Bacterial discovery could lead to a vaccine for traveler’s diarrhea

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Photo Credit: Alekka Hernandez | Daily Texan Staff

A new bacterial discovery by UT researchers could help you spend more of your vacations hitting the beach instead of the toilet.

 

UT and the Naval Medical Research Center collaborated to investigate how the bacteria ETEC, a form of E. coli and the most common cause of traveler’s diarrhea, functions inside of the human body. They found that ETEC releases toxins based on oxygen levels in its surrounding environment.

 

Lead researcher Alex Crofts, a former UT graduate student and current researcher at the Scripps Research Institute, said this is the first time oxygen levels have been associated with virulence factor expression, or the creation of toxins, in ETEC.

“It’s not new that oxygen can influence virulence factor expression,” Crofts said. “It definitely happens in other bacteria, but this is the first time we’ve seen it in ETEC.”

According to the paper published by Crofts and other researchers in the Proceedings of the National Academy of Sciences, ETEC uses a protein called FNR to sense environmental oxygen and release toxins during infection.

FNR is a very common way bacteria use to sense different levels of oxygen, Crofts said.

For instance, when bacteria are outside of the human body, there’s plenty of oxygen in the atmosphere, but when bacteria enter our bodies, there are often lower levels of oxygen. Bacteria use FNR to switch between these two types of environments, Crofts said.

“It’s kind of interesting that this fundamental factor, FNR, is involved in something that’s so basic as trying to grow in different oxygen levels but can also contribute to disease,” Crofts said.

Crofts added this discovery could lead to the development of a vaccine for traveler’s diarrhea.

“One of the most important things for making a vaccine is having a particular part of the bacteria to target,” Crofts said. “The vaccine trains your immune system to fight off the bacteria.”

Knowing that oxygen influences toxin release in ETEC gives scientists a new pool of oxygen-sensitive genes they can choose from to find a good candidate for the vaccine, Crofts added.

Crofts said he hopes with the new oxygen-specific profile, scientists can target oxygen-sensitive genes for the vaccine instead of adhesins, or molecules that allow bacteria to attach to host cells and later infect them.

Adhesins are currently the most advanced candidate for ETEC vaccine targets, according to an article published in the journal, Vaccine.

Vaccines that target one specific adhesin will not protect against all strains, because there are many different strains of ETEC with slightly different versions of the same adhesin, Crofts added.

He said studying the genes linked to oxygen-sensing instead of specific adhesins could be a more effective way to develop a vaccine.

A vaccine for traveler’s diarrhea would be an important way to protect travelers, Crofts said.

“Sometimes you spend a lot of money to travel to a different country, and then as soon you get there you get sick because you drank something that was contaminated with bacteria,” Crofts said. “What we found is one of the most common bacteria that causes traveler’s diarrhea senses oxygen in the environment to make you sick … now that we know that’s how it can make you sick, we can target that with the new vaccine.”