Is sugar behind the rise of a superbug?

Clostridium difficile is a bacterium commonly causing problems in hospital wards. It leads to diarrhoea and is now responsible for thousands of deaths each year. But it's only since the year 2000 that one strain, or ribotype, in particular has been spreading faster and becoming more dangerous. Antibiotic resistance is part of the problem, but now a new study has revealed that our diets may also be to blame. Georgia Mills heard from study author Robert Britton, professor of microbiology at Baylor College of Medicine...

Robert - We wanted to understand why they’re doing better in the environment so one of the things we tested was whether or not there were certains sugars or other types of carbon sources that ribotype 027 strains liked better than other C. difficile strains and we stumbled upon this disaccharide of glucose called trehalose. While we were testing this we found that ribotype 027 strains do much better on trehalose. But what was more surprising is we found a second ribotype - ribotype 078 - that could also eat low concentrations of this sugar and this ribotype is also an epidemic and hyper-virulent rybotype of C. diff. It was very striking that these two very unrelated ribotypes had both acquired this ability and both started causing major epidemics around the early 2000s.

Georgia - Do we know why that timing is important - why the early 2000s?

Robert - We investigated the mechanism for how trehalose was able to be eaten at lower concentrations in both these strains and they were completely independent. So what was the key driver of why these emerged in the early 2000s? What we think has happened is trehalose is a sugar which the food industry for a long time has wanted to use as a dietary additive but, unfortunately, it was very expensive to produce, and it cost 700 dollars a kilogram prior to the year 1995. A low cost production method was invented in that year that drove the price down to 2 to 3 dollars per kilogram, and that made it very attractive for the food industry to use. It was approved for use in the United States by the FDA in 2000 and in Europe in 2001. We think that’s the key link.

Georgia - Okay. So we’ve this evidence that these two very dangerous strains have both separately got this ability to break down this sugar, and it’s also the timing of the sugar becoming available in Europe and America coincides with when these started to become dangerous. But do we know for sure it is this sugar that’s causing it or could it be something else and it’s just a coincidence?

Robert - It is an association and there’s no way of going back and for sure proving this. We think that the tipping point for these two strains was really the addition trehalose. And the fact that we do see increased disease severity in our mouse model which is associated with what we see in humans is also a striking coincidence. We hypothesised that this is the case and we hope that this stimulates future clinical research to see if limiting trehalose in patients that have these types of c-diff in their intestines will improve their outcome.

Georgia - That was going to be my next question: where is trehalose found?

Robert - Trehalose is a sugar that’s found in many different products. Unfortunately, we don’t know exactly which because that level of description on our labels isn’t always there. But if you look at the generally regarded as safe report by the FDA, what we find is that it’s basically anywhere that you would put regular table sugar sucrose. You see it in standard things you’d imagine like ice cream and cakes and other candies, but you also find it in ground beef, pastas, bread, sushi. Things that you may not really think that there’s a lot of sugar in but, in fact, it is added. It’s hard to know exactly how much and where it is, but it clearly has inundated the market since it was approved.

Georgia - So not very easy or practical to cut it out of our diets then? What about in hospitals: is there anything practical we can take forward from this?

Robert - I think at this stage the research certainly suggests that we should do more research to see if limiting trehalose in hospitals will help drive the emergence of some of the ribotype 027 and 078 hyper virulent strains. And if we can also impact the health of patients that have this by altering their diet and not providing the sugars that make this disease more severe. I’m hoping that that’s where future research will go in the clinic...