It seemed to come out of nowhere — a virulent strain of bacteria called Clostridium difficile. It picked up that name because when it was first discovered, it was difficult to grow in the lab.

C. difficile is not an uncommon bacterium — but it had some infectious-disease specialists worrying that it has become the most dangerous superbug to hit North American hospitals in a decade.

With the death toll reaching at least 460 patients at 22 hospitals in Ontario since 2006, the Ontario government announced it would require hospitals to publicly report the number of cases they were managing. Quebec was the first province to make the move, after 16 people died at the Honoré-Mercier Hospital in St-Hyacinthe after contracting C. difficile between May and November 2006.

C. difficile is now a problem in hospitals throughout the developed world, says Dr. Allison McGeer, director of infection control at Mount Sinai Hospital in Toronto.

What is C. difficile?

C. difficile bacteria grow in the large bowel. They thrive in the stool compressed inside the colon.

The bacteria produce two toxins that cause diarrhea and damage the cells lining the bowel. However, not all strains of C. difficile produce toxin. These strains are unlikely to cause disease and patients colonized by them remain healthy.

In severe cases, C. difficile can cause critical illness and death in elderly or very sick patients.

Why are health care officials concerned?

The experts investigating the 2005 outbreak in Quebec said the bacterium appears to have mutated into a highly contagious and lethal strain — and they don't know why. It has caused almost four times the usual number of cases of severe diarrhea in hospitals, and can persist in the body for months despite repeated antibiotic treatments.

Doctors know C. difficile flourish after patients take certain antibiotics. Now it seems any antibiotic can bring on the disease.

"Something happened 18 to 24 months ago, where the use of particular antibiotics didn't seem to matter anymore," said Dr. Mark Miller, chief of infectious diseases at Montreal's Jewish General Hospital.

Some strains of C. difficile bacteria produce two toxins that cause diarrhea and damage the cells lining the bowel. Courtesy of Lois Wiggs/CDC

In October 2008, researchers in Montreal concluded that hospitals are not the only place that people come down with C. difficile, and antibiotics aren't always linked to the infection, which challenged conventional thinking on the disease.

When people, particularly seniors, pick up C. difficile outside hospitals, it may be because they have a weakened immune system, underlying bowel disease or fewer beneficial flora in the intestines to help keep C. difficile levels in check, said study author Sandra Dial, an intensive-care physician at McGill University Health Centre in Montreal.

In 2011, it is estimated about 250 people in Ontario alone will die of C. difficile, McGeer said.

How do I get it?

The bacteria are often picked up in hospital. Infections tend to arise when a hospitalized patient — who has been unwittingly colonized by the bug — is given antibiotics for another condition.

Your risk of contracting the bacteria rises if you're undergoing chemotherapy, have abdominal surgery or have other stomach or intestine problems.

C. difficile bacteria also make spores that can be found in the environment — on toilet seats or doorknobs, for instance.

How does it spread?

If you get diarrhea from C. difficile infection, you can spread the bacteria by touching something — like a doorknob — if you haven't washed your hands. The spores produced by C. difficile can withstand the effects of drying and direct sunlight and survive on surfaces for weeks.

When someone else comes in contact with those spores and touches their hand to their face, for instance, the spores can get into the gastro-intestinal tract and cause diarrhea.

How is it treated?

Even though the bacteria are sometimes triggered when a patient takes antibiotics, the most effective treatments are certain antibiotics. Short courses — three to five days — of antibiotics such as flagyl and vancomycin are most common. In some cases, doctors also inject patients with immunoglobulins to boost their immune systems.

How is the spread of C. difficile controlled?

Infected patients are often separated from non-affected patients. Hospital staff who deal with infected patients will wear disposable gloves and aprons.

Areas that patients come in contact with are rigorously cleaned with warm water and detergent to remove spores that can spread the condition.

The most efficient way to prevent person-to-person spread of C. difficile is to thoroughly wash your hands before and after patient contact.

Controlling C. difficile in hospitals is a complicated and expensive issue that involves not only limiting use of antibiotics but also cleaning electronic equipment used to take care of patients and building facilities with private rooms, McGeer said.

What should I do if I'm caring for someone affected by C. difficile?

Wash your hands often:

• Before you eat or prepare food.
• After you use the toilet or handle a bedpan.
• Before and after you touch a person with C. difficile.

More tips:

• If you must handle stool, wear rubber gloves.
• Clean the washroom daily.
• Put disposable wastes — like diapers — into plastic bags, tie them and discard with the rest of the trash.
• If clothes are heavily soiled with stool, wash them separately with detergent and bleach. Do not mix with the rest of your laundry.