Common Food Additive Linked with Increased Virulence of C difficile

Investigators from the Baylor College of Medicine in Houston, Texas, have discovered that a common food additive, trehalose (an artificial sugar frequently derived from mushrooms or seaweed), can be linked with the increase and severity of outbreaks involving 2 strains of Clostridium difficile (C. difficile).

In 2011, the US Centers for Disease Control and Prevention (CDC) reported that C. difficile was responsible for about half a million infections in the United States. Approximately 29,000 of those individuals died within 30 days of their diagnosis. Most infections are the result of exposure to the pathogen in the hospital and the use of antibiotics. There are multiple strains of C. difficile; however, in recent years, 2 strains have become increasingly dominant: RT027 and RT078.

“Our group and others have found that C. difficile lineages RT027 and RT078 have become dominant more recently around the globe,” first author James Collins, PhD, a postdoctoral in a press release on the study. “These lineages have been present in people for years without causing major outbreaks; in the 1980s, they were not epidemic or hypervirulent but after the year 2000 they began to predominate and cause major outbreaks. We wanted to know what had helped these lineages become a major health risk.”

It is already well-documented that the use of fluoroquinolones is a contributing factor to the increase in infections with RT027, as well as other strains of the pathogen. However, the investigators wanted to know if there are other factors at play as well. Therefore, they focused on the food source preferences for the 2 strains. What they found was the 2 strains could, “grow on levels of sugar trehalose that are about 1000 times lower than those needed by other lineages of these bacteria, giving RT027 and RT078 a major advantage. Each lineage is highly efficient at using trehalose and evolved independent mechanisms to utilize this sugar,” according to the press release.

To determine how this ability to metabolize low levels of trehalose could relate to an increase in the severity of disease, the investigators turned to a mouse model of C. difficile infection. According to Dr. Collins, for their study, “mice received a strain of the RT027 lineage of C. difficile and a diet with or without low trehalose levels. What the mice ate made a difference to the virulence of the infection; mortality was higher in the group consuming trehalose.” Interestingly, the investigators found that this increase in the severity of disease was not the result of a greater number of bacteria, but rather that the strain of C. difficile produced higher levels of toxins when given access to trehalose.

Speaking on these findings in the press release, Robert Britton, PhD, professor of molecular virology and microbiology and member of the Alkek Center for Metagenomics and Microbiome Research and the Dan L Duncan Comprehensive Cancer Center at Baylor College of Medicine stated, “In 2000, trehalose was approved as a food additive in the United States for a number of foods from sushi and vegetables to ice cream, and about 3 years later the reports of outbreaks with these lineages started to increase. Other factors may also contribute, but we think that trehalose is a key trigger.” Dr. Collins added, “Our study suggests that the effect of trehalose in the diet of patients in hospitals with RT027 and RT078 outbreaks should be further investigated.”