Gut Bug Gets Deadlier

New Strain of C. diff Doubles Bacterium's Deadliness; Hospitalizations Up

Medically Reviewed by Louise Chang, MD on May 28, 2008
From the WebMD Archives

May 28, 2008 -- A virulent new strain of the gut bug C. diff is sweeping the U.S. Among those who fall ill, the fatality rate has doubled to 2.2%.

A new study shows that diagnosed adult cases of C. diff more than doubled in five years: from 134,361 cases in 2000 to 291,303 cases in 2005.

It's a "growing epidemic," concludes a research team led by Marya Zilberberg, MD, adjunct professor at the University of Massachusetts, Amherst, and president of the EviMed Research Group.

"Between 2000 and 2005 there was more than a doubling of adult cases," Zilberberg tells WebMD. "And the disease appears to be more likely to be fatal as well, nearly doubling from a 1.2% to a 2.2% case fatality rate."

Last year, a different team of researchers warned that the U.S. C. diff death rate is soaring by 35% a year. The death rate went from 5.7 deaths per million population in 1999 to 23.7 deaths per million in 2004.

Although her team's data don't prove it, Zilberberg thinks the abrupt rise in C. diff death and disease is due to the spread of a new, much more virulent C. diff strain.

Normally, disease-producing C. diff strains make two toxins. The new C. diff NAP-1 strain, according to a 2006 report by CDC researchers Rebecca H. Sunenshine, MD, and L. Clifford McDonald, MD, makes 23 times more of one toxin and 16 times more of the other.

C. diff, shorthand for Clostridium difficile, is a bacterium that lives harmlessly in the gut of many people. Exactly how many isn't known. Other gut bacteria keep it in check -- until a course of antibiotics or an illness upsets the balance. In some cases, C. diff disease can be from a new infection with the bacterium.

When that happens, C. diff can overgrow in the gut in a hurry. Diseases from C. diff can range from mild diarrhea to life-threatening colitis.

The good news is that there are still antibiotics that kill C. diff. The bad news is the bug is now less susceptible to these drugs. And there's more bad news: Relapse is common. As many as one in four patients develop a second episode within two months. And patients who have two or more episodes of C. diff disease run a 50% to 65% risk of another bout.

Elderly patients are most at risk of severe disease. With the U.S. population aging, the growing epidemic worries Zilberberg and colleagues.

"This rapid pace of growth is alarming," they write. "If this rate of rise, along with the increase in virulence and diminished susceptibility to antimicrobial drug treatments, persists, C. diff-associated disease will result not only in a considerable strain on the U.S. healthcare system but also in rising numbers of deaths related to this disease."

Zilberberg and colleagues report their findings in the June issue of Emerging Infectious Diseases.

Show Sources


Zilberberg, M. Emerging Infectious Diseases, June 2008; vol 16.

Sunenshine, R.H. and McDonald, L.C. Cleveland Clinic Journal of Medicine, February 2006; vol 73: pp 187-197.

CDC web site.

Marya Zilberberg, MD, adjunct professor, University of Massachusetts, Amherst; and president, EviMed Research Group, Goshen, Mass.

Redelings, M.D. Emerging Infectious Diseases, September 2007; vol 13.

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