Texas A&M researcher working to stop superbug that CDC calls healthcare system threat

Published: Dec. 15, 2021 at 1:28 AM CST
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COLLEGE STATION, Texas (KBTX) - A Texas A&M researcher is working on stopping a deadly superbug that the CDC has designated as one of the five most urgent threats to the U.S. healthcare system.

The superbug is called C. difficile, and it can cause serious diarrhea. Patients usually come down with a C. diff infection while they’re in the hospital getting treatment for other ailments. This particular superbug causes more than 500,000 infections per year, 29,000 of which result in death.

Superbugs are bacteria that are multidrug resistant, and therefore antibiotics are generally ineffective in fighting them.

“Given that these antibiotics don’t just target the one infectious bacteria that you want, they have broad spectrum activity,” Texas A&M Department of Biology Professor Joe Sorg said. “What they do is disrupt the normal good bacteria you have in your gut, and then that makes you susceptible to a C. diff infection. It becomes difficult to treat given that antibiotics are then used to treat C. diff, which then becomes a problem of making you susceptible to C. diff again, so you just get this cycle of recurring infections.”

Sorg’s work was interested in looking at what components of the microbiome lead to protection against C. diff invasion. The research done by Sorg and one of his graduate students, Andrea Martinez Aguirre, found C. difficile shares a food source with other metabolites in the gut.

”They happen to consume the same food that C. diff really wants to eat, and the food is two amino acids, proline and glycine, present in everybody’s diet,” Sorg said. “If you can remove the food source, C. diff can’t gain a hold in the gut and cause disease. What we think is the really interesting part is that once C. diff does come in and cause disease, it also consumes that food, leading to the microbiome not being able to regenerate to cause protection. It’s like this microbial metabolic warfare, if you will.”

This differs from what was originally believed about how the body protects against the superbug.

“Historically, or at least for the last decade, it was thought that the microbiome produces toxic metabolites and these secondary bile acids,” Sorg said. “They take a molecule that you make, and they spit out a toxic version of it. It was thought that’s the way that the microbiome protects against C. diff.”

Sorg says there are a lot of different areas where C. diff comes into contact with bile acids. For this project, they wanted to understand if it’s the toxic metabolite generated by the microbes that exclude the superbug.

“To answer that question, we used a mutant mouse that can’t make one of the predominant bile acids. Because the mouse can’t make it, the healthy bacteria can’t consume it and spit out the toxic metabolite,” Sorg said. “We rederived this mutant mouse germ-free so that we can then fine tune the bacteria that we give to it to understand if it’s actually the secondary bile acid that is toxic to C. diff.”

Sorg says their next step in fighting the superbug is figuring out how to ensure only the good bacteria in the gut eats that food source and preventing C. diff from consuming it.

“We’re trying to get around this by rational design of either narrow-spectrum antibiotics or probiotics,” Sorg said. “That’s kind of where we are right now with the probiotics, trying to identify those consortia of bacteria that can provide really, really effective protection against C. diff, and that’s still kind of in its infancy.”

Sorg says one very effective treatment for patients with C. diff infections is a fecal microbial therapy, or FMT. Although it is still considered an experimental treatment, Sorg says it is widely used and approximately 90-95% curative.

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