Plant-rich diet may protect against foodborne infection

In a new study, researchers found a plant-rich diet may help prevent gastrointestinal (GI) infection from a pathogen such as the one currently under investigation for a widespread E. coli outbreak tied to romaine lettuce.

The research was conducted by a team at UT Southwestern.

A strain of E. coli known as EHEC, which causes debilitating and potentially deadly inflammation in the colon with symptoms such as bloody diarrhea and vomiting, is implicated in several foodborne outbreaks worldwide each year.

There has been a lot of hearsay about whether a plant-based diet is better for intestinal health than a typical Western diet, which is higher in oils and protein but relatively low in fruits and vegetables.

Plant-rich diets are high in pectin, a gel-like substance found in many fruits and vegetables.

Pectin is digested by the gut microbiota into galacturonic acid, which we find can inhibit the virulence of EHEC.

According to the team, intestinal pathogens like EHEC sense the complex chemistry inside the GI tract to compete with the gut’s resident microbiota to establish a foothold.

Over centuries, the pathogens have developed different strategies to compete against the so-called good, or commensal, microbes that normally line the gut.

Those commensals include harmless strains of E. coli living in the colons of humans and other mammals, where they help the host’s normal digestion process.

The word commensal means “eating at the same table” and that is what the symbiotic bacteria that make up the gut’s microbiota do.

The commensals that line the gut present a significant barrier to intestinal pathogens. EHEC and similar gram-negative bugs overcome that barrier by deploying a secretion system called T3SS.

In the study, the team found that the good E. coli and the pathogenic ones like EHEC use different sugars as nutrients.

They also found that dietary pectin protects against the pathway the pathogenic EHEC uses to become more virulent.

The team says that a pectin level of 5 percent appears to prevent the pathogen from activating its virulence repertoire.

She stresses that the research is one step in a journey to define the molecular mechanisms that govern how the commensal species in the gut impact the virulence of intestinal pathogens.

One author of the study is Vanessa Sperandio, Ph.D., professor of microbiology and biochemistry at UT Southwestern.

The study is published in Nature Microbiology.

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