How antibiotics open door to “bad” gut bacteria: more oxygen

By Carole Gan

Antibiotics are essential for fighting bacterial infection, but they can also make the body more prone to infection and diarrhea. Exactly how do antibiotics foster growth of disease-causing microbes – and how can resident “good” microbes in the gut protect against pathogens, such as Salmonella?

Now research led by Andreas Bäumler, professor of medical immunology and microbiology at UC Davis Health System, has identified the chain of events that occur within the gut lumen of mice after antibiotic treatment that allow “bad” bugs to flourish.

This has profound implications, expanding the current view of how microbes interact with each other at the gut surface, wrote the authors of an accompanying commentary that appeared online with the study April 13 in the journal Cell Host Microbe. It could lead to new strategies to prevent side effects of antibiotic treatment.

According to Bäumler, the process begins with antibiotics depleting “good” bacteria in the gut, including those that breakdown fiber from vegetables to create butyrate, an essential organic acid that cells lining the large intestine need as an energy source to absorb water. The reduced ability to metabolize fiber prevents these cells from consuming oxygen, increasing oxygen levels in the gut lumen that favor the growth of Salmonella.

Less fiber breakdown by bacteria, more oxygen

“Unlike Clostridia and other beneficial microbes in the gut, which grow anaerobically, or in the complete absence of oxygen, Salmonella flourished in the newly created oxygen-rich micro environment after antibiotic treatment,” Bäumler said. “In essence, antibiotics enabled pathogens in the gut to breathe.”

Other research has linked low levels of butyrate-producing microbes with inflammatory bowel disease, but additional research is needed to determine if these findings are limited to butyrate and growth of Salmonella or if similar mechanisms underlie interactions that influence human health.

Other authors on the research paper include Fabian Rivera-Chavez, Lillian F. Zhang, Franziska Faber, Christopher A. Lopez, Mariana X. Byndloss, Erin E. Olsan, Eric M. Velazquez, Gege Xu and Carlito B. Lebrilla, all of UC Davis; and Sebastian E. Winter at the University of Texas Southwestern Medical Center.

The research study is entitled, “Depletion of Butyrate-Producing Clostridia from the Gut Microbiota Drives an Aerobic Luminal Expansion of Salmonella.” It was supported by Public Health Service grants AI096528 (A.J.B.), AI112949 (A.J.B.), AI103248 (S.E.W.), AI112241 (C.A.L.), OD010931 (E.M.V.) and AI060555 (E.M.V. and F.R.-C).

More information: A version of this story is also available here.

Carole Gan writes about basic sciences for UC Davis Health System Public Affairs.

2 responses to “How antibiotics open door to “bad” gut bacteria: more oxygen

  1. Gut bacteria are an important component of the microbiota ecosystem in the human gut, which has played an important role in human health, such as supplying essential nutrients. Such related antibiotics could focus more on the practical function.

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