The increasing frequency and severity of healthcare-associated outbreaks of C. difficile have been linked to trehalose.
Robert Britton, PhD
According to new research, the increasing frequency of healthcare-associated outbreaks of Clostridium difficile (C. difficile) have been linked to the commonly used food additive, trehalose.
The study, published in Nature, found 2 genetically distinct strains of C. difficile that have been present for years and after 2000 began to dominate and cause major outbreaks: RT027 and RT078.
Resistance to fluoroquinolone antibiotics is likely a factor contributing to the increase of RT027 infections, however it’s also a characteristic of other C. difficile lineages that are not epidemic. Researchers investigated other factors that could play a role in the increase of their virulence, primarily their food source preferences.
The 2 strains grow on levels of trehalose that are about 1,000 times lower than those needed by other strains of these bacteria, allowing for a major advantage.
The strains have independently acquired unique means to metabolize low concentrations of the disaccharide trehalose.
To determine the relationship of the increase in the severity of C. difficile and the ability to metabolize low levels of trehalose, researchers studied a mouse model.
In the study, mice received a strain of the RT027 lineage of C. difficile and a diet with or without low trehalose levels. The diet the mice consumed made a difference to the virulence of the infection, as mortality was higher in the group that consumed the sugar.
Researchers showed that trehalose enhances the severity of the infection in a manner that requires C. difficile to metabolize trehalose in mice. The sugar is present in the distal intestine of mice and humans in concentrations that the RT027 strain can metabolize.
Other experiments showed that the increase of the disease severity was not due to the result of a greater number of bacteria, but instead the specific strain produced higher levels of toxins when given trehalose.
“This changes how we think about hypervirulent C. difficile in that most studies have focused on virulence mechanisms for the rise of epidemic ribotypes of C. difficile emerging in the clinic,” Robert Britton, PhD, professor, molecular virology and microbiology, Baylor College of Medicine, told MD Magazine.
Since the RT027 and RT078 strains were present in clinics at least 10—20 years prior to becoming epidemic isolates, investigators examined where individuals would acquire trehalose in the diet.
In 2000, the US Food and Drug Administration (FDA) approved the sugar for human consumption, and the amount of trehalose predicted to be consumed once released on the market would vastly increase what people received naturally from the diet. The data support that the 2 ribotypes increased in prevalence because of the change in human diet.
“We were able to show, using a combination of in-vitro gut models and mouse models of C. difficile infection, that trehalose can promote disease severity of C. difficile infection and yield a competitive advantage for growth in a complex microbial community,” Britton added. “The link to RT027 and RT078 emergence in the early 2000s is the approval of use of trehalose in the US, which directly preceded the emergence of RT027 strains in North America. There of course is no way to show cause effect in humans, but the fact that 2 very different ribotypes (not closely related) of C. difficile became epidemic at the same time a sugar they can eat much better than other C. difficile ribotypes is a strong association.”
The effect of trehalose in the diet of those in hospitals with RT027 and RT078 strains of C. difficile outbreaks should be further investigated.
“We think that, while trehalose may have many beneficial properties for humans and the food industry, in this case the addition of trehalose to the human diet selected for these hypervirulent epidemic ribotypes of C. difficile,” Britton added. “Other factors may also contribute, but we think that trehalose is a key trigger.”