Bacteria: What lies beneath

28 August 2018

Interview with 

Claire Bryant, University of Cambridge

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Gut Bugs

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You're going to need a cleaner boat. Chris Smith and Georgia Mills pick up vetenary scientist Claire Bryant, who warns them about the nasty bacteria lurking in the river, and discusses her own research into salmonella. But first, why do maiden voyages often smash bottles of champagne?

Clare - Yes. There’s really interesting history to boat launching which goes back thousands of years. The Greeks did it, obviously, to wish good luck on the boat because sailors are a suspicious lot. They used to do this with laurel wreaths and stuff like that.

And then through the middle ages it acquired a kind of religious connotation and at that time what they used to do is they used to drink a bit and then throw the residual on the boat, and then they chucked the vessel into the water. But that became very expensive because a lot of these vessels were made of precious metal.

It then morphed on over time into being a bottle of something to drink. And then ultimately, in the Victorian era I think, they actually started to use champagne. But it does present some challenges because the bottles have to be very very strong because the gas is under high pressure so the glass is actually very thick. So if you want to smash a bottle of wine against a boat and get it to break first time you have to score the glass to weaken it so that then when you smash the glass against the boat it will burst.

Chris - There have been some mishaps then where people have tried to launch ships and the bottle hasn't broken?

Clare - Correct. Yes, yes.

Chris - Oh my goodness! What do they do then then, because that’s bad luck isn’t it?

Clare - Well, they just have another go I believe. But I have seen some videos on YouTube where this is indeed the case.

Chris - So people would actually scratch the side of the bottle to put a weak point in?

Clare - Yeah. And the when you smash it against the ship it will burst.

Chris - Are you enjoying your champagne?

Clare - I am enjoying my champagne. I always enjoy a glass of champagne, Chris.

Chris - I’m only asking because Alex rinsed the glass out in the river.

Clare - Oh, thank you Alex. Now I will stop drinking it.

Chris - Because that was a horrible link to the fact that you are actually an immunologists. So ostensibly, the reason we asked you onto the punt was to talk about your science. What do you actually work on immunologically?

Clare - I work on salmonella bacteria which causes food poisoning and are a massive zoonotic disease. So by a zoonotic disease I mean one which jumps from animals into humans. As I work at a vet school I am particularly interested in bacteria such as salmonella which remain hidden basically. The immune system doesn’t seem to recognise them in animals, but as soon as you eat some chicken then the salmonella is then recognised by humans and gives you a nasty gut upset.

Chris - How does it actually make us unwell when we catch salmonella?

Clare - That’s quite a complicated process. With respect to the salmonella that jump from chickens into people, what they do is they produce a whole series of bacterial proteins which then invade the epithelial cell, which is the cells lining the gut and that then causes the cell to become inflamed, diseased, and causes diarrhea. So it’s quite nasty and it can, in certain circumstances, actually go across the gut and go into the blood supply and then people can get very sick indeed.

Chris - And you’re trying to work out, what, how the bacteria evade the immune system, or the immune system attack the bacteria?

Clare - There’s two things were trying to do. One is we’re trying to understand how salmonella activates the immune system in people. And then secondarily, we’re trying to understand why in animals like chickens, they don’t seem to see the salmonella in the same way. So what is it that’s different either about the bacterium or about the host animal, and the host animal’s immune system that means that salmonella can sit quite happily in a chicken gut and not cause any problems at all.

Chris - So the chicken is carrying the salmonella bacterium but it’s not making the chicken ill but equally, the chicken is not fighting off the salmonella and getting rid of it?

Clare - Yep, that’s absolutely right. One of the concepts we have is is there some way that we can remove the bacteria from the chicken by a vaccine process for example. Or by stimulating the immune system in the gut such that the bacteria, the salmonella that are present in the chicken gut are then got rid of and then they’re not available to go down the food chain and infect people.

Chris - How are you trying to do it?

Clare - Well, we’re trying to develop vaccines and we’re trying to develop immunostimulants that would actually do that. But in order to be able to target that in the most correct way, and trying to understand how the chicken sees the salmonella to then see which of the molecules that are best to target to see if we can then prevent the salmonella from sitting in the chicken gut, and sitting in the gut mucosal surface.

To understand how to tackle the problem, we need to understand the biology and the host immune interaction which, as yet, we don’t fully understand. But it’s kind of groovy. There’s lots of really interesting different differences between chickens and people in their immune system.

Chris - I’ve noticed one or two. They’re birds and we're humans. But is in the same way that I’ve got lots and lots of friendly bacteria living in my intestine and so my body tolerates them and doesn’t get rid of them because they do a good service for me. Is it that in a chicken salmonella bacteria behave like that and they’re almost like a normal part of the bugs that live in a chicken?

Clare - Effectively yes. But what we don’t understand is why that is. There are, for example, some salmonella that humans tolerate and don’t cause disease. There are some salmonella species that cause disease in chickens and there are other salmonella species that don’t, and there’s obviously complex differences in the salmonella genome which contributes to part of this. But, presumably, there are some molecules that are particularly causing pathogen effects in chickens that are present in some bacterial species and not in others and those are then different in the bacterial species that causes disease in humans. So it’s understanding the reason why one salmonella is a pathogen and another is a commensal is really of top top interest and I don’t think we’re really close to understanding that yet.

Georgia - While we’re talking about bacteria, as someone who takes semi-frequent dips in the Cam in the nice weather how worried should I be?

Clare - Very worried! The Cam is one of the area that hosts a bacterium called Leptospirosis, which can cause a disease called Weil's Disease. It’s really nasty so -you’re going to like this - it comes from rat’s urine. It’s carried by rats and dogs. We vaccinate our dogs against this disease specifically to prevent people getting Leptospirosis. It’s really nasty. You won’t catch me going in that river.

Georgia - Just asking for a friend - what are the symptoms?

Clare - There are a variety of symptoms. There are a variety of symptoms; at its most severe it can cause renal disease  - kidney failure; it can cause meningitis; it can cause severe fevers. At its mildest it would just cause you a severe fever and make you generally feel unwell. It’s not a bacterium you want to try and acquire.

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