A recent cluster of gonorrhea cases on Oahu is setting off alarms nationally that the sexually transmitted disease may be developing resistance to the only drugs recommended to treat it.

Hawaii has a relatively low rate of gonorrhea, but the state’s active surveillance program, including antibiotic susceptibility testing of patient samples, has acted as a sentinel in the past as well, said Dr. Alan Katz, professor of public health at the University of Hawaii at Manoa.

“We are the ones that are most actively looking for this — that’s why we’re finding these antibiotic-resistant strains,” Katz said in a telephone interview Thursday from Atlanta, where he gave a presentation on the Hawaii cluster at the 2016 National STD Prevention Conference.

Local doctors cured all seven patients in the group with the standard therapy of two different antibiotics in April and May, said Katz, staff physician at the Diamond Head STD Clinic and a member of the state Board of Health.

But the patients’ laboratory specimens were the first cluster in the country to show decreased susceptibility to both drugs, according to Dr. Jonathan Mermin, director of the U.S. Centers for Disease Control’s National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention.

“Our last line of defense against gonorrhea is weakening,” Mermin said in a telephone news briefing Wednesday. “If resistance continues to increase and spread, current treatment will ultimately fail.”

He praised Hawaii’s detection and testing efforts. Honolulu participates in the Gonococcal Isolate Surveillance Project, which involves 25 cities across the country, and the state Department of Health also does its own statewide screening.

“In Hawaii, the system worked,” Mermin said. “Front-line providers diagnosed and treated infections, public health officials quickly detected resistance, and we were able to use cutting-edge lab technologies to track its spread and treat people who were linked to the cluster.”

Gonorrhea has been a daunting foe across the country, developing resistance to one treatment after another over the years, including penicillin and fluoroquinolones.

Now it seems that time may be running out on the only treatment option remaining: a combination of the antibiotics azithromycin and ceftriaxone. The Hawaii cluster showed high resistance to the former and reduced susceptibility to the latter.

Hawaii is on the front lines in part because of its proximity to Asia, “where we believe many of the resistant strains originate,” Katz said. None of the patients reported recent travel, however.

Because all seven patients — six men and one woman — were cured by the standard therapy, the underlying situation might have gone unnoticed if the state weren’t on the lookout for resistance.

“In Hawaii, 25 percent of all gonorrhea cases are identified by culture, and our state lab does antibiotic susceptibility testing,” Katz said. “That compares to less than 5 percent nationwide.”

“Had we not even looked for it,” he added, “no one would have even known.”

Gonorrhea is one of the most common sexually transmitted diseases, but many people don’t know they are infected. Its symptoms can include painful urination and a discharge from the penis or vagina, but most women have no symptoms. Mermin estimated that just half of cases nationwide are diagnosed.

If not treated, the disease can cause serious complications, including infertility, pelvic inflammatory disease and life-threatening ectopic pregnancy.

There were 73 reported gonorrhea cases per 100,000 Hawaii residents in 2014, well below the national average of 111.

“Our gonorrhea rates in Hawaii have always been below the national average,” Katz said. “It’s not a hot spot for cases.”

So far, there have been no treatment failures under the current drug regimen in the United States, according to the CDC.

There is some hope on the horizon. A new oral antibiotic, known as ETX0914, that is now in clinical trials has shown promise, according to Dr. Stephanie Taylor, professor of medicine at Louisiana State University and lead investigator, who also spoke at the conference.

Katz said, “If we reach that critical point where our dual therapy is failing, then we clearly need a backup.”

He added, “The drug that was presented at the conference would be a really novel way of approaching gonorrhea.”