Here's why the epidemic strain of C. difficile is so deadly—and a way to stop it

August 1, 2016, University of Virginia
Study co-authors Stacey Burgess and Mahmoud Saleh and lead author Carrie Cowardin in the Petri lab at the University of Virginia School of Medicine. Dr. Cowardin led the team that discovered that the strain of C. difficile causing the current epidemic kills a key white blood cell whose role is to protect the gut from infection. Credit: Courtesy Bill Petri, University of Virginia School of Medicine

A new, epidemic strain of C. difficile is proving alarmingly deadly, and new research from the University of Virginia School of Medicine not only explains why but also suggests a way to stop it.

Until now, scientists have not understood what made this strain worse than other of the bacteria, the most common cause of hospital-acquired infections. The new strain kills up to 15 percent of infected patients, including those who receive antibiotics, and has become increasingly common over the last 15 years. This has prompted the federal Centers for Disease Control and Prevention to label it an "urgent threat."

A Potent Toxin

The finding comes from the lab of Bill Petri, MD, PhD, chief of UVA's Division of Infectious Diseases and International Health, and a team of international collaborators. PhD student Carrie A. Cowardin was working in Petri's lab when she discovered the diabolical mechanisms this strain of C. diff uses to overcome the body's natural defenses.

The strain is so deadly because it produces a toxin that kills protective cells, called eosinophils, found in the gut, Cowardin found. By destroying the gut's natural barrier, the bacteria can spread inflammation throughout the body. "We think that this toxin makes disease more severe by killing beneficial eosinophils, which seem to play an important role in promoting a healthy during C. difficile infection. When the eosinophils were depleted with an antibody or by the toxin, we saw dramatically increased inflammation. Restoring eosinophils by transferring them from a mouse that cannot recognize the toxin prevented the damage inflicted by the epidemic strain," said Cowardin, now a postdoctoral fellow at Washington University in St. Louis. "This builds on previous work in our lab showing that are beneficial and suggests that one reason this strain causes such severe disease is due to its ability to kill these cells."

Further, Cowardin discovered exactly how the toxin works, and how well it functions in this role. The toxin, she determined, requires a particular human protein that recognizes bacteria, a protein that plays a key role in the immune response. In short, C. diff is subverting the body's natural defenses to overcome those defenses.

This understanding of the 's action could be of great importance, as blocking it can rescue the protective cells in the gut. And that approach could lead to a new treatment to stop this of C. diff in its tracks.

"Nearly every day that I care for patients I am faced with this potentially deadly infection," Petri said. "Carrie Cowardin's discovery of why this strain of C. diff is so dangerous, and most importantly how to combat it, is a huge and most needed advance."

Explore further: Allergy-causing 'bad guy' cells unexpectedly prove life-saving in C. difficile

More information: Carrie A. Cowardin et al, The binary toxin CDT enhances Clostridium difficile virulence by suppressing protective colonic eosinophilia, Nature Microbiology (2016). DOI: 10.1038/nmicrobiol.2016.108

Related Stories

The answer to tackling superbugs could be more superbugs

May 11, 2015

Hard-to-kill bacteria or "superbugs" have become a major problem for hospitals. Between 5% and 12% of hospital patients in the EU are thought to acquire an infection during their stay, with many caused by bacteria such as ...

What makes C-Diff superbug deadly?

March 1, 2009

A major breakthrough about the potentially deadly superbug Clostridium difficile (C-diff) could lead to new ways to combat the bacterium, according to a study to be published March 1 in the journal Nature.

Recommended for you

'Pest-controlling' bats could help save rainforests

December 11, 2018

A new study shows that several species of bats are giving Madagascar's rice farmers a vital pest control service by feasting on plagues of insects. And this, a zoologist at the University of Cambridge believes, can ease the ...

The source of stem cells points to two proteins

December 11, 2018

Mammalian embryos are unlike those of any other organism as they must grow within the mother's body. While other animal embryos grow outside the mother, their embryonic cells can get right to work accepting assignments, such ...

The food poisoning find that could save lives

December 11, 2018

Researchers at The Australian National University (ANU) have made a discovery that has the potential to save lives when treating bacterial infections, especially serious food poisoning.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.