Drug-Resistant Strain of Gonorrhea Spreads to North America

The incidence of drug-resistant gonorrhea infections has grown in the past several years; however, the majority of these infections have been reported outside of North America. Until now. According to a recent dispatch from the Centers for Disease Control and Prevention (CDC), a drug-resistant strain of Neisseria gonorrhoeae (N. gonorrhoeae ) was found in Canada this year.

As Contagion® reported in July 2017, gonorrhea, a sexually-transmitted disease caused by N. gonorrhoeae bacteria, is on its way to becoming untreatable. According to the World Health Organization (WHO) Global Gonococcal Antimicrobial Surveillance Programme (WHO GASP), an estimated 78 million individuals are infected with gonorrhea on an annual basis, and the number of cases that are resistant to currently available antibiotics continues to grow. Teodora Wi, MD, Medical Officer, Human Reproduction at WHO, explained in a news release, “The bacteria that cause gonorrhea are particularly smart. Every time we use a new class of antibiotics to treat the infection, the bacteria evolve to resist them.”

One of the antibiotics of last resort that clinicians use to treat gonorrhea is ceftriaxone. The drug is part of a dual therapy with azithromycin that is recommended in Canada for the treatment of gonorrhea. According to the CDC dispatch, “As of October 15, 2017, only 5 ceftriaxone-resistant N. gonorrhoeae isolates had been reported worldwide (MIC range 0.5—2 mg/L).”

The ceftriaxone-resistant isolate that was discovered in Canada was recovered from a 23-year-old woman who had a positive N. gonorrhoeae nucleic acid amplification test (NAAT) result on January 17, 2017. The woman did not exhibit any symptoms of infection. She reported that she had been in a month-long sexual relationship with a man 60 days before the sexually transmitted infection (STI) screening. Her partner was also asymptomatic and a urinary NAAT screening result came up negative for N. gonorrhoeae. Although the partner reported that he had not had sex with men or a sex worker, he stated that he did engage in unprotected sexual activity during a prior (November 2016) trip to China and Thailand. The trip occurred prior to his relationship with the female patient. Subsequent follow-up tests on the partner (February 2017) also yielded negative results. In addition, test results for the patient’s prior partner (5 months earlier) came back negative for N. gonorrhoeae.

The patient was advised to receive counseling at a sexually-transmitted infections clinic and there she was given a prescription for a single dose of cefixime 800 mg and azithromycin 1 g, which is the recommended therapy according to Québec STI Treatment Guidelines. According to the dispatch, “Because the patient was from a low-prevalence population, the healthcare provider decided to perform a genital gonorrhea culture. The culture was positive for N. gonorrhoeae (no. GC063564/47707), thus confirming the positive NAAT result.”

Through the use of antimicrobial susceptibility testing, investigators found that the isolate was not susceptible to ceftriaxone and cefixime, but it was susceptible to azithromycin. Therefore, it was requested that the patient return for a follow-up visit with the doctor. When she came for the follow-up visit on February 7, 2017, the patient was “prescribed empirically a single 2-g dose of azithromycin,” according to the dispatch. Subsequent NAAT test and cervical culture completed at this visit yielded negative results for N. gonorrhoeae, which indicated that the initial treatment with cefixime plus azithromycin was successful.

Although the treatment was successful, it is still alarming that the isolate obtained from the patient contained an allele that had been formerly reported only in Japan in 2015. To this end, the authors write that, “Epidemiologic information suggests international spread of a penA allele associated with high-level ceftriaxone resistance. Antimicrobial susceptibility surveillance successfully identified this novel isolate introduced into Canada and prompted public health officials to rapidly conduct an investigation to prevent further spread in the community. In an era of multidrug-resistant gonorrhea, ongoing antimicrobial susceptibility surveillance of N. gonorrhoeae is critical to support treatment guidelines, public health intervention, and protection."