New Threat From An Old Bug

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The ongoing epidemic of severe C. diff diarrheal disease — driven by a 20-fold more toxic mutant strain of the bacteria — is fast getting worse.

C. diff is shorthand for Clostridium difficile. About 3 percent of the population carries the bug without knowing it. Normal gut bacteria usually keep C. diff in check. Many antibiotics that kill normal bacteria don't kill C. diff. That lets it take over the gut during or after antibiotic treatment.

Spread by spores that can live for months on dry surfaces, the bug makes a toxin that poisons the intestine. Disease ranges from mild diarrhea to life-threatening colon infection with profuse diarrhea.

Once mostly confined to elderly, hospitalized patients, a bad new strain of the bug is attacking healthy, young people outside the hospital. The full extent of this community spread of C. diff isn't yet known. But it's a growing problem, says CDC medical epidemiologist L. Clifford McDonald, M.D.

"We have seen this bacteria in people not usually infected with it," McDonald tells WebMD. "We see generally healthy, young people who had not been in the hospital coming down with severe C. diff disease."

McDonald's CDC team made one of several reports on the alarming C. diff epidemic at this week's annual meeting of the Infectious Diseases Society of America (IDSA), held Oct. 12-15 in Toronto, Ontario.

Nasty New Bug

It's not yet clear what is behind the new epidemic of C. diff disease. There are several factors:


  • The bug is becoming resistant to the most commonly used antibiotics.
  • A kind of heartburn drug called a proton-pump inhibitor — including Aciphex, Prevacid, Nexium, Prilosec, and Protonix — appears linked to C. diff infections.
  • A bad new strain of C. diff is spreading across the globe.

It's that bad new bug that most worries Fred Arthur Zar, M.D., medical director at the University of Illinois Hospital and professor of medicine at the University of Illinois at Chicago.

"The new strain of C. diff has become the most predominant strain," Zar tells WebMD. "The reason it is more nasty is it mutated and figured out a way to make 20-fold more toxin than the normal strain. ... If you have it, you get sick, and you need medical attention."

In addition to making about 20 times more of the two toxins produced by normal C. diff, the new strain makes a new, third toxin similar to a toxin seen in other disease-causing bacteria.

According to the CDC, the new strain of C. diff already has invaded at least 19 U.S. states: California, Connecticut, Florida, Georgia, Illinois, Maine, Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, Tennessee, Texas, Washington, and Wisconsin.

It has spread throughout Canada and, according to McDonald, is "wreaking havoc" in England, the Netherlands, Belgium, and France.

Vancomycin to the Rescue?

As it happens, Zar had been studying the best way to treat C. diff infection when the current epidemic broke out. In a clinical trial, he's been comparing the currently recommended treatment for C. diff — the antimicrobial drug Flagyl — with a powerful antibiotic called vancomycin.

Vancomycin is known to work against C. diff. But doctors have been reluctant to use it — not only because it costs more, but also because it's the last line of defense against a number of other nasty infections. Once it's in common use, it's only a matter of time before many of these germs become vancomycin resistant.

However, Zar's team reported to the IDSA that vancomycin cures severe C. diff disease 97 percent of the time — compared with a 76 percent cure rate for Flagyl.

"Fortunately, we've seen no vancomycin resistance in C. diff — yet," Zar says. "But e know that the bug can develop resistance to this antibiotic."

Community Infections Spreading

McDonald isn't yet ready to blame all of C. diff's resurgence on the bad new strain. Nor is the CDC yet sounding the alarm over the community spread of C. diff. But his CDC team has documented a growing problem.

Together with Duke University researchers, McDonald's CDC team analyzed more than 1,200 C. diff cases treated at six North Carolina hospitals.

"The general picture is that about one in five cases of C. diff in North Carolina hospitals were community-associated — we think community-acquired — in people not hospitalized for at least three months, most of them not for two years," he says.

That comes out to as many as 30 cases per 100,000 population per year — as much as a threefold jump over previous rates. Even though doctors don't routinely report C. diff infections, the CDC has documented a sharp rise in cases. The latest statistics show that this increase continues to accelerate.

"This tells us that community-acquired C. diff is a lot more common than we would have thought," McDonald says. "In the past, we felt it was a prerequisite for people to have antibiotic exposure to get C. diff. And these community cases we looked at, over half had no antibiotic exposure. That is making a lot of us scratch our heads."

It may be that C. diff disease will become as big a problem as the current epidemic of drug-resistant staph infection.

"This epidemic is very concerning because it is so dynamic," McDonald says. "We are seeing a very steep curve upward in C. diff cases. Anything moving that quickly we need to address seriously — and we are."

What to Do

McDonald and Zar stress two points. The first is that taking antibiotics is not without risk — and one of the risks is C. diff disease.

The other point is that C. diff infection can be prevented — by hand washing. Unfortunately, alcohol-gel hand sanitizers don't kill C. diff. McDonald and Zar warn anyone who has contact with a diarrhea patient to thoroughly wash their hands with soap and warm water.

Finally, McDonald and Zar warn people to be on the lookout for C. diff symptoms.

"If you get diarrhea that lasts more than three days, or if you get diarrhea accompanied by fever or blood in the stool, seek medical attention," McDonald says.


SOURCES: 2006 Annual Meeting of the Infectious Diseases Society of America, Toronto, Ontario, Oct. 12-15, 2006. Clifford McDonald, M.D., medical epidemiologist, CDC, Atlanta. Fred Arthur Zar, M.D., medical director, University of Illinois Hospital; professor of medicine, University of Illinois at Chicago. CDC web site.


By Daniel DeNoon
Reviewed by Louise Chang