Abstract: 【Abstract】 Objective To analyze the genetic characteristics of three ceftriaxone-resistant Neisseria gonorrhoeae （N. gonorrhoeae） strains newly identified in a sexually transmitted disease clinic, and to follow up on the treatment outcomes of the infected patients. Methods This was a case series study. Patients with ceftriaxone-resistant N. gonorrhoeae infection were prospectively enrolled from the sexually transmitted disease clinic, Hospital for Skin Diseases, Chinese Academy of Medical Sciences between September 2021 and December 2022. Data on demographics, sexual behavior, and clinical characteristics were collected. After urethral swab collection, antimicrobial susceptibility was determined by the agar dilution method, and N. gonorrhoeae multiantigen sequence typing, multilocus sequence typing, and N. gonorrhoeae sequence typing for antimicrobial resistance were performed. Results All the 3 patients were heterosexual males of Han nationality, aged 22, 30, and 38 years, respectively. They reported no history of international travel and had acquired the infection through penile-vaginal contact. Cases 1 and 2 presented with urethral discharge and dysuria for 1 to 2 days, while Case 3 had persistent urethral symptoms lasting up to 30 days. Gonorrhea was confirmed by gonococcal culture and/or nucleic acid amplification testing. The minimum inhibitory concentrations of ceftriaxone against the 3 isolates ranged from 0.5 to 1 mg/L. All the 3 strains harbored the penA-60.001 gene, a known determinant of ceftriaxone resistance, and belonged to or were closely related to the internationally disseminated N. gonorrhoeae with multilocus sequence type ST1903. All the 3 patients were cured after a single intramuscular injection of either ceftriaxone 1 g or spectinomycin 2 g. Conclusion The internationally disseminated ceftriaxone-resistant N. gonorrhoeae with multilocus sequence type ST1903 has the potential for further transmission in Nanjing. Enhanced follow-up with test of cure should be implemented for patients with ceftriaxone-resistant N. gonorrhoeae infection, and the true relationship between resistance breakpoints and treatment outcomes requires further investigation.

Key words: Neisseria gonorrhoeae, Resistance to ceftriaxone, Treatment outcome