Hospital ‘superbug’ colonizes colon

U. MONASH (US) — A mutation turns a common hospital bacterium into a deadly superbug that kills increasing numbers of hospital patients worldwide.

The superbug accounts for an estimated $3.2 billion each year in health care costs in the United States alone.

In research published in the open-access journal PLoS Pathogens, Dena Lyras and Glen Carter of Monash University demonstrate how a naturally occurring mutation in the bacterium Clostridium difficile causes potentially life-threatening diarrhea in hospital patients undergoing antibiotic therapy.


Lyras says C. difficile, which is able to colonize the colon when antibiotics have wiped out protective bacteria in the gut, causes a range of bowel disease symptoms, from mild diarrhea to more chronic forms.

“We’ve found that particularly dangerous strains of C. difficile are produced when a mutation effectively wipes out an inbuilt disease regulator, called anti-sigma factor TcdC. Not only are these strains hypervirulent, they are resistant to broad spectrum antibiotics, making them difficult to treat,” says Lyras.

The results of the study suggest that all C. difficile strains carrying a similar mutation have the inherent potential to increase toxin production and become hypervirulent.

“Over the past decade, there has been an astonishing increase in C. difficile infections throughout the world. Worryingly, the bacteria are also infecting people previously considered not at risk, including children and pregnant women,” says Lyras.

“This is a major public health issue. Hospitals, intended as places of healing, provide the perfect environment for the rapid evolution of pathogens that target susceptible patients.

“We must understand how these superbugs develop so we can develop treatments to combat them,” adds Carter.

“This study gives us a better understanding of these strains—how they develop, how they cause disease, and why they are so harmful—so we can design new strategies to prevent, control and treat the rising rates of infection.”

The Monash team collaborated with scientists from the University of Glasgow, Kansas State University, and Institute Pasteur. The researchers were funded by the National Health and Medical Research Council, Australian Research Council, Wellcome Trust, and National Institutes of Health.

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