Gonorrhea is becoming more difficult to treat with readily available antibiotics, and it may be just a matter of time before a case shows up in California that doesn’t respond to any of the drugs currently in use.

This week, the world’s first case of drug-resistant gonorrhea – in a sex worker in Japan – was reported during a conference on sexually transmitted disease research. And last week the U.S. Centers for Disease Control and Prevention reported increased rates of gonorrhea cases that, while not quite resistant to antibiotics, are requiring larger doses to treat effectively.

Gonorrhea is still relatively easy to cure, and in the United States there has yet to be a patient who wasn’t successfully treated with antibiotics. but it’s likely that a strain of gonorrhea that doesn’t respond to the current treatments will begin circulating worldwide at some point – and doctors have run out of new antibiotics to replace the old ones.

“We’re not seeing any untreatable cases in the United States, but we’re seeing proof that what we’ve been worrying about for a while has actually happened” in Japan, said Dr. Susan Philip, director of STD prevention for the San Francisco Public Health Department. “If previous patterns hold true, drug resistance should slowly move its way toward us.”

S.F. has high rate

Gonorrhea is the second most common sexually transmitted infection after chlamydia, and San Francisco has among the highest rates of disease in the state and country. The city reported nearly 2,000 cases of gonorrhea in 2010, for a rate of 253 cases per 100,000 people; statewide, the rate is roughly 70 cases per 100,000 people.

While gonorrhea cases had been declining in recent years, San Francisco reported a 10 percent increase last year. there are several possible explanations for that increase – better and faster testing of STDs, for example – but epidemiologists say drug resistance could be a factor, too.

Gonorrhea is a bacterium that typically infects the male and female reproductive tracts, the rectum or the mouth. Symptoms can include a burning sensation when urinating and a discharge from the penis or vagina. but half of women, and a small percentage of men, have no symptoms, and if the infection is in the rectum or mouth, most people won’t know it.

Untreated gonorrhea can cause pelvic inflammatory disease and infertility in women, and people infected with gonorrhea are more susceptible to contracting HIV.

Antibiotics fading

For decades, gonorrhea was treated with penicillin but, like many other bacteria, gonorrhea mutates quickly and often, and eventually strains that didn’t respond to penicillin were circulating widely around the world.

Now that antibiotic isn’t working as well as it once did. Cephalosporin is still an effective treatment for gonorrhea, but over the past decade, public health labs have found more cases that require higher doses of the antibiotic to kill the bacteria.

In California, 4.5 percent of cases needed higher doses in 2010; there were no such cases in 2000. Higher doses are usually the first sign that the bacteria is building resistance to a drug.

“We’re down to our last class of antibiotics that we use to treat gonorrhea,” said Dr. Heidi Bauer, chief of program development and evaluation in the California public health department’s STD Control Branch. “One by one we’ve had to eliminate these other classes because this bacteria is so good at resistance.”