First US case of gonorrhea with novel resistance gene identified in Nevada
The first case of Neisseria gonorrhoeae with the emerging mosaic penA60 allele — which confers reduced susceptibility to cefixime and ceftriaxone — has been identified in the United States, according to a recent study.
“This isolate was captured and tested during routine procedures for” the CDC’s Gonococcal Isolate Surveillance Project (GISP), Michael A. Picker, PhD, a microbiology supervisor at the Southern Nevada Public Health Laboratory, told Healio.
Writing in MMWR, Picker and colleagues reported that the urethral isolate was collected in October 2019 from an HIV-negative, heterosexual man with penile discharge and dysuria. They said the man was treated with the then-recommended regimen of ceftriaxone given intramuscularly plus oral azithromycin. (That combination therapy is no longer recommended. In updated guidance, the CDC recommended recently that ceftriaxone be given alone — without azithromycin — for the treatment of uncomplicated gonorrhea. It recommends adding 100 mg of oral doxycycline — not azithromycin — twice a day for 7 days if chlamydial coinfection has not been ruled out.)
According to Picker and colleagues, nucleic acid amplification tests (NAATs) and cultures collected from the patient’s rectum and pharynx came back negative for N. gonorrhoeae.
After susceptibility results from the urethral isolate which demonstrated reduced susceptibility to cefixime and ceftriaxone but was still susceptible to azithromycin were confirmed by CDC in late November 2019, additional molecular testing by the CDC revealed the emerging mosaic penA60 allele, which was first identified in Japan in 2016 and then later identified in China, Canada, Denmark, Australia, France and the United Kingdom.
Picker and colleagues said the results of an investigation indicated that the man acquired the infection locally, “but the origin of the isolate remains unclear,” they wrote. The isolate’s minimum inhibitory concentration for ceftriaxone was the highest observed in the 34 years that GISP has been monitoring ceftriaxone and other antimicrobials susceptibilities, they reported.
To identify other cases of N. gonorrhoeae with the penA60 allele in the southern Nevada area, the Southern Nevada Health District provided the CDC with all N. gonorrhoeae NAAT-positive specimens from all of its clinics through December 2019. No additional cases were identified through culture independent molecular testing.
“The development of antibiotic resistance in N. gonorrhoeae, and, more generally, other bacterial pathogens, has the potential to negatively affect patient outcomes,” Picker said. “As such, the identification of this antibiotic-resistant strain of N. gonorrhoeae in Nevada in 2019 highlights the utility and importance of surveillance programs, like the GISP, as an effective tool in identifying emerging antimicrobial-resistant pathogens.”