Whole-genome characterization of two azithromycin-resistant Neisseria gonorrhoeae ST1600 isolates from Busan, South Korea

다국어 초록 (Multilingual Abstract)

Azithromycin-resistant Neisseria gonorrhoeae poses a threat to the efficacy of gonorrhea treatment. We report the whole-genome characterization of two azithromycin-resistant N. gonorrhoeae ST1600 isolates collected in Busan, South Korea, in 2018 and 2019. Both isolates showed moderate azithromycin resistance (minimum inhibitory concentration 32 µg/mL) mediated by the 23S rRNA C2611T mutation in all four alleles and the -35A deletion in the mtrR promoter, while harboring distinct non-mosaic penA alleles without reduced susceptibility to extended-spectrum cephalosporins. Multilocus sequence typing classified both isolates as ST1600, which is related to ST7363. N. gonorrhoeae multi-antigen sequence typing assigned the 2018 isolate to ST16190, whereas the 2019 isolate represented a novel NG-MAST type closely related to ST16190 (differing by a single SNP in porB). Taken together, these data suggest a limited local transmission cluster with short-term persistence and microevolution, rather than widespread sustained clonal dissemination. Continued phenotypic and genomic surveillance is needed to monitor azithromycin resistance in N. gonorrhoeae and inform national treatment strategies.