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Antimicrobial resistance has, increasingly, limited treatment options for gonorrhea. The CDC recommends dual therapy with ceftriaxone and azithromycin. Few ceftriaxone-resistant isolates have been reported; only five have been reported worldwide through October 2017, most in Asia and none in North America. Investigators from Canada now report on a 23-year-old woman with genital gonorrhea first diagnosed with a nucleic acid amplification test (NAAT) and subsequently through culture.
Agar dilution antimicrobial susceptibility testing confirmed the isolate's resistance to ceftriaxone (minimum inhibitory concentration = 1 µg/mL), cefixime (MIC = 2 µg/mL), ciprofloxacin (MIC = 32 µg/mL), and tetracycline (MIC = 4 µg/mL) and susceptibility to azithromycin (MIC = 0.5 µg/mL). Although there are no formal breakpoints for cefixime or ceftriaxone resistance, the reported MICs are tenfold higher than what is considered reduced susceptibility. The patient reported having a sexual partner who had unprotected sex during a trip to China and Thailand before their month-long relationship. Molecular typing showed that the isolate carried the penA-60 allele, which was identical to that found in a ceftriaxone-resistant isolate identified in 2015 in Japan.
Lefebvre B et al. Ceftriaxone-resistant Neisseria gonorrhoeae, Canada, 2017. Emerg Infect Dis 2018 Feb 15; 24: [e-pub]. (http://dx.doi.org/10.3201/eid2402.171756)
Comment
Historically, antimicrobial resistance in Neisseria gonorrhoeae emerged in Asia and then spread to other countries including the U.S., usually first in Hawaii or the West Coast (N Engl J Med 2012; 366:485). Because gonorrhea is now mostly diagnosed through nonculture methods such as NAATs, surveillance for antimicrobial susceptibility is a public health priority. The CDC's GISP surveillance system, set up in 1986, has found fewer than 1.5% of isolates with reduced susceptibility to ceftriaxone (defined as MIC ≥0.125 µg/mL) and none with resistance, defined as an MIC ≥0.25 µg/mL (MMWR Morb Mortal Wkly Rep 2016; 65:1). Now that a ceftriaxone-resistant N. gonorrhoeae isolate has been identified in North America, clinicians must be vigilant and consider performing a culture in cases where the infection was acquired in Asia or, like in this case, when the patient had sexual contact with someone who had unprotected intercourse in Asia.