HEALTH

Mutant menaee

A drug-resistant bacterium invades Canada

MARK NICHOLS March 11 1996
HEALTH

Mutant menaee

A drug-resistant bacterium invades Canada

MARK NICHOLS March 11 1996

Mutant menaee

A drug-resistant bacterium invades Canada

HEALTH

The microbe that began showing up

in New York City hospitals in the late 1980s was something doctors had long feared-a potentially

deadly bacterium that was resistant to the most powerful antibiotics. Known as VRE, the bug was a mutant strain of a usually harmless microbe found in the human bowel and

genital tract. VRE (for Vancomycin-resistant enterococci) does not pose a threat to healthy people, but it can be fatal to those weakened by surgery or serious illnesses.

Since it first appeared, the bacterium has spread rapidly in U.S. hospitals and has been linked to the deaths of some patients. VRE was slower to gain a foothold in Canada—but cases have begun to show up around the country over the past two years. Last week, three Toronto-area hospitals had isolated about a dozen patients who were carrying VRE bacteria. Though not actively infected, the carriers posed a threat to other patients. And some doctors

think that VRE poses an even more menacing possibility: that it will transmit its ability to defy antibiotics to other bacteria. “In that case,” says Dr. Donald Low, chief of microbiology at Toronto’s Mount Sinai Hospital, “we would have a true Andromeda Strain.”

VRE made only isolated appearances in Canada until last September, when a major outbreak occurred at The Toronto Hospital; 38 patients were found to be carrying the bacterium and one patient was infected. So far, no deaths in Canada have been attributed to VRE. The prospect raised by Low—of a deadly microbe impervious to any drug—reflects the disturbing talent bacteria have for

evolving new forms. Increasingly in recent years, new antibiotic-resistant strains of bacteria have shown up for such diseases as tuberculosis, meningitis, pneumonia, cholera and syphilis. What frightens doctors about VRE is its resistance to Vancomycin, a drug that usually works when other antibiotics have failed. “It’s a cyclical thing,” says Dr.

Bill Thompson, chief of infectious diseases at The Moncton Hospital, which had two VRE cases last year. “As our medical expertise improves, we are using more antibiotics and keeping more people alive by using techniques that lower their resistance to infection. And the bacteria just keep on evolving.”

The emergence of the drug-resistant bug may be partly the result of North Americans’ profligate use of antibiotics. VRE, notes Low, is not a particularly combative microbe and is normally kept in check by the thousands of other bacterial species that constantly engage in a Darwinian struggle for survival inside human bodies. “But the use of powerful,

broad-band antibiotics on patients,” says Low, “can virtually wipe out everything else, leaving a clear field for VRE.”

Low also contends that VRE is being brought into Canada by travellers from southern European and Asian countries where the bacterium is widespread—or by Canadians who go to the United States for surgery to beat waiting lists at Canadian hospitals. But according to Dr. Verne Glavin, an infectious disease specialist at ChedokeMcMaster Hospital in Hamilton, only one of about 30 VRE cases identified at the hospital since January, 1995, involved a patient who received medical treatment in the United States. What most VRE patients have in common, adds Glavin, is that “they tend to be older people who have been in hospital for a long time and on antibiotics.”

Because there are only a few experimental drugs that have any effect on VRE, hospitals do not try to treat patients who are “colonized” but not infected by it. Instead, says Glavin, the emphasis is on isolating carriers and imposing strict measures to prevent any transmission of the bacterium to other patients.

Many microbiologists say that the greatest danger posed by VRE could materialize in the near future. The bacterium’s ability to resist Vancomycin, says Low, “is located on a gene that can jump into the chromosomes of other bacteria.” The fear is that the gene will jump in-

to a bacterium called MRSA, which is endemic in many U.S. hospitals, and, like VRE, has begun showing up in Canada. Doctors still have a weapon—Vancomycin—that can defeat MRSA. But many experts think it is only a matter of time before a Vancomycin-resistant form of MRSA emerges. “We haven’t seen it yet,” says Tom Skinner, a spokesman for the Centers for Disease Control in Atlanta. The agency, Skinner says, already has an emergency plan in place aimed at isolating and controlling the deadly mutant that could be born at any time.

MARK NICHOLS