CDC questions C. difficile's tie to antibiotic use

Judicious antibiotic use and careful hygiene practices, including washing with soap and water, are important in curbing new outbreaks.

By Susan J. Landers — Posted Dec. 26, 2005

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Washington -- Diarrhea associated with toxins produced by Clostridium difficile is strictly related to antibiotic use, right? Well, maybe not.

C. difficile seems to be changing. Cases have been noted among people with no recent history of antibiotic use, a previously consistent hallmark for runaway toxin production by the spore-forming bacteria. The concern is that the disease may be in mid-leap from being a hospital-based, antibiotic-associated illness that is particularly harmful to elderly people to being a condition circulating in the community and affecting younger people.

The Centers for Disease Control and Prevention is urging physicians, including office-based physicians, to consider ordering tests for the bacteria sooner rather than later for patients with severe diarrhea.

"Think outside the box a little bit," suggested L. Clifford McDonald, MD, a medical epidemiologist at the CDC, and the author of a report on the problem in the Dec. 2 Morbidity and Mortality Weekly Report. "C. diff could be changing. We don't fully understand why right now."

What is known is that a new strain of the bacteria is causing hospital outbreaks in several states and in Canada. The new strain appears to be more virulent and linked to the use of fluoroquinolones, according to a study in the Dec. 8 issue of The New England Journal of Medicine, of which Dr. McDonald is the lead author.

A second study in the same issue examined outbreaks of C. difficile-associated diarrhea in 12 Quebec hospitals and identified a common predominant strain among the hospitals, said lead author Vivian Loo, MD, chief of microbiology at McGill University Health Center in Montreal.

Her study identified a mutation in a gene that resulted in the production of more toxins by the bacteria and the likelihood that the disease it could cause would be more severe. "The study also highlights that this is a regional problem and not just a problem at one hospital," she said.

The significance of this finding is unclear. "Right now we can't say that it's the [new strain] that could explain a jump to the community," Dr. McDonald said.

The CDC investigated several serious cases this year among young, healthy patients with no exposure to health care settings, he said. "Eight of the 33 cases of C. difficile-acquired disease studied had no antibiotic exposure either, which is really unusual."

But the investigation disclosed that whether a family member of an ill patient had recently taken an antibiotic does seem to play a role, and there is reason to think that pregnancy might predispose a person, he said.

The fact that a patient with diarrhea had no exposure to antibiotics ordinarily would make a physician less suspicious that these bacteria were the cause, Dr. McDonald noted. "Diarrhea is such a common illness that it is not usually worked up. Most of the time it's viral. And that's still true."

"But if [the diarrhea] lasts longer than three days, you should start thinking about getting some tests. Also, if it's accompanied by a high fever or there's blood in the stool or abdominal pain or they look or feel sick, you might order tests earlier."

Keeping your guard up

Whether C. difficile is following the same path blazed by several other pathogens in recent years was the subject of an editorial in the same issue of NEJM by John G. Bartlett, MD, chief of the division of infectious diseases at Johns Hopkins University School of Medicine and Trish M. Perl, MD, senior hospital epidemiologist at Johns Hopkins.

The researchers point to avian influenza, severe acute respiratory syndrome and community-acquired methicillin-resistant Staphylococcus aureus as examples of old pathogens arising to cause new concerns.

All pose challenges to scientists who attempt to explain their re-emergence, to clinicians in treating patients and to infectious diseases specialists in preventing their spread. C. difficile may be the most recent example.

"In the past 20 years," the researchers write, "C. difficile has become the most commonly recognized microbial cause of nosocomial diarrhea, reflecting high rates of colonization in hospitalized patients and the frequent use of antimicrobial agents."

CDC officials speculate that the change in the disease may be caused by new patterns in antibiotic use, ineffective infection-control practices or the newly emerging strain.

Warnings about the overuse of antibiotics and the rise of resistant strains of bacteria have been voiced for several years by infectious diseases specialists. "This is one additional unintended consequence of inappropriate antibiotic use," said Dale Gerding, MD, associate chief of staff for research and development at Hines Veterans Administration Hospital and professor of medicine at Loyola University's Stritch School of Medicine in Chicago. "Prescribers and patients need to think carefully about whether their illness requires treatment with an antibiotic."

There are major downsides to the overuse of antibiotics, including development of resistance to the drug by mutating bacteria, and overuse is frequently the reason for C. difficile diarrhea.

However, such disease should still be treated with a course of antibiotics, and metronidazole or vancomycin are the best choices, the CDC said.

Particular attention to hand hygiene also is encouraged.

A study by Dr. Gerding, recently presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy meeting, found that the use of alcohol-based hand washes did not kill all C. difficile spores on the hands of volunteers. Soap and water did a better job.

"In our hospital, when we have a patient with C. difficile, we use hand washing rather than alcohol," said Dr. Gerding, "and we use gloves as well."

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Prevention strategies

  • Use antibiotics judiciously.
  • Use contact precautions for patients with known or suspected C. difficile-associated disease.
  • For outbreaks, consider using only soap and water for hand hygiene when caring for patients with C. difficile-associated disease; alcohol-based hand rubs might not be as effective against spore-forming bacteria.
  • Implement an environmental cleaning and disinfection strategy.
  • Use an Environmental Protection Agency-registered hypochlorite-based disinfectant for environmental surface disinfection after cleaning in accordance with label instructions.

Source: The Centers for Disease Control and Prevention

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External links

The Centers for Disease Control and Prevention on a new strain of Clostridium difficile (link)

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