Rates of Clostridium difficile, an often recurring bacterial infection of the colon that causes debilitating diarrhea, have fallen dramatically in hospitals across Canada since 2009, a study has found.

In a study published Monday in the Canadian Medical Association Journal, researchers report that hospital-associated C. difficile infections dropped by 36 per cent between 2009 and 2015.

"There's probably a number of interventions that led to that decrease," said lead author Dr. Kevin Katz, medical director of infection prevention and control at North York General Hospital in Toronto.

Improvements in infection control measures, such as improved testing, more judicious use of antibiotics, frequent hand-washing and more frequent, intense cleaning of hospital facilities in the last decade may have contributed to the drop in infection rates, he said.

While a virulent form of C. difficile known as NAP1 was found to be the most common strain affecting patients during the seven-year study, the proportion of cases it caused compared to other strains had also diminished, researchers said.

C. difficile is the most common infectious cause of diarrhea in hospitalized patients in developed countries, leading to severe illness and in some cases death. Seniors and people taking antibiotics are most vulnerable to the infection.

Broad-spectrum antibiotics taken for another infection can kill so-called good bacteria in the gastrointestinal tract, allowing C. difficile to flourish in those exposed to the bug.

C. difficile bacteria produce a toxin, which causes inflammation of the colon. The microbe also creates difficult-to-eradicate spores, which can contaminate surfaces in hospital rooms and rapidly spread the infection.

Doctors treat C. diff with more targeted antibiotics, but the bacteria have developed resistance to some of them, often making the illness more challenging to overcome.

NAP1, which is resistant to fluoroquinolone antibiotics, has been responsible for a number of hospital-associated outbreaks over the years, including a Quebec epidemic that began in 2002. Over the next few years, thousands of patients developed the disease and at least 2,000 died.

"What's special about NAP1 ... is [its] ability to produce a lot more toxin," said Katz, noting that spores produced by the strain are much harder to destroy through cleaning than "regular germinating bacteria."

Infection leaves patients in debilitated state

To conduct the study, researchers from the Canadian Nosocomial Infection Surveillance Program looked at data from acute-care hospitals across the country between 2009 an 2015. Nosocomial means acquired during hospitalization.

A total of 20,623 cases of hospital-associated C. difficile occurred during the network's study period, mostly in hospitals with more than 200 beds. Over that seven-year timeframe, 158 deaths were attributed to the infection, mostly among older people.

Dr. Christine Lee, an infectious disease physician and medical microbiologist at St. Joseph's Hospital in Hamilton, was not surprised to see the national drop in the number of C. diff infections, an occurrence mirrored at her hospital and others in the region.

Concerted effort to prevent infections

"I think it's because of a concerted effort between the infection prevention at each hospital and more hypervigilance by the health-care providers," said Lee, who was not involved in the study.

"When people work together in a concerted effort, it does make a positive difference."

Lee said C. difficile not only causes symptoms like severe diarrhea, but the infection often recurs in patients, despite treatment.

"It leaves them in a much more debilitated state, it makes them more anxious and socially isolated," she said, noting that those affected worry about the infection coming back and the potential of transmitting it to others.

"I've had some women who were asked not to come to visit to see their grandchildren," said Lee. "That is heart-breaking to hear."

Katz said seeing a 36 per cent decline in infection rates across the country reflects a major advance in patient safety.

"To have such a remarkable drop over such a small number of years is great news," Katz said.