NEWS

NDM-1 Superbug Acquired In Canada

05/30/2011 02:44 EDT | Updated 07/30/2011 05:12 EDT

(The Canadian Press) -- TORONTO - Canadian researchers have identified what appears to be the first domestically acquired case of an NDM-1 superbug.

An 86-year-old Ontario man was found to be carrying bacteria resistant to most antibiotics because of NDM-1, or New Delhi metallo-1, an enzyme that alters the DNA of various types of bacteria. NDM-1 is endemic in India and Pakistan and has spread worldwide due to global travel.

But the patient, who was admitted to hospital and then a rehabilitation centre after suffering a stroke last October, had not travelled outside southwestern Ontario for the last decade. None of the man's family members or other close contacts were carrying the superbug, nor had any been to parts of the world where NDM-1 is widespread.

"So it's really unfortunately a mystery in terms of his source, and it certainly suggests that he acquired it here in the southwestern Ontario region," said Dr. Susan Poutanen, an infectious disease physician at Mount Sinai Hospital in Toronto.

"So whether it was in Toronto, whether it was outside of Toronto, whether it was in hospital or whether it was in the community, at this point we really can't say," added Poutanen, principal investigator of a study describing the case.

She said the case is not cause for public alarm but is meant to alert hospitals and laboratories not to dismiss NDM-1 as a cause of drug-resistant bacteria in patients merely because they have not travelled outside Canada.

So far, 28 cases of NDM-1-related cases have been reported across the country, a spokeswoman for the Public Health Agency of Canada said Monday. All but the 86-year-old's case have been traced to travel in India or Pakistan.

At least two of those patients died, although not directly from the superbugs they harboured. NDM-1 has primarily been found in E. coli and Klebsiella bacteria, which are common causes of urinary-tract infections and pneumonia.

The Ontario man, who was colonized with an NDM-1 superbug but exhibited no symptoms of infection, was not treated with the one antibiotic to which the bacteria was susceptible to avoid the organism from developing even further drug resistance.

The bacteria — Morganella morganii, a cause of urinary tract and other infections — did not make the patient sick, but his intestinal system has remained colonized with the altered microbe and close family members are being regularly screened in case of possible transmission.

For privacy reasons, the hospital and rehab centre where the man was treated for his stroke are not being disclosed, but testing showed he had not spread the superbug to others, said Poutanen. "They screened every patient on the wards where he had been; no one was carrying the NDM-1-containing organism."

In a report on the case published Monday in the Canadian Medical Association Journal, Poutanen and colleagues also describe another patient found to be colonized with a different type of bacteria, also rendered multidrug-resistant by NDM-1.

Last September, the 71-year-old woman was seen at a Toronto hospital after returning from India, where she had travelled to obtain an MS-related medical procedure not available in Canada. Doctors chose not to treat the women with either of the only two antibiotics to which the bacteria remained susceptible, again because the organism was not causing any symptoms.

Poutanen said that while there is no threat to the community at large, infectious disease experts want to keep on top of NDM-1 to make sure it doesn't take hold as it has in some countries.

"The reason why we're at all even looking at it is simply if somebody does become infected, it really is a challenge because there are so few treatment options," she said. "So we want to try to avoid people getting infected, which means we'd like to avoid persons becoming colonized and the spread of this bug."

Dr. David Patrick, director of the school of population and public health at the University of British Columbia, agreed there is no need for public alarm.

"Secondary transmission after importation is possible, but it's important for all of us to remember that sporadic transmission doesn't necessarily mean a pattern that's going to spread throughout the population," said Patrick, who was not involved in the research.

"The main thing we need to understand is if the overall pattern of resistance in our environment and in human beings is changing significantly in Canada — and I don't see that this study has shown that."

Still, Patrick suggests it would be prudent to keep tabs on close contacts of travellers who return to Canada carrying an NDM-1 superbug to see if transmission does occur and how often.

"And if we're not seeing it in the families and close contacts, from the people who they share food and toilets with, then it's not going to be a risk to the general community."

Poutanen said the thrust of the CMAJ report is primarily to alert infectious disease specialists across the country about the occurrence of the home-grown case.

"We do want to make sure that laboratories and hospitals are ready, one, for identifying it in the lab and, two, acting upon it from an infection-control point of view to make sure we stay above this and that we don't let it become endemic in our regions — and that we keep it at bay as much and as long as possible."

The study authors want to encourage hospitals to follow Public Health Agency of Canada guidelines on infection control and to lab-verify any test results showing antibiotic-resistant organisms from patients, even when they have not travelled to NDM-1-endemic countries.

Poutanen said she and her colleagues would like public-health authorities to make all NDM-1 cases reportable, so that any spikes in incidence can be spotted and steps taken to contain possible transmission. Other superbugs — such as methicillin-resistant staphylococcus aureus, or MRSA — are reportable diseases.

"The whole idea of keeping ahead of the game is to avoid that worst-case scenario where we're seeing this more endemic and transmission in hospitals as we're seeing with MRSA and the like. We don't want to see that."