CDC

Antibiotic-resistant gonorrhea light up this microscopic view.

The emergence of a strain of gonorrhea that can thwart the last antibiotic effective in treating the common sexually transmitted disease was bound to happen, experts say.

The new, super-resistant strain is called H041, and so far, only a handful of cases are known in Japan. But don't count on it staying that way. Experience has shown that once a resistant strain of gonorrhea appears, it steadily displaces those that can be killed with antibiotics.

It happened in the 1970s and 1980s with penicillin and tetracycline and more recently with a class of drugs called fluoroquinolones, such as Cipro.

 

The Centers for Disease Control and Prevention estimates that gonorrhea infects 700,000 Americans each year. It initially can cause painful urination and other symptoms, but can develop into chronic infections that can lead to infertility, joint damage and serious infections in babies born to infected mothers. People with gonorrhea are also at higher risk of getting HIV.

Researchers from Sweden and Japan reported on the discovery of H041 this week at the International Society for Sexually Transmitted Diseases in Quebec.

"An era of untreatable gonorrhea may have been initiated," the researchers warn in a published summary of their report. (You can find it on page A76 of this compilation of meeting abstracts.)

The ominous thing about H041 is that it is highly resistant, the researchers say, to cephalosporins â€" specifically the mainstay drugs cefixime and ceftriaxone. The CDC tells doctors to use these drugs in combination with another antibiotic â€" preferably azithromycin â€" to treat all gonorrhea these days.

The researchers say H041 is resistant to doses of ceftriaxone as much as eight times larger than seen with previously known gonorrhea strains, "and all other cephalosporins, as well as most other antimicrobials tested."

This unique antibiotic resistance is conferred by four newly discovered pinpoint mutations in amino acids making up the germ's genes.

The new report comes only a few days after the CDC put out a 10-year review of growing antibiotic resistance among US gonorrhea isolates, concluding "the eventual emergence of cephalosporin resistance appears likely."

The CDC report tracks an upward creep in what it calls minimum inhibitory concentrations, or MICs, to cephalosporin drugs. An elevated MIC means it takes a higher dose of the drug to kill the bug.

On the face of it, the 10-year increase in MIC levels doesn't look too alarming. For cefexime, the proportion of gonorrhea cases with elevated MIC levels went from 0.2 percent to 1.4 percent. And for ceftriaxone, it increased from 0.1 percent to 0.3 percent.

But it's the trend that's important. And resistance has grown much more in some parts of the country. For instance, in Honolulu, nearly 8 percent of all gonorrhea cases had elevated MIC levels last year, and in California it was nearly 5 percent.

The CDC is asking doctors to be alert to patients who aren't cured by standard doses of the recommended two-antibiotic cocktail, and especially to report any treatment failures. Such cases have recently been seen in Asia and Norway.

But the discovery of H041 foretells a different ballgame. This super-gonorrhea strain doesn't merely require higher doses of the most powerful antibiotic available. It might be entirely untreatable.

So the new bug calls for "enhanced disease control activities" to contain it, or at least delay its spread, the Swedish and Japanese teams says, and "ultimately, new drugs are essential... for efficacious gonorrhea treatment."