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Researchers from the U.S. Centers for Disease Control and Prevention (CDC) found that about 82 percent of Clostridium difficile, or C. diff, cases in healthy people occurred after visiting healthcare settings - like doctors' offices and emergency rooms.

"I think people should be aware of the source," said Dr. Fernanda Lessa, a medical epidemiologist in the surveillance branch of the division of healthcare quality promotion of the CDC and the study's senior author.

People typically pick up C. diff bacteria, which can cause severe diarrhea, during a hospital stay - especially after antibiotics kill off beneficial gut bacteria, allowing harmful bacteria to thrive.

But C. diff has been increasingly reported in young and healthy people who didn't stay in the hospital, Lessa and her colleagues write in JAMA Internal Medicine, adding that between 20 and 28 percent of C. diff cases are in healthy people.

To get a better understanding of possible sources of C. diff infections among otherwise healthy people, Lessa and her colleagues analyzed telephone interviews with 984 infected people in eight states from 2009 through mid-2011.

Overall, the team found that 18 percent didn't report any recent visits to a healthcare facility. The rest did report visiting doctors' or dentists' offices or even having been in a hospital for less than a day, such as for outpatient surgery.

Those locations can be the source of C. diff infections in two ways - direct contact with contaminated surfaces or, indirectly, from healthcare providers prescribing antibiotics that kill off friendly bacteria and leave a person more vulnerable to C. diff.

About 64 percent of the infected people reported taking antibiotics during the previous 12 weeks. Those who took antibiotics were also more likely to have some sort of exposure to a healthcare facility.

Other possible sources of exposure to the C. diff bacteria are infected family members - especially babies, who can carry the bacteria without showing any symptoms.

The study participants who weren't exposed to a healthcare facility were also less likely to have taken antibiotics, but more of them were exposed to a third possible risk factor: heartburn drugs known as proton-pump inhibitors, which are used to control stomach acid.

Previous research has tied proton-pump inhibitors - such as Prilosec and Nexium - to C. diff in healthy people. That evidence led the U.S. Food and Drug Administration to issue a warning about the association in February 2012, according to Dr. Kent Sepkowitz, in a commentary accompanying the new study.

"People should just be cautious about taking them willy-nilly. There are certainly people who need to take them, but then there are many who don't," said Sepkowitz, director of infection control at Memorial Sloan-Kettering Cancer Center in New York.

Dr. Peter Green from the Celiac Disease Center as Columbia University in New York said the drugs may create a hospitable environment for the C. diff bacteria to survive or - like antibiotics - they may disrupt the colon's "good" bacteria.

"It's very interesting because these proton-pump inhibitors are very widely used. People tend to get them and they just stay on them. Part of that is that they actually work to reduce heartburn symptoms," he said.

Green, who was not involved with the new study, said doctors are trying to get some people off the drugs because of their associations with C. diff, osteoporosis and other gastrointestinal infections.

"They're being used much more than is really necessary," he said.

Lessa cautioned, however, that it's not possible to draw firm conclusions from their study about what's causing the infections because it didn't compare the C. diff patients with a control group.

"The next step now is that we're undertaking a case-control study, enrolling patients without C. diff infections and test the hypotheses that were raised by this study," she said.

SOURCE: bit.ly/10y9upJ JAMA Internal Medicine, online June 17, 2013.