Infection with potentially deadly Clostridium difficile is often linked to antibiotic use, but new research suggests antibacterial drugs may be getting too much of the bad rap and that other factors may also be to blame.

In a study of C. difficile infections among people living in the community -- as opposed to those sickened by the bug while in hospital -- McGill University researchers found that a significant proportion of those who got C. diff-related disease had not recently taken antibiotics.

The study of 836 people aged 65 or older with C. difficile found 53 per cent had not taken antibiotics in the 45 days preceding hospitalization for their infection.

While C. difficile is mainly known as a hospital-acquired infection, the study participants had not been in hospital for at least 90 days before being admitted after being sickened by the infection.

"Essentially, what we were trying to address is the idea that only patients who have taken antibiotics get C. diff," said principal author Dr. Sandra Dial, a critical-care specialist at McGill. "And so what we wanted to examine was could we confirm that people get Clostridium difficile without antibiotic exposure."

"So what we're saying is if patients, particularly elderly patients, who have any sort of bowel disorder present with severe diarrhea, still test them for C. diff even if you don't get a history that they've been in a hospital or that they've taken antibiotics in the recent past."

Dial said C. difficile occurs most often among patients already in hospital, because transmission is easier. In the community, cases are proportionately fewer and the circumstances needed for transmission are less prevalent, she said, so other factors must come into play. Those include people with underlying bowel disease, weakened immune systems and disruptions to intestinal flora that normally would keep C. difficile from reproducing in large enough numbers to cause disease.

"And the other thing that keeps coming up again and again is older age," Dial said. "So something must be happening to your immune defences against this bacteria as you get older."

She said the main reason researchers looked at community-acquired C. difficile is because they thought "it could make the picture a little clearer than looking at it in a hospital where so many things are closely tied."

Dial also believes use of antacids known as proton pump inhibitors may strip away one of the body's defences against the bug by limiting stomach acid.