Stress May Encourage E. Coli Illness

WEDNESDAY March 18, 2009 -- Researchers say they have found a possible link between stress-induced sickness and a diarrhea-causing strain of the E. coli bacterium.

Researchers at the University of Texas Southwestern Medical Center say the newly discovered QseE receptor, found on the enterohemorrhagic Escherichia coli (EHEC) strain, picks up signals when stress hormones are released in the body. Once activated, this pathogen -- which usually enters the body through contaminated food such as raw meat -- sets off a series of reactions that release toxins into the body. This process changes the makeup of other cells and robs the body of nutrients.

"The bacteria get what they want -- nourishment -- and the person ends up getting diarrhea," study senior author Vanessa Sperandio, UT Southwestern associate professor of microbiology, said in a news release issued by the school.

QseE, which is found only in intestinal bacteria, works with the known previously found QseC sensor kinase (enzyme) on the EHEC bacterium. QseC, discovered by Sperandio's lab about three years ago, provides the timing for the bacterium's actions, including the regulation of the genes necessary for EHEC to cause diarrhea. It appears to have a key role in other disease development because its senses stress cues, mostly from body chemicals generally linked to blood poisoning, also known as sepsis.

"Patients with high levels of phosphate in the intestine have a much higher probability of developing sepsis due to systemic infection by intestinal bacteria," Sperandio said. "If we can find out how bacteria sense these cues, then we can try to interfere in the process and prevent infection."

The findings were published online March 10 and are scheduled to be published in a future print issue of the Proceedings of the National Academy of Sciences.

The human body usually hosts millions of potentially harmful bacteria that stay dormant until they receive a signal that it's to release their toxins. If those signals never arrive, the bacteria pass through the body without harm.

"There's obviously a lot of chemical signaling between host and bacteria going on, and we have very little information about which bacteria receptors recognize the host and vice-versa," Sperandio said. "We're scratching at the tip of the iceberg on our knowledge of this."

In previous research, Sperandio discovered that phentolamine, an alpha blocker used to treat high blood pressure, and a new drug called LED209, prevent QseC from doing its nasty work. Tests on whether phentolamine also works on QseE are expected to follow.

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more about bacteria and foodborne illness.

Posted: March 2009


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