Health authorities in Minnesota have been trying to reduce the spread of antibiotic-related germs by discouraging doctors from overprescribing the drugs — but new data suggests they need to be concerned about dentists as well.

Epidemiologists with the Minnesota Department of Health reviewed 1,626 cases of a nasty intestinal infection known as Clostridium difficile, or C. diff, that occurred from 2009 to 2015 outside of hospitals or health care facilities.

Among them, 926 involved people who had recently taken antibiotics. That’s not surprising, because the C. diff bacteria often swoop in after antibiotics have suppressed other germs in the body.

But experts were surprised to find that 136 people received the antibiotics for dental procedures. The results were presented last month at a science symposium in San Diego.

Dentists used to prescribe antibiotics prophylactically — to prevent bacterial infections from emerging — before some oral procedures, but the practice isn’t recommended as much today, said Dr. Amanda Beaudoin, who directs a state program, One Health, designed to get health care professionals and the public on board with conserving antibiotics.

“Dentists have been overlooked and actually do a lot of prescribing to patients who end up getting C. diff,” she said.

Results are mixed in the state’s overall fight against infections that are tied to antibiotic overuse.

Methicillin-resistant Staphylococcus aureus, or MRSA, emerged over the last half-century as bacteria evolved in response to the broad use of antibiotics. But the rate of MRSA has been cut almost in half since 2004 in Hennepin and Ramsey counties, state health data shows. Beaudoin said that is largely due to hospitals following strict guidelines for preventing infections from spreading to patients.

However, Minnesota’s rate of C. diff is rising — especially the rate of infections that occur outside hospitals. C. diff is a common cause of diarrhea and fatigue but can also lead to potentially fatal complications in the colon.

While not all cases are linked to antibiotics — people who are older or in hospital care also are at higher risk of infection — the overuse of these drugs remains a leading culprit, Beaudoin said. “We still estimate that up to 30 percent of antibiotics that are used in the outpatient settings are inappropriate or unnecessary.”

The public can help, especially in the cold and flu season, by not pressuring doctors for antibiotics, which don’t work against the viruses that cause common illnesses, she noted.

People should not save unused antibiotics, she added, nor should they flush them down sinks or throw them in the trash because of the risk that they will eventually seep into the environment and drinking water supplies.

The Minnesota Pollution Control Agency website lists more than 240 safe disposal sites in the state.