Dangerous superbug in Canada

Canadian Press
Jun. 28, 2006

TORONTO (CP) - A dangerous strain of a superbug that can be caught outside hospital settings has moved beyond the boundaries of the high-risk groups it first plagued in Canada, causing illness in healthy adults and children in a number of provinces across the country, researchers reported Tuesday.

In a series of articles and commentaries rushed to print by the Canadian Medical Association Journal, they reported on the spread of community-acquired methicillin-resistant Staphylococcus aureus - known in the medical community as CA-MRSA.

The drug-resistant forms of the bug that are spreading in the community - strains labelled USA300 and USA400 - generally cause hard-to-treat skin and soft-tissue infections, weeping wounds that will not heal. But they can also occasionally cause severe illness and even death in previously healthy individuals.

"It's sweeping across the nation, no doubt about it," said Dr. John Conly, senior author of one of the papers and a leading researcher on the scope of Canada's problem with community-acquired MRSA.

"I think this is a pan-Canadian problem."

Historically, infections caused by antibiotic-resistant strains of Staph aureus were transmitted in hospitals, where the heavy use of antibiotics has allowed a variety of drug-resistant bacteria to flourish.

But over the past 10 or 15 years, public health authorities in first Australia and later the United States and Europe reported the troubling emergence of a couple of virulent strains of MRSA that seem to have developed in the community, in people who hadn't been hospitalized.

Some groups in the community have been known to be at high risk - the homeless or residents of homeless shelters, intravenous drug users, crack cocaine smokers, prison inmates and men who have sex with men. Frequent skin-to-skin contact, crowding and suboptimal hygiene are believed to facilitate the bugs' spread.

But in the United States, where the problem is more advanced than it has been to date in Canada, infections have been cropping up in day-care centres and on sports teams, both professional and amateur.

Conly said U.S. public health authorities estimate the case load runs to the hundreds of thousands.

"Washington, Oregon, California and Texas - they've got 15-, 16-year-olds on ventilators and are seeing really quite devastating pneumonias as a result," he said from Calgary, where he teaches medicine at the University of Calgary.

"So this is really quite a serious issue and I think it's an important one from a standpoint of Canadian physicians to realize that this is not actually something south of the border but has swept up from the southwestern United States and is now sweeping across Canada."

Conly, who chairs the Canadian Committee on Antibiotic Resistance, said Calgary has already seen 300-plus cases of community-acquired MRSA, including four or five deaths.

And while Calgary's outbreak seemed to predate others in the country, communities in southwestern British Columbia, Saskatchewan, Manitoba and beyond are seeing an upswing in cases, he said.

Dr. Allison McGeer, head of infection control at Toronto's Mount Sinai Hospital, said the problem is being seen in Canada's largest city as well.

"Where we used to see none a decade ago and one or two a year starting five years ago, last year there were probably 12 or 15 (cases)," McGeer said of her hospital alone.

"It's beginning to be a regular feature."

Some of the cases are in people from known high-risk groups; but others are in patients who have no obvious risk of developing CA-MRSA, she noted.

In jurisdictions where CA-MRSA has been a problem for a while, the virulent community strains have started colonizing hospitals, leading to higher rates of hospital infections and deaths associated with this superbug.

McGeer expects this to happen in Canada too, saying the drug-resistant forms of Staph aureus will drive out the easier-to-treat strains that are susceptible to more antibiotics.

"Eventually it's clear that these strains are going to take over," she said.

A commentary on the issue insisted, though, that it's too soon to throw in the towel, calling for a concerted effort to combat the spread of the superbug.

"Given that MRSA does not respect provincial, territorial or other jurisdictional boundaries, national collaborative efforts are required," wrote Dr. Upton Allen, an infectious disease expert at Toronto's Hospital for Sick Children.

Both Conly and McGeer said it is important for Canadian physicians to consider CA-MRSA when seeing patients with skin and soft-tissue infections and to test the wounds for the presence of drug-resistant microbes, so doctors don't end up treating patients with drugs that will have no impact.