“We are getting close to an era where [patients] may no longer respond” to the drug, said Dr. Katherine Hsu, medical director of the division of STD Prevention and HIV/AIDS at the Massachusetts Department of Public Health.

The discovery comes as sexually transmitted infections, especially gonorrhea, are soaring nationwide, and the ability of many microbes to outsmart the drugs used to kill them is a growing worry.

“We are down to very few – very few – options. The concern is we’ll get to a place where there are no options,” said Dr. Helen Boucher, chief academic officer of the Tufts Medicine health system and a member of the Presidential Advisory Council on Combating Antibiotic Resistant Bacteria. “This is a common infection in young healthy people. … There’s only one thing, and that one thing may not work any more.”

Dr. Ruanne Barnabas, chief of the Division of Infectious Diseases at Massachusetts General Hospital, called the strain’s discovery “significant.”

“But given how mobile we are as a global community, it is not surprising,” she said.

The Massachusetts news should serve as a heads-up to doctors and patients to take gonorrhea seriously and watch for signs of resistance, said Dr. Laura Bachmann, chief medical officer of the CDC’s Division of STD Prevention.

The Centers for Disease Control and Prevention and state health officials both sent alerts to providers Thursday afternoon. The Massachusetts alert said the finding is a warning that gonorrhea “is becoming less responsive to a limited arsenal of antibiotics.”

“The message to providers is, ‘hey, we’ve got to keep an eye on this,’” Bachmann said. “Antimicrobial resistance is an important and urgent public health threat.”

Still, the CDC has not changed its recommendations for testing and treatment of gonorrhea. Bachmann called it “reassuring” that both Massachusetts patients were cured with standard treatment, a one-time injection of ceftriaxone.

The strain is circulating in the Asia-Pacific region, and 10 cases were recently identified in the United Kingdom. The UK patients were also cured with ceftriaxone.

Should ceftriaxone stop working, there are alternative drugs but they have greater risks, or are less effective, doctors say.

“We want to maintain the options we have,” Barnabas said.

She added that a potential vaccine is in development.

A few new antibiotics that might work are also in the pipeline but “economic realities” have slowed progress, with companies that work on them going out of business, Boucher said.

Gonorrhea is a common and fast-spreading sexually transmitted infection. Its incidence increased 45 percent from 2016 to 2020, and more than half of those infected are between the ages of 15 and 24. In Massachusetts, laboratory-confirmed cases of gonorrhea have quadrupled from a low of 1,976 cases in 2009 to 8,133 in 2021. The bacteria that cause it infect the mucous membranes of the reproductive tract and the urethra in women and men, as well as the mouth, throat, eyes, and rectum.

In many cases, infected people have no symptoms, which is why the CDC recommends screening tests for sexually active people. When symptoms do occur, they can include painful urination and urethral or vaginal discharge.

If it goes untreated, gonorrhea can lead to pelvic inflammatory disease and infertility in women, and inflammation in the scrotum of men. In time it can spread to the blood and cause inflammation of tendons, joints, the brain or the heart.

The Massachusetts cases were discovered as part of a routine testing process. A primary care doctor conducted a standard test to identify gonorrhea and also had the sample cultured. After the culture identified the infection as gonorrhea, an isolate of the organism was sent to the State Laboratory, which performed further testing for drug resistance.

The sample showed signs of resistance, so the state sent it to the CDC for more advanced testing, which identified the worrisome genetic pattern: the bacteria were resistant to ciprofloxacin, penicillin, and tetracycline and had reduced susceptibility to ceftriaxone, cefixime, and azithromycin.

That prompted the health department to ask clinical laboratories in the same region to send it additional samples from around the same time period. Further testing at the CDC turned up the second case.

Health officials found no connection between the two cases, and Barnabas said there are surely more than two people infected with the new strain. But there is no information to indicate how widespread the new bug may be. A similar strain that was not quite as resistant was identified in Nevada in 2019 but never seen again.

“We cannot be sure without scaling up on our surveillance efforts,” Hsu said, and now is “pivotal proactive moment for public health.”

It’s possible that the strain is circulating elsewhere, Bachmann said. “This is why it’s so important for providers to have on their radar and public health departments to keep an eye out for treatment failures.”

“To prevent resistance,” Bachmann said, “it’s really important to identify gonorrhea quickly and treat it appropriately with the right drug at the right time and the right amount. That requires providers to be in tune to screening guidelines and appropriate treatment.”

The Massachusetts health department is asking providers to treat gonorrhea with high doses of ceftriaxone, perform cultures from symptomatic gonorrhea cases and follow protocols for submitting samples to the state lab, and test to make sure patients are cured after treatment. Additionally regular screening is recommended for sexually active women ages 24 and younger, women who are at increased risk, and sexually active men who have sex with men.

As for what individuals can do, Public Health Commissioner Margret Cooke offered this advice in a statement: “We urge all sexually active people to be regularly tested for sexually transmitted infections and to consider reducing the number of their sexual partners and increasing their use of condoms when having sex.”

Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her on Twitter @felicejfreyer.