in culture, so scientists will have missed them before, but by using genetic techniques, you're able to see what we couldn't see before.  How are you then going to take that further, what can you tell us about the spectrum of bugs that are on the body's surface and how they might be linked to various diseases, for instance?

A picture to illustrate pigmentation of human skin.Julie Segre -   Well this is a baseline, and studied that were done previously that were based on culture really gave us an incomplete view.  Now some of these bacteria, actually, now that we know we're looking for a Pseudomonas or we're now looking for a Corynebacterium, we can now culture them.  And the interesting thing about culturing bacteria is it's very hard to know what you don't know, but it's easy to find what you are looking for.  So now we tailor the media, for example a lot of the bacteria live on the oily surfaces of our skin, and when we add, we really just add lipids or oil to the culture broth, now we can grow these bacteria - we just didn't know they were there before.  This gives us a baseline so now we can begin to examine eczema, psoriasis, acne, we can begin to ask what is different?  Besides even what we can culture in the lab, how has the microflora changed, and then how do we have tailored therapies to being it back into balance?

Chris -   Because some people have suggested that some of those skin conditions that you cite are aggravated by the presence of bacteria, and that in fact they drive or stimulate the condition and make it worse.  It's not so much that it's just because there's damaged skin there, it's the combination of some damaged skin, which gets these bacteria in there in the first place, and then they make the problem worse.

Julie Segre -   That's absolutely right.  Something like eczema has a very strict connection with a Staphylococcus aureus infection.  Then there are other diseases like the MRSA, the Methicillin-resistant Staph aureus, we know that's a bacterial infection, but we also know that a lot of people have a small, tiny, tiny amount of MRSA that you could find in their nose - they never get an infection.  So we're suggesting that it might be the healthy bacteria, the commensals, that keep those pathogenic bacteria in check.

Chris -   I was just going to say, because, we have come around to the idea in recent years that having a healthy intestinal bug spectrum helps to protect us from various things, if you go to a foreign country and you don't get travellers' diarrhoea because you have a healthy microbial flora, could the same be true of the skin, and in fact people in whom there is some kind of problem with their normal skin bacteria, it makes them more prone to getting infections that a person who doesn't have that problem with their skin flora wouldn't get?

Julie Segre -   That's such an interesting idea to pursue, because its' interesting from the perspective of science, I think that's absolutely right on and that's where we're going to go with these experiments - to understand maybe why someone has a predilection for developing a skin disorder based on a change in their microflora.  It's also interesting from a societal perspective - why is it that we want to eat prebiotics and balance our gut microflora, but we want to sterilise the outside of our bodies?  We have to realise that there are healthy bacteria that live on our skin, and that we need to promote their growth.  I'm not talking about letting everything grow on your skin, there are a lot of transient bacteria that are bad, and I'm a deep believer in personal hygiene - washing your hands, using soap and all sorts of products.  I think there's a great use for all sorts of skincare products, but I also think that we have to realise that the goal is balance.

Chris -   I was just going to say, Julie, have you been in the shower this month?! No, I'm just joking, but basically the way forward now is to begin to say how do we tie different bacterial populations to different diseases or lack of diseases, can we understand more about what's healthy.  In the long run, perhaps we're going to see skin crèmes that are not designed to abolish bacteria, but to encourage the ones we do want, not the ones we don't.

Julie Segre -   Absolutely, and I think there are also intrinsic changes to our skin, the skin of a baby is not the skin of a teenager, is not the skin of an older person, so we have to understand that these things change with time, and that as we change the environment in which we live, we may be altering the microflora.  I think these are going to have profound effects on both common and rare skin disorders.

Chris -   Julie, we're going to have to leave it there, thank you very much for joining us.  

Julie Segre -   Thank you so much.

Chris -   That was Julie Seagre, who is from the National Human Genome Research Institute in the US, she's got a paper in Science this week in which she sets out basically what's living on you.


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