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Risk Factors for C. diff Include Antibiotic Use and Being Over Age 65
By Charlene Laino
WebMD Health News
Reviewed by Louise Chang, MD
Each year, C. diff strikes about 500,000 Americans, mostly in hospitals and nursing homes. But anywhere from 15,000 to 180,000 of those cases are now acquired in the community, says Erik Dubberke, MD, an infectious diseases specialist at Washington University in St. Louis.
Why the huge range? Estimates are based on one-year snapshots of different communities, with no studies tracking cases over time, Dubberke tells WebMD.
"We know community-acquired C. diff is on the rise," though no one knows to what degree, he says.
Dubberke was one of several researchers who discussed C. diff at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy.
C. diff Risk Factors
Most cases of hospital-acquired C. diff occur in people taking so-called broad-spectrum antibiotics, including clindamycin, fluoroquinolones, and penicillins that kill many different types of pathogens.
Spores enter the body through the mouth, which is the entryway for the gastrointestinal tract. The broad-spectrum antibiotics kill "good" bacteria in the gut that keep C. diff. at bay.
Use of antibiotics is also a risk factor for community-acquired C. diff, but not to the same degree. Studies implicate antibiotics in as many as 90% of hospital cases, but fewer than half of community-acquired cases, Dubberke says.
Other risk factors include age over 65 and recent discharge from the hospital. "You're at risk for the first few weeks after you get out. Then, there's a rapid decline for 12 weeks until you're back to [average] risk," he says.
In younger people, underlying medical conditions such as lung disease may increase susceptibility to the bug.
People who have already had a few bouts with C. diff are especially at risk, says the CDC's C. diff expert, Clifford McDonald, MD.
"If you've had three or four recurrences, your likelihood of another recurrence is over 50%," he tells WebMD.
Glenn Songer, PhD, of Iowa State University College of Veterinary Medicine in Ames, is concerned that food may be the source of many unexplained infections.
"We found contamination in 40% of beef, pork, and turkey products we tested. And the C. diff isolates [strains] were the same isolates that cause disease in humans. We have just not yet proven a flow [of C. diff disease] from animals to humans," he says.
Still, the vast majority of cases are spread from human to human. Asked what he does to ensure the food he brings to his table is safe, Singer concedes, "I just go ahead and eat what I want."
That said, he and others are continuing to study farm animals and the food supply and culture samples of retail meats for C. diff.
Patient-to-Doctor Spread of C. diff
Researchers at the meeting reported that patients who have recently recovered from community-acquired C. diff may spread it to doctors and nurses who see them for follow-up visits.
Forty-five percent of gloves worn by health care workers who touched the skin of 35 such patients tested positive for C. diff spores, says Lucy Jury, RN, MSN, a nurse researcher at Louis Stokes Department of Veterans Affairs Medical Center in Cleveland.
In a separate study, Jury and colleagues found that two simple questions -- asking whether a patient has had a C. diff infection and/or has been on broad-spectrum antibiotics within the past three months -- can identify the majority of so-called carriers of C. diff. Carriers don't have symptoms but are shedding spores and can spread the disease.
In the study of 120 nursing patients followed for five months, the two questions correctly identified about three-fourths of carriers.
While nearly one-fourth of cases were missed, "it's the best we have," Jury tells WebMD.
C. diff Recurrence
A mid-stage, industry-funded study showed that a novel antibiotic known as CB-183,315 appears safe and more effective than the drug vancomycin (Vancocin) at preventing recurrences of C. diff infections.
Vancomycin and metronidazole (Flagyl) wipe out C. diff in 80% to 90% of patients, says researcher Thomas Louie, MD, an infectious diseases specialist at the University of Calgary, in Canada. But after seemingly successful initial treatment, symptoms come back in 25% or more of patients, he tells WebMD.
In the new study, vancomycin was associated with a 35% recurrence. Low- and high-dose CB-183,315 had recurrence rates of 28% and 17%, respectively.
"That's the big bear we're all trying to tackle -- the recurrence rate," says James McKinnell, MD, of Harbor-University of California, Los Angeles Medical Center. He was not involved with the work.
Larger, longer phase III studies are needed to confirm long-term safety and effectiveness.
Preventing C. diff
So what should you do to avoid C. diff? Two simple steps will go a long way toward keeping you infection-free, experts say:
- Don't demand antibiotics if your doctor says you don't need them.
- Wash your hands thoroughly and frequently.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.