Recent research by UT Southwestern Medical Centre shows reduced susceptibility of mice fed with a plant-rich diet to gastrointestinal infections from harmful pathogens such as a currently widespread outbreak of E.coli associated with romaine lettuce which is under investigation. Enterohemorrhagic Escherichia coli, is one of the virulent strains of E.coli which causes the deadly inflammation in the colon with bloody diarrhea and vomiting, involved in many foodborne outbreaks throughout the world every year.
One of the professors of microbiology and biochemistry at UT Southwestern, Vanessa Sperandio, Ph.D., said there has been a lot of unsubstantiated information about a plant-based diet, whether it is better than typical Western diet, which has high amount of protein and oil and relatively low fruits and vegetables. So they decided to test it.
The study on the EHEC mouse model is published in the journal Nature Microbiology and is available online.
Plant-rich diet has high pectin content. Pectin is a gel-like substance found in different fruits and vegetables; it is digested into galacturonic acid by the gut microbiota, which n result inhibit EHEC virulence.
This is a concern of public health because outbreaks of EHEC can lead to hemorrhagic colitis which is very harmful and sometimes can cause death, specifically in the very young and the elder people.
Harmless strains of E.coli are one of the commensal microbes living in the human’s colon and that of other mammals, where they aid the host’s normal digestion metabolism.
The commensal microbes around the gut line act as a barrier for intestinal pathogens. EHEC and some other similar gram-negative microbes overcome this barrier displaying a secretion system T3SS. T3SSs are molecular syringes that inject a combination of virulence proteins into the host’s cells lining the colon, resulting in inflammation and other symptoms of inflammation. Sperandio said that the researchers used a similar pathogen, Citrobacter rodentium because the mice are unaffected by Enterohemorrhagic E. coli.
The study outcomes showed that good and pathogenic E.coli use different sugars for their nutrition. Also, the dietary pectin protects the pathway by which the pathogenic EHEC becomes more virulent.
Another different type of commensal gut microbes metabolize dietary pectin from vegetables and fruits into galacturonic acid which is a sugar acid, used by EHEC and C. rodentium in two ways. Initially, the sugar acid is used as an energy source but once it becomes depleted, the survival strategy is changed by the pathogens like a switch and instead of using it for nourishment the pathogen use it in a signaling pathway which increases EHEC’s and other virulence factors of similar microbes by using syringe-like T3SS.
Researchers fed pectin to mice and they bear infection for a week. The colons of six mice fed with a chow diet having 5 percent extra pectin and the colons of four mice with a typical diet were compared. The results showed a decreased rate of infection in mice fed pectin.
The researcher emphasized that this research is a key step to define the molecular mechanisms of the commensal gut species, which impact the pathogenesis of the intestinal pathogens. This will provide a better understanding of intestinal diseases and about the strategies for reducing the incidence of the symptoms caused by the harmful gram-negative pathogens, through advanced therapeutic drugs and new vaccines.