TORONTO - There has been a sharp increase in the percentage of gonorrhea cases in Ontario that are resistant to antibiotics that until recently were potent and simple-to-use weapons against the sexually transmitted infection, a new study published Tuesday reveals.

The research showed that 28 per cent of gonorrhea samples tested in 2006 were resistant to fluoroquinolone drugs, up from four per cent in 2002. And in selected sites, it was even higher, according to the study, which was published in the Canadian Medical Association Journal.

Fully 55 per cent of samples from one unnamed clinic -- identified by the researchers as treating a large clientele of men who have sex with men -- were quinolone resistant. The authors said to their knowledge this is the highest resistance rate so far reported in North America.

Both the authors and infectious diseases experts who were not involved in the work were startled by how quickly and how high the rate climbed.

"There's no question this is a dramatic increase," said Dr. Andrew Simor, head of microbiology at Toronto's Sunnybrook Health Sciences Centre.

"We were sort of expecting this to occur and public health actually alerted physicians a year or two ago about the problem and therefore made recommendations to change treatment. So we were aware that this was a problem in Canada."

"But I don't think any of us were aware of the extent."

Before the resistance problem developed, fluoroquinolones were standard treatment of Neisseria gonorrhea. Ciprofloxacin -- often called Cipro -- is a well-known member of this class of antibiotics.

"The fluorquinolones were a wonderful treatment for it (gonorrhea), because it was a single pill that a person took," Simor said. "And of course very safe and very well tolerated. So that is I think a significant loss."

But when it became apparent a couple of years ago that resistant bacteria first reported in Southeast Asia had made their way to North America, public health officials in the United States and then Canada told doctors they should no longer use quinolones because they might not cure patients.

The recommendation was to switch to a cephalosporin drug such as cefixime, which is also a one-pill regime. But these antibiotics are members of the penicillin family and cannot be used by anyone with a penicillin allergy. There are alternatives, but there aren't as easy to use, Simor said.

And there are already hints that some gonorrhea strains may be developing resistance to the cephalosporins, a commentary published in the journal warned.

Dr. John Tapsall, of the World Health Organization's collaborating centre for sexually transmitted diseases in Sydney, Australia, noted that reports of treatment failure have started to emerge in Japan and Hong Kong. Treatment failure is a term used when an antibiotic fails to cure an infection because the bug is resistant to the drug.

The magnitude of the fluoroquinolone problem might be greater than the numbers in the Ontario study suggest, admitted senior author Dr. Susan Richardson, head of microbiology at Toronto's Hospital for Sick Children.

That's because increasing numbers of doctors and clinics that treat sexually transmitted infections are using urine tests to diagnose gonorrhea, said Richardson, who did the work in her capacity as a consultant to the Ontario Agency for Health Protection and Promotion.

While urine tests have the advantage of speed -- the results can be available within a day and treatment can be quickly administered -- they cannot be used to see if the bacteria causing the infection are resistant to antibiotics.

Drug resistance only be determined by old-fashion culture tests, where a doctor runs a swab inside the urethra or along the cervix to pick up bacteria, if they are present.

The authors said the findings underscore the need for a national sentinel surveillance system that will ensure some clinics continue to test by culture. Only by having that kind of system in place will public health authorities be able to keep on top of changes in the antibiotic resistance profiles of gonorrhea bacteria circulating in the country, she said.

Dr. Tom Wong, director of community acquired infections for the Public Health Agency of Canada, said the agency is working with provincial and territorial partners to try to put together a sentinel surveillance system.

"It takes time to actually set these up, negotiating the various aspects of setting up these sites," said Wong, who is also an author on the study.

"We are very hopeful that very soon we will have some of the pilot sites up and running. But at this time we are still actually trying to get all of those logistics set up."

Dr. Michael Rekart, director of the sexually transmitted infections and HIV program at the BC Centre for Disease Control, agreed that kind of system is essential.

"We really need these sentinel surveillance places that still do culture (tests) and can still look at resistance. If they hadn't looked at this, nobody would have anticipated these high levels of resistance."

"Just looking at my own data, I would have said, `No, no. It would never get that high.' And it has," Rekart said, noting resistance levels hover around five to 10 per cent in British Columbia, which made the switch away from fluorquinolones for gonorrhea several years ago.

"It shows what we don't know. And the fact that we really have to watch these things."