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C. diff Epidemic: What You Must Know

Why C. diff Is Spreading, Why It's More Deadly, How to Protect Your Family

Is C. diff a superbug?

"Superbug" is not a scientific term. The CDC's McDonald prefers to avoid it. The media originally coined the term to refer to germs that, like Superman, became bulletproof: That is, they became impervious to drugs that kill other germs. Dictionaries reserve the "superbug" designation for germs resistant to drugs that used to kill them.

"Superbug" has also been used to describe germs that, like many superheroes, once were normal but become super strong: That is, they became much more virulent than they used to be.

"I think if I were to use the word "superbug" I might use it to connote a particular strain or strains of a pathogen in which there has been a convergence of increased resistance to antibiotics ... and increased virulence," McDonald says.

All C. diff strains are resistant to many of the antibiotics normally used to treat other infections. In fact, that's the problem. C. diff most often strikes people whose intestinal flora have been disrupted by antibiotic treatment. But most C. diff strains remain sensitive to Flagyl and vancomycin, the drugs normally used to treat this infection.

The NAP1 strain of C. diff, however, is even more resistant to fluoroquinolone antibiotics than other C. diff strains. It makes 20 times more toxin than normal strains. And most importantly, there's evidence it causes more severe disease than other strains.

For these reasons, C. diff NAP1 is now being called a superbug, although you won't see the term in scientific reports.

Why are C. diff cases rising so rapidly?

The number of hospital patients with C. diff infection went up and down a bit from 1996 until 2000. But from 2000 to 2001 there was a steep increase -- and that increase continued at least through 2006. Preliminary data suggest the epidemic may have slowed a bit in 2007, but McDonald says it's too soon to say it's leveled off.

What happened in 2000? McDonald says that's when the NAP1 strain -- which has been around for at least 30 years -- developed fluoroquinolone resistance. This resistance, plus what McDonald calls the strain's "hypertoxin production," may explain why this strain has taken off.

Another reason for the epidemic is the rise of community-acquired C. diff infection. C. diff usually is thought of as a hospital infection, and community cases were thought to come from people who got C. diff during a hospital stay but who didn't develop symptoms until they got home.

A 2006 study in Connecticut showed that community-acquired C. diff disease struck seven people out of 100,000. One in four cases did not have the risk factors normally associated with C. diff. Moreover, a third of these cases had no exposure to antimicrobial drugs.

Where is the C. diff coming from? The vast majority of cases come from person-to-person transmission (see below).

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