A food additive responsible for the severity of some Clostridium difficile infections
A food additive, trehalose, is thought to be responsible for the severity of some Clostridium difficile infections, according to the authors of a study published in the prestigious journal Nature.
Two hypervirulent strains of Clostridium difficile were at the root of epidemics of serious intestinal infections which appeared in North America and Europe between 1995 and 2007. Resistant to the antibiotic used to eradicate them until then (fluoroquinolone), in a few years they became the major cause of C. difficile nosocomial infections in most countries of the world. But this antibiotic resistance does not explain the virulence of these strains, which are responsible for very severe cases. Other factors are thought to be involved, in particular the growing use of the sugar trehalose in the food industry.
Trehalose, a very widely used food additive
Trehalose was little used by the food industry before the 2000s as it was considered too expensive. However, improved production techniques reduced its cost and led manufacturers to include it as an additive in all kinds of products: sushi, ice cream, pastry, soups... According to the authors of the American study, the surge in hypervirulent C. difficile strains could be due to the capacity of the bacterium to use trehalose as a source of carbon. Analysis of the epidemic strains shows that they all possess the genetic mutations that enable them to metabolize trehalose, even when it is present in small quantities, and to produce more toxins–which would explain their greater virulence.
Small amounts are enough
Experiments conducted in mice infected by one of the two strains confirmed this hypothesis: they revealed a mortality rate in rodents that was three times higher when their food contained trehalose. The authors emphasized that there is no need to ingest massive amounts of the additive for a risk to appear: in humans, consumption of one ice cream allows a sufficient quantity of trehalose to reach the intestinal microbiota and enable the bacterium to grow. They consider that it is therefore the increase in the consumption of trehalose which has contributed to the emergence of hypervirulent strains of Clostridium difficile, the cause of the epidemics.
Collins et al. Dietary trehalose enhances virulence of epidemic Clostridium difficile. Nature doi:10.1038/nature25178